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Posted to commits@cassandra.apache.org by ty...@apache.org on 2015/05/19 18:37:26 UTC
svn commit: r1680337 - /cassandra/site/publish/doc/cql3/CQL-2.2.html
Author: tylerhobbs
Date: Tue May 19 16:37:26 2015
New Revision: 1680337
URL: http://svn.apache.org/r1680337
Log:
Add CQL3 docs for Cassandra 2.2
Added:
cassandra/site/publish/doc/cql3/CQL-2.2.html
Added: cassandra/site/publish/doc/cql3/CQL-2.2.html
URL: http://svn.apache.org/viewvc/cassandra/site/publish/doc/cql3/CQL-2.2.html?rev=1680337&view=auto
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+<?xml version='1.0' encoding='utf-8' ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"/><title>CQL</title></head><body><p><link rel="StyleSheet" href="CQL.css" type="text/css" media="screen"></p><h1 id="CassandraQueryLanguageCQLv3.3.0">Cassandra Query Language (CQL) v3.3.0</h1><span id="tableOfContents"><ol style="list-style: none;"><li><a href="CQL.html#CassandraQueryLanguageCQLv3.3.0">Cassandra Query Language (CQL) v3.3.0</a><ol style="list-style: none;"><li><a href="CQL.html#CQLSyntax">CQL Syntax</a><ol style="list-style: none;"><li><a href="CQL.html#Preamble">Preamble</a></li><li><a href="CQL.html#Conventions">Conventions</a></li><li><a href="CQL.html#identifiers">Identifiers and keywords</a></li><li><a href="CQL.html#constants">Constants</a></li><li><a href="CQL.html#Comments">Comments</a></l
i><li><a href="CQL.html#statements">Statements</a></li><li><a href="CQL.html#preparedStatement">Prepared Statement</a></li></ol></li><li><a href="CQL.html#dataDefinition">Data Definition</a><ol style="list-style: none;"><li><a href="CQL.html#createKeyspaceStmt">CREATE KEYSPACE</a></li><li><a href="CQL.html#useStmt">USE</a></li><li><a href="CQL.html#alterKeyspaceStmt">ALTER KEYSPACE</a></li><li><a href="CQL.html#dropKeyspaceStmt">DROP KEYSPACE</a></li><li><a href="CQL.html#createTableStmt">CREATE TABLE</a></li><li><a href="CQL.html#alterTableStmt">ALTER TABLE</a></li><li><a href="CQL.html#dropTableStmt">DROP TABLE</a></li><li><a href="CQL.html#truncateStmt">TRUNCATE</a></li><li><a href="CQL.html#createIndexStmt">CREATE INDEX</a></li><li><a href="CQL.html#dropIndexStmt">DROP INDEX</a></li><li><a href="CQL.html#createTypeStmt">CREATE TYPE</a></li><li><a href="CQL.html#alterTypeStmt">ALTER TYPE</a></li><li><a href="CQL.html#dropTypeStmt">DROP TYPE</a></li><li><a href="CQL.html#createTri
ggerStmt">CREATE TRIGGER</a></li><li><a href="CQL.html#dropTriggerStmt">DROP TRIGGER</a></li><li><a href="CQL.html#createFunctionStmt">CREATE FUNCTION</a></li><li><a href="CQL.html#dropFunctionStmt">DROP FUNCTION</a></li><li><a href="CQL.html#createAggregateStmt">CREATE AGGREGATE</a></li><li><a href="CQL.html#dropAggregateStmt">DROP AGGREGATE</a></li></ol></li><li><a href="CQL.html#dataManipulation">Data Manipulation</a><ol style="list-style: none;"><li><a href="CQL.html#insertStmt">INSERT</a></li><li><a href="CQL.html#updateStmt">UPDATE</a></li><li><a href="CQL.html#deleteStmt">DELETE</a></li><li><a href="CQL.html#batchStmt">BATCH</a></li></ol></li><li><a href="CQL.html#queries">Queries</a><ol style="list-style: none;"><li><a href="CQL.html#selectStmt">SELECT</a></li></ol></li><li><a href="CQL.html#types">Data Types</a><ol style="list-style: none;"><li><a href="CQL.html#usingtimestamps">Working with timestamps</a></li><li><a href="CQL.html#usingdates">Working with dates</a></li><li
><a href="CQL.html#usingtime">Working with time</a></li><li><a href="CQL.html#counters">Counters</a></li><li><a href="CQL.html#collections">Working with collections</a></li></ol></li><li><a href="CQL.html#functions">Functions</a><ol style="list-style: none;"><li><a href="CQL.html#tokenFun">Token</a></li><li><a href="CQL.html#uuidFun">Uuid</a></li><li><a href="CQL.html#timeuuidFun">Timeuuid functions</a></li><li><a href="CQL.html#blobFun">Blob conversion functions</a></li></ol></li><li><a href="CQL.html#udfs">User-Defined Functions</a></li><li><a href="CQL.html#udas">User-Defined Aggregates</a></li><li><a href="CQL.html#json">JSON Support</a><ol style="list-style: none;"><li><a href="CQL.html#selectJson">SELECT JSON</a></li><li><a href="CQL.html#insertJson">INSERT JSON</a></li><li><a href="CQL.html#jsonEncoding">JSON Encoding of Cassandra Data Types</a></li><li><a href="CQL.html#fromJson">The fromJson() Function</a></li><li><a href="CQL.html#toJson">The toJson() Function</a></li></ol
></li><li><a href="CQL.html#appendixA">Appendix A: CQL Keywords</a></li><li><a href="CQL.html#appendixB">Appendix B: CQL Reserved Types</a></li><li><a href="CQL.html#changes">Changes</a><ol style="list-style: none;"><li><a href="CQL.html#a3.3.0">3.3.0</a></li><li><a href="CQL.html#a3.2.0">3.2.0</a></li><li><a href="CQL.html#a3.1.7">3.1.7</a></li><li><a href="CQL.html#a3.1.6">3.1.6</a></li><li><a href="CQL.html#a3.1.5">3.1.5</a></li><li><a href="CQL.html#a3.1.4">3.1.4</a></li><li><a href="CQL.html#a3.1.3">3.1.3</a></li><li><a href="CQL.html#a3.1.2">3.1.2</a></li><li><a href="CQL.html#a3.1.1">3.1.1</a></li><li><a href="CQL.html#a3.1.0">3.1.0</a></li><li><a href="CQL.html#a3.0.5">3.0.5</a></li><li><a href="CQL.html#a3.0.4">3.0.4</a></li><li><a href="CQL.html#a3.0.3">3.0.3</a></li><li><a href="CQL.html#a3.0.2">3.0.2</a></li><li><a href="CQL.html#a3.0.1">3.0.1</a></li></ol></li><li><a href="CQL.html#Versioning">Versioning</a></li></ol></li></ol></span><h2 id="CQLSyntax">CQL Syntax</h2><h
3 id="Preamble">Preamble</h3><p>This document describes the Cassandra Query Language (CQL) version 3. CQL v3 is not backward compatible with CQL v2 and differs from it in numerous ways. Note that this document describes the last version of the languages. However, the <a href="#changes">changes</a> section provides the diff between the different versions of CQL v3.</p><p>CQL v3 offers a model very close to SQL in the sense that data is put in <em>tables</em> containing <em>rows</em> of <em>columns</em>. For that reason, when used in this document, these terms (tables, rows and columns) have the same definition than they have in SQL. But please note that as such, they do <strong>not</strong> refer to the concept of rows and columns found in the internal implementation of Cassandra and in the thrift and CQL v2 API.</p><h3 id="Conventions">Conventions</h3><p>To aid in specifying the CQL syntax, we will use the following conventions in this document:</p><ul><li>Language rules will be giv
en in a <a href="http://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form">BNF</a> -like notation:</li></ul><pre class="syntax"><pre><start> ::= TERMINAL <non-terminal1> <non-terminal1>
+</pre></pre><ul><li>Nonterminal symbols will have <code><angle brackets></code>.</li><li>As additional shortcut notations to BNF, we’ll use traditional regular expression’s symbols (<code>?</code>, <code>+</code> and <code>*</code>) to signify that a given symbol is optional and/or can be repeated. We’ll also allow parentheses to group symbols and the <code>[<characters>]</code> notation to represent any one of <code><characters></code>.</li><li>The grammar is provided for documentation purposes and leave some minor details out. For instance, the last column definition in a <code>CREATE TABLE</code> statement is optional but supported if present even though the provided grammar in this document suggest it is not supported. </li><li>Sample code will be provided in a code block:</li></ul><pre class="sample"><pre>SELECT sample_usage FROM cql;
+</pre></pre><ul><li>References to keywords or pieces of CQL code in running text will be shown in a <code>fixed-width font</code>.</li></ul><h3 id="identifiers">Identifiers and keywords</h3><p>The CQL language uses <em>identifiers</em> (or <em>names</em>) to identify tables, columns and other objects. An identifier is a token matching the regular expression <code lang="a-zA-Z">[a-zA-Z0-9_]</code><code>*</code>.</p><p>A number of such identifiers, like <code>SELECT</code> or <code>WITH</code>, are <em>keywords</em>. They have a fixed meaning for the language and most are reserved. The list of those keywords can be found in <a href="#appendixA">Appendix A</a>.</p><p>Identifiers and (unquoted) keywords are case insensitive. Thus <code>SELECT</code> is the same than <code>select</code> or <code>sElEcT</code>, and <code>myId</code> is the same than <code>myid</code> or <code>MYID</code> for instance. A convention often used (in particular by the samples of this documentation) is to use u
pper case for keywords and lower case for other identifiers.</p><p>There is a second kind of identifiers called <em>quoted identifiers</em> defined by enclosing an arbitrary sequence of characters in double-quotes(<code>"</code>). Quoted identifiers are never keywords. Thus <code>"select"</code> is not a reserved keyword and can be used to refer to a column, while <code>select</code> would raise a parse error. Also, contrarily to unquoted identifiers and keywords, quoted identifiers are case sensitive (<code>"My Quoted Id"</code> is <em>different</em> from <code>"my quoted id"</code>). A fully lowercase quoted identifier that matches <code lang="a-zA-Z">[a-zA-Z0-9_]</code><code>*</code> is equivalent to the unquoted identifier obtained by removing the double-quote (so <code>"myid"</code> is equivalent to <code>myid</code> and to <code>myId</code> but different from <code>"myId"</code>). Inside a quoted identifier, the double-quote character can be repeated to escape it, so <code>"fo
o "" bar"</code> is a valid identifier.</p><h3 id="constants">Constants</h3><p>CQL defines the following kind of <em>constants</em>: strings, integers, floats, booleans, uuids and blobs:</p><ul><li>A string constant is an arbitrary sequence of characters characters enclosed by single-quote(<code>'</code>). One can include a single-quote in a string by repeating it, e.g. <code>'It''s raining today'</code>. Those are not to be confused with quoted identifiers that use double-quotes.</li><li>An integer constant is defined by <code>'-'?[0-9]+</code>.</li><li>A float constant is defined by <code>'-'?[0-9]+('.'[0-9]*)?([eE][+-]?[0-9+])?</code>. On top of that, <code>NaN</code> and <code>Infinity</code> are also float constants.</li><li>A boolean constant is either <code>true</code> or <code>false</code> up to case-insensitivity (i.e. <code>True</code> is a valid boolean constant).</li><li>A <a href="http://en.wikipedia.org/wiki/Universally_unique_identifier">UUID</a> constant is defined b
y <code>hex{8}-hex{4}-hex{4}-hex{4}-hex{12}</code> where <code>hex</code> is an hexadecimal character, e.g. <code>[0-9a-fA-F]</code> and <code>{4}</code> is the number of such characters.</li><li>A blob constant is an hexadecimal number defined by <code>0[xX](hex)+</code> where <code>hex</code> is an hexadecimal character, e.g. <code>[0-9a-fA-F]</code>.</li></ul><p>For how these constants are typed, see the <a href="#types">data types section</a>.</p><h3 id="Comments">Comments</h3><p>A comment in CQL is a line beginning by either double dashes (<code>--</code>) or double slash (<code>//</code>).</p><p>Multi-line comments are also supported through enclosure within <code>/*</code> and <code>*/</code> (but nesting is not supported).</p><pre class="sample"><pre>-- This is a comment
+// This is a comment too
+/* This is
+ a multi-line comment */
+</pre></pre><h3 id="statements">Statements</h3><p>CQL consists of statements. As in SQL, these statements can be divided in 3 categories:</p><ul><li>Data definition statements, that allow to set and change the way data is stored.</li><li>Data manipulation statements, that allow to change data</li><li>Queries, to look up data</li></ul><p>All statements end with a semicolon (<code>;</code>) but that semicolon can be omitted when dealing with a single statement. The supported statements are described in the following sections. When describing the grammar of said statements, we will reuse the non-terminal symbols defined below:</p><pre class="syntax"><pre><identifier> ::= any quoted or unquoted identifier, excluding reserved keywords
+ <tablename> ::= (<identifier> '.')? <identifier>
+
+ <string> ::= a string constant
+ <integer> ::= an integer constant
+ <float> ::= a float constant
+ <number> ::= <integer> | <float>
+ <uuid> ::= a uuid constant
+ <boolean> ::= a boolean constant
+ <hex> ::= a blob constant
+
+ <constant> ::= <string>
+ | <number>
+ | <uuid>
+ | <boolean>
+ | <hex>
+ <variable> ::= '?'
+ | ':' <identifier>
+ <term> ::= <constant>
+ | <collection-literal>
+ | <variable>
+ | <function> '(' (<term> (',' <term>)*)? ')'
+
+ <collection-literal> ::= <map-literal>
+ | <set-literal>
+ | <list-literal>
+ <map-literal> ::= '{' ( <term> ':' <term> ( ',' <term> ':' <term> )* )? '}'
+ <set-literal> ::= '{' ( <term> ( ',' <term> )* )? '}'
+ <list-literal> ::= '[' ( <term> ( ',' <term> )* )? ']'
+
+ <function> ::= <ident>
+
+ <properties> ::= <property> (AND <property>)*
+ <property> ::= <identifier> '=' ( <identifier> | <constant> | <map-literal> )
+</pre></pre><p><br/>Please note that not every possible productions of the grammar above will be valid in practice. Most notably, <code><variable></code> and nested <code><collection-literal></code> are currently not allowed inside <code><collection-literal></code>.</p><p>A <code><variable></code> can be either anonymous (a question mark (<code>?</code>)) or named (an identifier preceded by <code>:</code>). Both declare a bind variables for <a href="#preparedStatement">prepared statements</a>. The only difference between an anymous and a named variable is that a named one will be easier to refer to (how exactly depends on the client driver used).</p><p>The <code><properties></code> production is use by statement that create and alter keyspaces and tables. Each <code><property></code> is either a <em>simple</em> one, in which case it just has a value, or a <em>map</em> one, in which case it’s value is a map grouping sub-options. The following will refer to one
or the other as the <em>kind</em> (<em>simple</em> or <em>map</em>) of the property.</p><p>A <code><tablename></code> will be used to identify a table. This is an identifier representing the table name that can be preceded by a keyspace name. The keyspace name, if provided, allow to identify a table in another keyspace than the currently active one (the currently active keyspace is set through the <a href=":#useStmt"><tt>USE</tt></a> statement).</p><p>For supported <code><function></code>, see the section on <a href="#functions">functions</a>.</p><p>Strings can be either enclosed with single quotes or two dollar characters. The second syntax has been introduced to allow strings that contain single quotes. Typical candidates for such strings are source code fragments for user-defined functions.</p><p><i>Sample:</i></p><pre class="sample"><pre> 'some string value'
+
+ $$double-dollar string can contain single ' quotes$$
+</pre></pre><p></p><h3 id="preparedStatement">Prepared Statement</h3><p>CQL supports <em>prepared statements</em>. Prepared statement is an optimization that allows to parse a query only once but execute it multiple times with different concrete values.</p><p>In a statement, each time a column value is expected (in the data manipulation and query statements), a <code><variable></code> (see above) can be used instead. A statement with bind variables must then be <em>prepared</em>. Once it has been prepared, it can executed by providing concrete values for the bind variables. The exact procedure to prepare a statement and execute a prepared statement depends on the CQL driver used and is beyond the scope of this document.</p><p>In addition to providing column values, bind markers may be used to provide values for <code>LIMIT</code>, <code>TIMESTAMP</code>, and <code>TTL</code> clauses. If anonymous bind markers are used, the names for the query parameters will be <code>[limit]</co
de>, <code>[timestamp]</code>, and <code>[ttl]</code>, respectively.</p><h2 id="dataDefinition">Data Definition</h2><h3 id="createKeyspaceStmt">CREATE KEYSPACE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><create-keyspace-stmt> ::= CREATE KEYSPACE (IF NOT EXISTS)? <identifier> WITH <properties>
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>CREATE KEYSPACE Excelsior
+ WITH replication = {'class': 'SimpleStrategy', 'replication_factor' : 3};
+
+CREATE KEYSPACE Excalibur
+ WITH replication = {'class': 'NetworkTopologyStrategy', 'DC1' : 1, 'DC2' : 3}
+ AND durable_writes = false;
+</pre></pre><p><br/>The <code>CREATE KEYSPACE</code> statement creates a new top-level <em>keyspace</em>. A keyspace is a namespace that defines a replication strategy and some options for a set of tables. Valid keyspaces names are identifiers composed exclusively of alphanumerical characters and whose length is lesser or equal to 32. Note that as identifiers, keyspace names are case insensitive: use a quoted identifier for case sensitive keyspace names.</p><p>The supported <code><properties></code> for <code>CREATE KEYSPACE</code> are:</p><table><tr><th>name </th><th>kind </th><th>mandatory </th><th>default </th><th>description</th></tr><tr><td><code>replication</code> </td><td><em>map</em> </td><td>yes </td><td> </td><td>The replication strategy and options to use for the keyspace. </td></tr><tr><td><code>durable_writes</code> </td><td><em>simple</em> </td><td>no </td><td>true </td><td>Whether to use the commit log for updates on
this keyspace (disable this option at your own risk!). </td></tr></table><p>The <code>replication</code> <code><property></code> is mandatory. It must at least contains the <code>'class'</code> sub-option which defines the replication strategy class to use. The rest of the sub-options depends on that replication strategy class. By default, Cassandra support the following <code>'class'</code>:</p><ul><li><code>'SimpleStrategy'</code>: A simple strategy that defines a simple replication factor for the whole cluster. The only sub-options supported is <code>'replication_factor'</code> to define that replication factor and is mandatory.</li><li><code>'NetworkTopologyStrategy'</code>: A replication strategy that allows to set the replication factor independently for each data-center. The rest of the sub-options are key-value pairs where each time the key is the name of a datacenter and the value the replication factor for that data-center.</li><li><code>'OldNetworkTopologyStrategy'</co
de>: A legacy replication strategy. You should avoid this strategy for new keyspaces and prefer <code>'NetworkTopologyStrategy'</code>.</li></ul><p>Attempting to create an already existing keyspace will return an error unless the <code>IF NOT EXISTS</code> option is used. If it is used, the statement will be a no-op if the keyspace already exists.</p><h3 id="useStmt">USE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><use-stmt> ::= USE <identifier>
+</pre></pre><p><i>Sample:</i></p><pre class="sample"><pre>USE myApp;
+</pre></pre><p>The <code>USE</code> statement takes an existing keyspace name as argument and set it as the per-connection current working keyspace. All subsequent keyspace-specific actions will be performed in the context of the selected keyspace, unless <a href="#statements">otherwise specified</a>, until another USE statement is issued or the connection terminates.</p><h3 id="alterKeyspaceStmt">ALTER KEYSPACE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><create-keyspace-stmt> ::= ALTER KEYSPACE <identifier> WITH <properties>
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>ALTER KEYSPACE Excelsior
+ WITH replication = {'class': 'SimpleStrategy', 'replication_factor' : 4};
+
+</pre></pre><p><br/>The <code>ALTER KEYSPACE</code> statement alters the properties of an existing keyspace. The supported <code><properties></code> are the same as for the <a href="#createKeyspaceStmt"><code>CREATE KEYSPACE</code></a> statement.</p><h3 id="dropKeyspaceStmt">DROP KEYSPACE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><drop-keyspace-stmt> ::= DROP KEYSPACE ( IF EXISTS )? <identifier>
+</pre></pre><p><i>Sample:</i></p><pre class="sample"><pre>DROP KEYSPACE myApp;
+</pre></pre><p>A <code>DROP KEYSPACE</code> statement results in the immediate, irreversible removal of an existing keyspace, including all column families in it, and all data contained in those column families.</p><p>If the keyspace does not exists, the statement will return an error, unless <code>IF EXISTS</code> is used in which case the operation is a no-op.</p><h3 id="createTableStmt">CREATE TABLE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><create-table-stmt> ::= CREATE ( TABLE | COLUMNFAMILY ) ( IF NOT EXISTS )? <tablename>
+ '(' <column-definition> ( ',' <column-definition> )* ')'
+ ( WITH <option> ( AND <option>)* )?
+
+<column-definition> ::= <identifier> <type> ( STATIC )? ( PRIMARY KEY )?
+ | PRIMARY KEY '(' <partition-key> ( ',' <identifier> )* ')'
+
+<partition-key> ::= <identifier>
+ | '(' <identifier> (',' <identifier> )* ')'
+
+<option> ::= <property>
+ | COMPACT STORAGE
+ | CLUSTERING ORDER
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>CREATE TABLE monkeySpecies (
+ species text PRIMARY KEY,
+ common_name text,
+ population varint,
+ average_size int
+) WITH comment='Important biological records'
+ AND read_repair_chance = 1.0;
+
+CREATE TABLE timeline (
+ userid uuid,
+ posted_month int,
+ posted_time uuid,
+ body text,
+ posted_by text,
+ PRIMARY KEY (userid, posted_month, posted_time)
+) WITH compaction = { 'class' : 'LeveledCompactionStrategy' };
+</pre></pre><p><br/>The <code>CREATE TABLE</code> statement creates a new table. Each such table is a set of <em>rows</em> (usually representing related entities) for which it defines a number of properties. A table is defined by a <a href="#createTableName">name</a>, it defines the <a href="#createTableColumn"><it>columns</it></a> composing rows of the table and have a number of <a href="#createTableOptions">options</a>. Note that the <code>CREATE COLUMNFAMILY</code> syntax is supported as an alias for <code>CREATE TABLE</code> (for historical reasons).</p><p>Attempting to create an already existing table will return an error unless the <code>IF NOT EXISTS</code> option is used. If it is used, the statement will be a no-op if the table already exists.</p><h4 id="createTableName"><code><tablename></code></h4><p>Valid table names are the same as valid <a href="#createKeyspaceStmt">keyspace names</a> (up to 32 characters long alphanumerical identifiers). If the table name is provid
ed alone, the table is created within the current keyspace (see <a href="#useStmt"><tt>USE</tt></a>), but if it is prefixed by an existing keyspace name (see <a href="#statements"><code><tablename></code></a> grammar), it is created in the specified keyspace (but does <strong>not</strong> change the current keyspace).</p><h4 id="createTableColumn"><code><column-definition></code></h4><p>A <code>CREATE TABLE</code> statement defines the columns that rows of the table can have. A <em>column</em> is defined by its name (an identifier) and its type (see the <a href="#types">data types</a> section for more details on allowed types and their properties).</p><p>Within a table, a row is uniquely identified by its <code>PRIMARY KEY</code> (or more simply the key), and hence all table definitions <strong>must</strong> define a PRIMARY KEY (and only one). A <code>PRIMARY KEY</code> is composed of one or more of the columns defined in the table. If the <code>PRIMARY KEY</code> is only one
column, this can be specified directly after the column definition. Otherwise, it must be specified by following <code>PRIMARY KEY</code> by the comma-separated list of column names composing the key within parenthesis. Note that:</p><pre class="sample"><pre>CREATE TABLE t (
+ k int PRIMARY KEY,
+ other text
+)
+</pre></pre><p>is equivalent to</p><pre class="sample"><pre>CREATE TABLE t (
+ k int,
+ other text,
+ PRIMARY KEY (k)
+)
+</pre></pre><h4 id="createTablepartitionClustering">Partition key and clustering columns</h4><p>In CQL, the order in which columns are defined for the <code>PRIMARY KEY</code> matters. The first column of the key is called the <i>partition key</i>. It has the property that all the rows sharing the same partition key (even across table in fact) are stored on the same physical node. Also, insertion/update/deletion on rows sharing the same partition key for a given table are performed <i>atomically</i> and in <i>isolation</i>. Note that it is possible to have a composite partition key, i.e. a partition key formed of multiple columns, using an extra set of parentheses to define which columns forms the partition key.</p><p>The remaining columns of the <code>PRIMARY KEY</code> definition, if any, are called __clustering columns. On a given physical node, rows for a given partition key are stored in the order induced by the clustering columns, making the retrieval of rows in that clusterin
g order particularly efficient (see <a href="#selectStmt"><tt>SELECT</tt></a>).</p><h4 id="createTableStatic"><code>STATIC</code> columns</h4><p>Some columns can be declared as <code>STATIC</code> in a table definition. A column that is static will be “shared” by all the rows belonging to the same partition (having the same partition key). For instance, in:</p><pre class="sample"><pre>CREATE TABLE test (
+ pk int,
+ t int,
+ v text,
+ s text static,
+ PRIMARY KEY (pk, t)
+);
+INSERT INTO test(pk, t, v, s) VALUES (0, 0, 'val0', 'static0');
+INSERT INTO test(pk, t, v, s) VALUES (0, 1, 'val1', 'static1');
+SELECT * FROM test WHERE pk=0 AND t=0;
+</pre></pre><p>the last query will return <code>'static1'</code> as value for <code>s</code>, since <code>s</code> is static and thus the 2nd insertion modified this “shared” value. Note however that static columns are only static within a given partition, and if in the example above both rows where from different partitions (i.e. if they had different value for <code>pk</code>), then the 2nd insertion would not have modified the value of <code>s</code> for the first row.</p><p>A few restrictions applies to when static columns are allowed:</p><ul><li>tables with the <code>COMPACT STORAGE</code> option (see below) cannot have them</li><li>a table without clustering columns cannot have static columns (in a table without clustering columns, every partition has only one row, and so every column is inherently static).</li><li>only non <code>PRIMARY KEY</code> columns can be static</li></ul><h4 id="createTableOptions"><code><option></code></h4><p>The <code>CREATE TABLE</cod
e> statement supports a number of options that controls the configuration of a new table. These options can be specified after the <code>WITH</code> keyword.</p><p>The first of these option is <code>COMPACT STORAGE</code>. This option is mainly targeted towards backward compatibility for definitions created before CQL3 (see <a href="http://www.datastax.com/dev/blog/thrift-to-cql3">www.datastax.com/dev/blog/thrift-to-cql3</a> for more details). The option also provides a slightly more compact layout of data on disk but at the price of diminished flexibility and extensibility for the table. Most notably, <code>COMPACT STORAGE</code> tables cannot have collections nor static columns and a <code>COMPACT STORAGE</code> table with at least one clustering column supports exactly one (as in not 0 nor more than 1) column not part of the <code>PRIMARY KEY</code> definition (which imply in particular that you cannot add nor remove columns after creation). For those reasons, <code>COMPACT STO
RAGE</code> is not recommended outside of the backward compatibility reason evoked above.</p><p>Another option is <code>CLUSTERING ORDER</code>. It allows to define the ordering of rows on disk. It takes the list of the clustering column names with, for each of them, the on-disk order (Ascending or descending). Note that this option affects <a href="#selectOrderBy">what <code>ORDER BY</code> are allowed during <code>SELECT</code></a>.</p><p>Table creation supports the following other <code><property></code>:</p><table><tr><th>option </th><th>kind </th><th>default </th><th>description</th></tr><tr><td><code>comment</code> </td><td><em>simple</em> </td><td>none </td><td>A free-form, human-readable comment.</td></tr><tr><td><code>read_repair_chance</code> </td><td><em>simple</em> </td><td>0.1 </td><td>The probability with which to query extra nodes (e.g. more nodes than required by the consistency level) for the purpos
e of read repairs.</td></tr><tr><td><code>dclocal_read_repair_chance</code> </td><td><em>simple</em> </td><td>0 </td><td>The probability with which to query extra nodes (e.g. more nodes than required by the consistency level) belonging to the same data center than the read coordinator for the purpose of read repairs.</td></tr><tr><td><code>gc_grace_seconds</code> </td><td><em>simple</em> </td><td>864000 </td><td>Time to wait before garbage collecting tombstones (deletion markers).</td></tr><tr><td><code>bloom_filter_fp_chance</code> </td><td><em>simple</em> </td><td>0.00075 </td><td>The target probability of false positive of the sstable bloom filters. Said bloom filters will be sized to provide the provided probability (thus lowering this value impact the size of bloom filters in-memory and on-disk)</td></tr><tr><td><code>compaction</code> </td><td><em>map</em> </td><td><em>see below</em> </td><td>The compaction options to use, se
e below.</td></tr><tr><td><code>compression</code> </td><td><em>map</em> </td><td><em>see below</em> </td><td>Compression options, see below. </td></tr><tr><td><code>caching</code> </td><td><em>simple</em> </td><td>keys_only </td><td>Whether to cache keys (“key cache”) and/or rows (“row cache”) for this table. Valid values are: <code>all</code>, <code>keys_only</code>, <code>rows_only</code> and <code>none</code>. </td></tr><tr><td><code>default_time_to_live</code> </td><td><em>simple</em> </td><td>0 </td><td>The default expiration time (“TTL”) in seconds for a table.</td></tr></table><h4 id="compactionOptions"><code>compaction</code> options</h4><p>The <code>compaction</code> property must at least define the <code>'class'</code> sub-option, that defines the compaction strategy class to use. The default supported class are <code>'SizeTieredCompactionStrategy'</code> and <code>'LeveledCompacti
onStrategy'</code>. Custom strategy can be provided by specifying the full class name as a <a href="#constants">string constant</a>. The rest of the sub-options depends on the chosen class. The sub-options supported by the default classes are:</p><table><tr><th>option </th><th>supported compaction strategy </th><th>default </th><th>description </th></tr><tr><td><code>enabled</code> </td><td><em>all</em> </td><td>true </td><td>A boolean denoting whether compaction should be enabled or not.</td></tr><tr><td><code>tombstone_threshold</code> </td><td><em>all</em> </td><td>0.2 </td><td>A ratio such that if a sstable has more than this ratio of gcable tombstones over all contained columns, the sstable will be compacted (with no other sstables) for the purpose of purging those tombstones. </td></tr><tr><td><code>tombstone_compaction_interval</code> </td><td><em>all</em>
</td><td>1 day </td><td>The minimum time to wait after an sstable creation time before considering it for “tombstone compaction”, where “tombstone compaction” is the compaction triggered if the sstable has more gcable tombstones than <code>tombstone_threshold</code>. </td></tr><tr><td><code>unchecked_tombstone_compaction</code> </td><td><em>all</em> </td><td>false </td><td>Setting this to true enables more aggressive tombstone compactions – single sstable tombstone compactions will run without checking how likely it is that they will be successful. </td></tr><tr><td><code>min_sstable_size</code> </td><td>SizeTieredCompactionStrategy </td><td>50MB </td><td>The size tiered strategy groups SSTables to compact in buckets. A bucket groups SSTables that differs from less than 50% in size. However, for small sizes, this would result in a bucketing that is too fine grained. <code
>min_sstable_size</code> defines a size threshold (in bytes) below which all SSTables belong to one unique bucket</td></tr><tr><td><code>min_threshold</code> </td><td>SizeTieredCompactionStrategy </td><td>4 </td><td>Minimum number of SSTables needed to start a minor compaction.</td></tr><tr><td><code>max_threshold</code> </td><td>SizeTieredCompactionStrategy </td><td>32 </td><td>Maximum number of SSTables processed by one minor compaction.</td></tr><tr><td><code>bucket_low</code> </td><td>SizeTieredCompactionStrategy </td><td>0.5 </td><td>Size tiered consider sstables to be within the same bucket if their size is within [average_size * <code>bucket_low</code>, average_size * <code>bucket_high</code> ] (i.e the default groups sstable whose sizes diverges by at most 50%)</td></tr><tr><td><code>bucket_high</code> </td><td>SizeTieredCompactionStrategy </td><td>1.5 </td><td>Siz
e tiered consider sstables to be within the same bucket if their size is within [average_size * <code>bucket_low</code>, average_size * <code>bucket_high</code> ] (i.e the default groups sstable whose sizes diverges by at most 50%).</td></tr><tr><td><code>sstable_size_in_mb</code> </td><td>LeveledCompactionStrategy </td><td>5MB </td><td>The target size (in MB) for sstables in the leveled strategy. Note that while sstable sizes should stay less or equal to <code>sstable_size_in_mb</code>, it is possible to exceptionally have a larger sstable as during compaction, data for a given partition key are never split into 2 sstables</td></tr></table><p>For the <code>compression</code> property, the following default sub-options are available:</p><table><tr><th>option </th><th>default </th><th>description </th></tr><tr><td><code>sstable_compression</code> </td><td>LZ4Compressor </td><td>The compression algorithm to use. Default compressor are: LZ
4Compressor, SnappyCompressor and DeflateCompressor. Use an empty string (<code>''</code>) to disable compression. Custom compressor can be provided by specifying the full class name as a <a href="#constants">string constant</a>.</td></tr><tr><td><code>chunk_length_kb</code> </td><td>64KB </td><td>On disk SSTables are compressed by block (to allow random reads). This defines the size (in KB) of said block. Bigger values may improve the compression rate, but increases the minimum size of data to be read from disk for a read </td></tr><tr><td><code>crc_check_chance</code> </td><td>1.0 </td><td>When compression is enabled, each compressed block includes a checksum of that block for the purpose of detecting disk bitrot and avoiding the propagation of corruption to other replica. This option defines the probability with which those checksums are checked during read. By default they are always checked. Set to 0 to disable checksum checking and to 0.5 for in
stance to check them every other read</td></tr></table><h4 id="Otherconsiderations">Other considerations:</h4><ul><li>When <a href="#insertStmt/"updating":#updateStmt">inserting</a> a given row, not all columns needs to be defined (except for those part of the key), and missing columns occupy no space on disk. Furthermore, adding new columns (see <a href=#alterStmt><tt>ALTER TABLE</tt></a>) is a constant time operation. There is thus no need to try to anticipate future usage (or to cry when you haven’t) when creating a table.</li></ul><h3 id="alterTableStmt">ALTER TABLE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><alter-table-stmt> ::= ALTER (TABLE | COLUMNFAMILY) <tablename> <instruction>
+
+<instruction> ::= ALTER <identifier> TYPE <type>
+ | ADD <identifier> <type>
+ | DROP <identifier>
+ | WITH <option> ( AND <option> )*
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>ALTER TABLE addamsFamily
+ALTER lastKnownLocation TYPE uuid;
+
+ALTER TABLE addamsFamily
+ADD gravesite varchar;
+
+ALTER TABLE addamsFamily
+WITH comment = 'A most excellent and useful column family'
+ AND read_repair_chance = 0.2;
+</pre></pre><p><br/>The <code>ALTER</code> statement is used to manipulate table definitions. It allows for adding new columns, dropping existing ones, changing the type of existing columns, or updating the table options. As with table creation, <code>ALTER COLUMNFAMILY</code> is allowed as an alias for <code>ALTER TABLE</code>.</p><p>The <code><tablename></code> is the table name optionally preceded by the keyspace name. The <code><instruction></code> defines the alteration to perform:</p><ul><li><code>ALTER</code>: Update the type of a given defined column. Note that the type of the <a href="#createTablepartitionClustering">clustering columns</a> cannot be modified as it induces the on-disk ordering of rows. Columns on which a <a href="#createIndexStmt">secondary index</a> is defined have the same restriction. Other columns are free from those restrictions (no validation of existing data is performed), but it is usually a bad idea to change the type to a non-compatible one,
unless no data have been inserted for that column yet, as this could confuse CQL drivers/tools.</li><li><code>ADD</code>: Adds a new column to the table. The <code><identifier></code> for the new column must not conflict with an existing column. Moreover, columns cannot be added to tables defined with the <code>COMPACT STORAGE</code> option.</li><li><code>DROP</code>: Removes a column from the table. Dropped columns will immediately become unavailable in the queries and will not be included in compacted sstables in the future. If a column is readded, queries won’t return values written before the column was last dropped. It is assumed that timestamps represent actual time, so if this is not your case, you should NOT readd previously dropped columns. Columns can’t be dropped from tables defined with the <code>COMPACT STORAGE</code> option.</li><li><code>WITH</code>: Allows to update the options of the table. The <a href="#createTableOptions">supported <code><option
></code></a> (and syntax) are the same as for the <code>CREATE TABLE</code> statement except that <code>COMPACT STORAGE</code> is not supported. Note that setting any <code>compaction</code> sub-options has the effect of erasing all previous <code>compaction</code> options, so you need to re-specify all the sub-options if you want to keep them. The same note applies to the set of <code>compression</code> sub-options.</li></ul><h3 id="dropTableStmt">DROP TABLE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><drop-table-stmt> ::= DROP TABLE ( IF EXISTS )? <tablename>
+</pre></pre><p><i>Sample:</i></p><pre class="sample"><pre>DROP TABLE worldSeriesAttendees;
+</pre></pre><p>The <code>DROP TABLE</code> statement results in the immediate, irreversible removal of a table, including all data contained in it. As for table creation, <code>DROP COLUMNFAMILY</code> is allowed as an alias for <code>DROP TABLE</code>.</p><p>If the table does not exist, the statement will return an error, unless <code>IF EXISTS</code> is used in which case the operation is a no-op.</p><h3 id="truncateStmt">TRUNCATE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><truncate-stmt> ::= TRUNCATE <tablename>
+</pre></pre><p><i>Sample:</i></p><pre class="sample"><pre>TRUNCATE superImportantData;
+</pre></pre><p>The <code>TRUNCATE</code> statement permanently removes all data from a table.</p><h3 id="createIndexStmt">CREATE INDEX</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><create-index-stmt> ::= CREATE ( CUSTOM )? INDEX ( IF NOT EXISTS )? ( <indexname> )?
+ ON <tablename> '(' <index-identifier> ')'
+ ( USING <string> ( WITH OPTIONS = <map-literal> )? )?
+
+<index-identifier> ::= <identifier>
+ | keys( <identifier> )
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>CREATE INDEX userIndex ON NerdMovies (user);
+CREATE INDEX ON Mutants (abilityId);
+CREATE INDEX ON users (keys(favs));
+CREATE CUSTOM INDEX ON users (email) USING 'path.to.the.IndexClass';
+CREATE CUSTOM INDEX ON users (email) USING 'path.to.the.IndexClass' WITH OPTIONS = {'storage': '/mnt/ssd/indexes/'};
+</pre></pre><p>The <code>CREATE INDEX</code> statement is used to create a new (automatic) secondary index for a given (existing) column in a given table. A name for the index itself can be specified before the <code>ON</code> keyword, if desired. If data already exists for the column, it will be indexed asynchronously. After the index is created, new data for the column is indexed automatically at insertion time.</p><p>Attempting to create an already existing index will return an error unless the <code>IF NOT EXISTS</code> option is used. If it is used, the statement will be a no-op if the index already exists.</p><h4 id="keysIndex">Indexes on Map Keys</h4><p>When creating an index on a <a href="#map">map column</a>, you may index either the keys or the values. If the column identifier is placed within the <code>keys()</code> function, the index will be on the map keys, allowing you to use <code>CONTAINS KEY</code> in <code>WHERE</code> clauses. Otherwise, the index will be on th
e map values.</p><h3 id="dropIndexStmt">DROP INDEX</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><drop-index-stmt> ::= DROP INDEX ( IF EXISTS )? ( <keyspace> '.' )? <identifier>
+</pre></pre><p><i>Sample:</i></p><pre class="sample"><pre>DROP INDEX userIndex;
+
+DROP INDEX userkeyspace.address_index;
+</pre></pre><p><br/>The <code>DROP INDEX</code> statement is used to drop an existing secondary index. The argument of the statement is the index name, which may optionally specify the keyspace of the index.</p><p>If the index does not exists, the statement will return an error, unless <code>IF EXISTS</code> is used in which case the operation is a no-op.</p><h3 id="createTypeStmt">CREATE TYPE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><create-type-stmt> ::= CREATE TYPE ( IF NOT EXISTS )? <typename>
+ '(' <field-definition> ( ',' <field-definition> )* ')'
+
+<typename> ::= ( <keyspace-name> '.' )? <identifier>
+
+<field-definition> ::= <identifier> <type>
+
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>CREATE TYPE address (
+ street_name text,
+ street_number int,
+ city text,
+ state text,
+ zip int
+)
+
+CREATE TYPE work_and_home_addresses (
+ home_address address,
+ work_address address
+)
+</pre></pre><p><br/>The <code>CREATE TYPE</code> statement creates a new user-defined type. Each type is a set of named, typed fields. Field types may be any valid type, including collections and other existing user-defined types.</p><p>Attempting to create an already existing type will result in an error unless the <code>IF NOT EXISTS</code> option is used. If it is used, the statement will be a no-op if the type already exists.</p><h4 id="createTypeName"><code><typename></code></h4><p>Valid type names are identifiers. The names of existing CQL types and <a href="#appendixB">reserved type names</a> may not be used.</p><p>If the type name is provided alone, the type is created with the current keyspace (see <a href="#useStmt"><tt>USE</tt></a>). If it is prefixed by an existing keyspace name, the type is created within the specified keyspace instead of the current keyspace.</p><h3 id="alterTypeStmt">ALTER TYPE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><alter-type-st
mt> ::= ALTER TYPE <typename> <instruction>
+
+<instruction> ::= ALTER <field-name> TYPE <type>
+ | ADD <field-name> <type>
+ | RENAME <field-name> TO <field-name> ( AND <field-name> TO <field-name> )*
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>ALTER TYPE address ALTER zip TYPE varint
+
+ALTER TYPE address ADD country text
+
+ALTER TYPE address RENAME zip TO zipcode AND street_name TO street
+</pre></pre><p><br/>The <code>ALTER TYPE</code> statement is used to manipulate type definitions. It allows for adding new fields, renaming existing fields, or changing the type of existing fields.</p><p>When altering the type of a column, the new type must be compatible with the previous type.</p><h3 id="dropTypeStmt">DROP TYPE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><drop-type-stmt> ::= DROP TYPE ( IF EXISTS )? <typename>
+</pre></pre><p><br/>The <code>DROP TYPE</code> statement results in the immediate, irreversible removal of a type. Attempting to drop a type that is still in use by another type or a table will result in an error.</p><p>If the type does not exist, an error will be returned unless <code>IF EXISTS</code> is used, in which case the operation is a no-op.</p><h3 id="createTriggerStmt">CREATE TRIGGER</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><create-trigger-stmt> ::= CREATE TRIGGER ( IF NOT EXISTS )? ( <triggername> )?
+ ON <tablename>
+ USING <string>
+
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>CREATE TRIGGER myTrigger ON myTable USING 'org.apache.cassandra.triggers.InvertedIndex';
+</pre></pre><p>The actual logic that makes up the trigger can be written in any Java (JVM) language and exists outside the database. You place the trigger code in a <code>lib/triggers</code> subdirectory of the Cassandra installation directory, it loads during cluster startup, and exists on every node that participates in a cluster. The trigger defined on a table fires before a requested DML statement occurs, which ensures the atomicity of the transaction.</p><h3 id="dropTriggerStmt">DROP TRIGGER</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><drop-trigger-stmt> ::= DROP TRIGGER ( IF EXISTS )? ( <triggername> )?
+ ON <tablename>
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>DROP TRIGGER myTrigger ON myTable;
+</pre></pre><p><code>DROP TRIGGER</code> statement removes the registration of a trigger created using <code>CREATE TRIGGER</code>.</p><h3 id="createFunctionStmt">CREATE FUNCTION</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><create-function-stmt> ::= CREATE ( OR REPLACE )?
+ FUNCTION ( IF NOT EXISTS )?
+ ( <keyspace> '.' )? <function-name>
+ '(' <arg-name> <arg-type> ( ',' <arg-name> <arg-type> )* ')'
+ ( CALLED | RETURNS NULL ) ON NULL INPUT
+ RETURNS <type>
+ LANGUAGE <language>
+ AS <body>
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>CREATE OR REPLACE FUNCTION somefunction
+ ( somearg int, anotherarg text, complexarg frozen<someUDT>, listarg list<bigint> )
+ RETURNS NULL ON NULL INPUT
+ RETURNS text
+ LANGUAGE java
+ AS $$
+ // some Java code
+ $$;
+CREATE FUNCTION akeyspace.fname IF NOT EXISTS
+ ( someArg int )
+ CALLED ON NULL INPUT
+ RETURNS text
+ LANGUAGE java
+ AS $$
+ // some Java code
+ $$;
+</pre></pre><p><code>CREATE FUNCTION</code> creates or replaces a user-defined function.</p><h4 id="functionSignature">Function Signature</h4><p>Signatures are used to distinguish individual functions. The signature consists of:</p><ol><li>The fully qualified function name – i.e <em>keyspace</em> plus <em>function-name</em></li><li>The concatenated list of all argument types</li></ol><p>Note that keyspace names, function names and argument types are subject to the default naming conventions and case-sensitivity rules.</p><p><code>CREATE FUNCTION</code> with the optional <code>OR REPLACE</code> keywords either creates a function or replaces an existing one with the same signature. A <code>CREATE FUNCTION</code> without <code>OR REPLACE</code> fails if a function with the same signature already exists.</p><p>Behavior on invocation with <code>null</code> values must be defined for each function. There are two options:</p><ol><li><code>RETURNS NULL ON NULL INPUT</code> declares th
at the function will always return <code>null</code> if any of the input arguments is <code>null</code>.</li><li><code>CALLED ON NULL INPUT</code> declares that the function will always be executed.</li></ol><p>If the optional <code>IF NOT EXISTS</code> keywords are used, the function will only be created if another function with the same signature does not exist.</p><p><code>OR REPLACE</code> and <code>IF NOT EXIST</code> cannot be used together.</p><p>Functions belong to a keyspace. If no keyspace is specified in <code><function-name></code>, the current keyspace is used (i.e. the keyspace specified using the <a href="#useStmt"><code>USE</code></a> statement). It is not possible to create a user-defined function in one of the system keyspaces.</p><p>See the section on <a href="#udfs">user-defined functions</a> for more information.</p><h3 id="dropFunctionStmt">DROP FUNCTION</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><drop-function-stmt> ::= DROP FUNCTION ( IF EXISTS )
?
+ ( <keyspace> '.' )? <function-name>
+ ( '(' <arg-type> ( ',' <arg-type> )* ')' )?
+
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>DROP FUNCTION myfunction;
+DROP FUNCTION mykeyspace.afunction;
+DROP FUNCTION afunction ( int );
+DROP FUNCTION afunction ( text );
+</pre></pre><p><code>DROP FUNCTION</code> statement removes a function created using <code>CREATE FUNCTION</code>.<br/>You must specify the argument types (<a href="#functionSignature">signature</a>) of the function to drop if there are multiple functions with the same name but a different signature (overloaded functions).</p><p><code>DROP FUNCTION</code> with the optional <code>IF EXISTS</code> keywords drops a function if it exists.</p><h3 id="createAggregateStmt">CREATE AGGREGATE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><create-aggregate-stmt> ::= CREATE ( OR REPLACE )?
+ AGGREGATE ( IF NOT EXISTS )?
+ ( <keyspace> '.' )? <aggregate-name>
+ '(' <arg-type> ( ',' <arg-type> )* ')'
+ SFUNC ( <keyspace> '.' )? <state-functionname>
+ STYPE <state-type>
+ ( FINALFUNC ( <keyspace> '.' )? <final-functionname> )?
+ ( INITCOND <init-cond> )?
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>CREATE AGGREGATE myaggregate ( val text )
+ SFUNC myaggregate_state
+ STYPE text
+ FINALFUNC myaggregate_final
+ INITCOND 'foo';
+</pre></pre><p>See the section on <a href="#udas">user-defined aggregates</a> for a complete example.</p><p><code>CREATE AGGREGATE</code> creates or replaces a user-defined aggregate.</p><p><code>CREATE AGGREGATE</code> with the optional <code>OR REPLACE</code> keywords either creates an aggregate or replaces an existing one with the same signature. A <code>CREATE AGGREGATE</code> without <code>OR REPLACE</code> fails if an aggregate with the same signature already exists.</p><p><code>CREATE AGGREGATE</code> with the optional <code>IF NOT EXISTS</code> keywords either creates an aggregate if it does not already exist.</p><p><code>OR REPLACE</code> and <code>IF NOT EXIST</code> cannot be used together.</p><p>Aggregates belong to a keyspace. If no keyspace is specified in <code><aggregate-name></code>, the current keyspace is used (i.e. the keyspace specified using the <a href="#useStmt"><code>USE</code></a> statement). It is not possible to create a user-defined aggregate in one o
f the system keyspaces.</p><p>Signatures for user-defined aggregates follow the <a href="#functionSignature">same rules</a> as for user-defined functions.</p><p><code>STYPE</code> defines the type of the state value and must be specified.</p><p>The optional <code>INITCOND</code> defines the initial state value for the aggregate. It defaults to <code>null</code>. A non-@null@ <code>INITCOND</code> must be specified for state functions that are declared with <code>RETURNS NULL ON NULL INPUT</code>.</p><p><code>SFUNC</code> references an existing function to be used as the state modifying function. The type of first argument of the state function must match <code>STYPE</code>. The remaining argument types of the state function must match the argument types of the aggregate function. State is not updated for state functions declared with <code>RETURNS NULL ON NULL INPUT</code> and called with <code>null</code>.</p><p>The optional <code>FINALFUNC</code> is called just before the aggregat
e result is returned. It must take only one argument with type <code>STYPE</code>. The return type of the <code>FINALFUNC</code> may be a different type. A final function declared with <code>RETURNS NULL ON NULL INPUT</code> means that the aggregate’s return value will be <code>null</code>, if the last state is <code>null</code>.</p><p>If no <code>FINALFUNC</code> is defined, the overall return type of the aggregate function is <code>STYPE</code>. If a <code>FINALFUNC</code> is defined, it is the return type of that function.</p><p>See the section on <a href="#udas">user-defined aggregates</a> for more information.</p><h3 id="dropAggregateStmt">DROP AGGREGATE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><drop-aggregate-stmt> ::= DROP AGGREGATE ( IF EXISTS )?
+ ( <keyspace> '.' )? <aggregate-name>
+ ( '(' <arg-type> ( ',' <arg-type> )* ')' )?
+</pre></pre><p></p><p><i>Sample:</i></p><pre class="sample"><pre>DROP AGGREGATE myAggregate;
+DROP AGGREGATE myKeyspace.anAggregate;
+DROP AGGREGATE someAggregate ( int );
+DROP AGGREGATE someAggregate ( text );
+</pre></pre><p>The <code>DROP AGGREGATE</code> statement removes an aggregate created using <code>CREATE AGGREGATE</code>. You must specify the argument types of the aggregate to drop if there are multiple aggregates with the same name but a different signature (overloaded aggregates).</p><p><code>DROP AGGREGATE</code> with the optional <code>IF EXISTS</code> keywords drops an aggregate if it exists, and does nothing if a function with the signature does not exist.</p><p>Signatures for user-defined aggregates follow the <a href="#functionSignature">same rules</a> as for user-defined functions.</p><h2 id="dataManipulation">Data Manipulation</h2><h3 id="insertStmt">INSERT</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><insertStatement> ::= INSERT INTO <tablename>
+ ( ( <name-list> VALUES <value-list> )
+ | ( JSON <string> ))
+ ( IF NOT EXISTS )?
+ ( USING <option> ( AND <option> )* )?
+
+<names-list> ::= '(' <identifier> ( ',' <identifier> )* ')'
+
+<value-list> ::= '(' <term-or-literal> ( ',' <term-or-literal> )* ')'
+
+<term-or-literal> ::= <term>
+ | <collection-literal>
+
+<option> ::= TIMESTAMP <integer>
+ | TTL <integer>
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>INSERT INTO NerdMovies (movie, director, main_actor, year)
+ VALUES ('Serenity', 'Joss Whedon', 'Nathan Fillion', 2005)
+USING TTL 86400;
+
+INSERT INTO NerdMovies JSON '{"movie": "Serenity", "director": "Joss Whedon", "year": 2005}'
+</pre></pre><p><br/>The <code>INSERT</code> statement writes one or more columns for a given row in a table. Note that since a row is identified by its <code>PRIMARY KEY</code>, at least the columns composing it must be specified. The list of columns to insert to must be supplied when using the <code>VALUES</code> syntax. When using the <code>JSON</code> syntax, they are optional. See the section on <a href="#insertJson"><code>INSERT JSON</code></a> for more details.</p><p>Note that unlike in SQL, <code>INSERT</code> does not check the prior existence of the row by default: the row is created if none existed before, and updated otherwise. Furthermore, there is no mean to know which of creation or update happened.</p><p>It is however possible to use the <code>IF NOT EXISTS</code> condition to only insert if the row does not exist prior to the insertion. But please note that using <code>IF NOT EXISTS</code> will incur a non negligible performance cost (internally, Paxos will be use
d) so this should be used sparingly.</p><p>All updates for an <code>INSERT</code> are applied atomically and in isolation.</p><p>Please refer to the <a href="#updateOptions"><code>UPDATE</code></a> section for information on the <code><option></code> available and to the <a href="#collections">collections</a> section for use of <code><collection-literal></code>. Also note that <code>INSERT</code> does not support counters, while <code>UPDATE</code> does.</p><h3 id="updateStmt">UPDATE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><update-stmt> ::= UPDATE <tablename>
+ ( USING <option> ( AND <option> )* )?
+ SET <assignment> ( ',' <assignment> )*
+ WHERE <where-clause>
+ ( IF <condition> ( AND condition )* )?
+
+<assignment> ::= <identifier> '=' <term>
+ | <identifier> '=' <identifier> ('+' | '-') (<int-term> | <set-literal> | <list-literal>)
+ | <identifier> '=' <identifier> '+' <map-literal>
+ | <identifier> '[' <term> ']' '=' <term>
+
+<condition> ::= <identifier> '=' <term>
+ | <identifier> '[' <term> ']' '=' <term>
+
+<where-clause> ::= <relation> ( AND <relation> )*
+
+<relation> ::= <identifier> '=' <term>
+ | <identifier> IN '(' ( <term> ( ',' <term> )* )? ')'
+ | <identifier> IN '?'
+
+<option> ::= TIMESTAMP <integer>
+ | TTL <integer>
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>UPDATE NerdMovies USING TTL 400
+SET director = 'Joss Whedon',
+ main_actor = 'Nathan Fillion',
+ year = 2005
+WHERE movie = 'Serenity';
+
+UPDATE UserActions SET total = total + 2 WHERE user = B70DE1D0-9908-4AE3-BE34-5573E5B09F14 AND action = 'click';
+</pre></pre><p><br/>The <code>UPDATE</code> statement writes one or more columns for a given row in a table. The <code><where-clause></code> is used to select the row to update and must include all columns composing the <code>PRIMARY KEY</code> (the <code>IN</code> relation is only supported for the last column of the partition key). Other columns values are specified through <code><assignment></code> after the <code>SET</code> keyword.</p><p>Note that unlike in SQL, <code>UPDATE</code> does not check the prior existence of the row by default: the row is created if none existed before, and updated otherwise. Furthermore, there is no mean to know which of creation or update happened.</p><p>It is however possible to use the conditions on some columns through <code>IF</code>, in which case the row will not be updated unless such condition are met. But please note that using <code>IF</code> conditions will incur a non negligible performance cost (internally, Paxos will be used) so
this should be used sparingly.</p><p>In an <code>UPDATE</code> statement, all updates within the same partition key are applied atomically and in isolation.</p><p>The <code>c = c + 3</code> form of <code><assignment></code> is used to increment/decrement counters. The identifier after the ‘=’ sign <strong>must</strong> be the same than the one before the ‘=’ sign (Only increment/decrement is supported on counters, not the assignment of a specific value).</p><p>The <code>id = id + <collection-literal></code> and <code>id[value1] = value2</code> forms of <code><assignment></code> are for collections. Please refer to the <a href="#collections">relevant section</a> for more details.</p><h4 id="updateOptions"><code><options></code></h4><p>The <code>UPDATE</code> and <code>INSERT</code> statements allows to specify the following options for the insertion:</p><ul><li><code>TIMESTAMP</code>: sets the timestamp for the operation. If not specified, the coo
rdinator will use the current time (in microseconds) at the start of statement execution as the timestamp. This is usually a suitable default.</li><li><code>TTL</code>: allows to specify an optional Time To Live (in seconds) for the inserted values. If set, the inserted values are automatically removed from the database after the specified time. Note that the TTL concerns the inserted values, not the column themselves. This means that any subsequent update of the column will also reset the TTL (to whatever TTL is specified in that update). By default, values never expire. A TTL of 0 or a negative one is equivalent to no TTL.</li></ul><h3 id="deleteStmt">DELETE</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><delete-stmt> ::= DELETE ( <selection> ( ',' <selection> )* )?
+ FROM <tablename>
+ ( USING TIMESTAMP <integer>)?
+ WHERE <where-clause>
+ ( IF ( EXISTS | ( <condition> ( AND <condition> )*) ) )?
+
+<selection> ::= <identifier> ( '[' <term> ']' )?
+
+<where-clause> ::= <relation> ( AND <relation> )*
+
+<relation> ::= <identifier> '=' <term>
+ | <identifier> IN '(' ( <term> ( ',' <term> )* )? ')'
+ | <identifier> IN '?'
+
+<condition> ::= <identifier> '=' <term>
+ | <identifier> '[' <term> ']' '=' <term>
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>DELETE FROM NerdMovies USING TIMESTAMP 1240003134 WHERE movie = 'Serenity';
+
+DELETE phone FROM Users WHERE userid IN (C73DE1D3-AF08-40F3-B124-3FF3E5109F22, B70DE1D0-9908-4AE3-BE34-5573E5B09F14);
+</pre></pre><p><br/>The <code>DELETE</code> statement deletes columns and rows. If column names are provided directly after the <code>DELETE</code> keyword, only those columns are deleted from the row indicated by the <code><where-clause></code> (the <code>id[value]</code> syntax in <code><selection></code> is for collection, please refer to the <a href="#collections">collection section</a> for more details). Otherwise whole rows are removed. The <code><where-clause></code> allows to specify the key for the row(s) to delete (the <code>IN</code> relation is only supported for the last column of the partition key).</p><p><code>DELETE</code> supports the <code>TIMESTAMP</code> options with the same semantic that in the <a href="#updateStmt"><code>UPDATE</code></a> statement.</p><p>In a <code>DELETE</code> statement, all deletions within the same partition key are applied atomically and in isolation.</p><p>A <code>DELETE</code> operation application can be conditioned using <c
ode>IF</code> like for <code>UPDATE</code> and <code>INSERT</code>. But please not that as for the later, this will incur a non negligible performance cost (internally, Paxos will be used) and so should be used sparingly.</p><h3 id="batchStmt">BATCH</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><batch-stmt> ::= BEGIN ( UNLOGGED | COUNTER ) BATCH
+ ( USING <option> ( AND <option> )* )?
+ <modification-stmt> ( ';' <modification-stmt> )*
+ APPLY BATCH
+
+<modification-stmt> ::= <insert-stmt>
+ | <update-stmt>
+ | <delete-stmt>
+
+<option> ::= TIMESTAMP <integer>
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>BEGIN BATCH
+ INSERT INTO users (userid, password, name) VALUES ('user2', 'ch@ngem3b', 'second user');
+ UPDATE users SET password = 'ps22dhds' WHERE userid = 'user3';
+ INSERT INTO users (userid, password) VALUES ('user4', 'ch@ngem3c');
+ DELETE name FROM users WHERE userid = 'user1';
+APPLY BATCH;
+</pre></pre><p>The <code>BATCH</code> statement group multiple modification statements (insertions/updates and deletions) into a single statement. It serves several purposes:</p><ol><li>It saves network round-trips between the client and the server (and sometimes between the server coordinator and the replicas) when batching multiple updates.</li><li>All updates in a <code>BATCH</code> belonging to a given partition key are performed in isolation.</li><li>By default, all operations in the batch are performed atomically. See the notes on <a href="#unloggedBatch"><code>UNLOGGED</code></a> for more details.</li></ol><p>Note that:</p><ul><li><code>BATCH</code> statements may only contain <code>UPDATE</code>, <code>INSERT</code> and <code>DELETE</code> statements.</li><li>Batches are <em>not</em> a full analogue for SQL transactions.</li><li>If a timestamp is not specified for each operation, then all operations will be applied with the same timestamp. Due to Cassandra’s conflict
resolution procedure in the case of <a href="http://wiki.apache.org/cassandra/FAQ#clocktie">timestamp ties</a>, operations may be applied in an order that is different from the order they are listed in the <code>BATCH</code> statement. To force a particular operation ordering, you must specify per-operation timestamps.</li></ul><h4 id="unloggedBatch"><code>UNLOGGED</code></h4><p>By default, Cassandra uses a batch log to ensure all operations in a batch are applied atomically. (Note that the operations are still only isolated within a single partition.)</p><p>There is a performance penalty for batch atomicity when a batch spans multiple partitions. If you do not want to incur this penalty, you can tell Cassandra to skip the batchlog with the <code>UNLOGGED</code> option. If the <code>UNLOGGED</code> option is used, operations are only atomic within a single partition.</p><h4 id="counterBatch"><code>COUNTER</code></h4><p>Use the <code>COUNTER</code> option for batched counter updates.
Unlike other updates in Cassandra, counter updates are not idempotent.</p><h4 id="batchOptions"><code><option></code></h4><p><code>BATCH</code> supports both the <code>TIMESTAMP</code> option, with similar semantic to the one described in the <a href="#updateOptions"><code>UPDATE</code></a> statement (the timestamp applies to all the statement inside the batch). However, if used, <code>TIMESTAMP</code> <strong>must not</strong> be used in the statements within the batch.</p><h2 id="queries">Queries</h2><h3 id="selectStmt">SELECT</h3><p><i>Syntax:</i></p><pre class="syntax"><pre><select-stmt> ::= SELECT ( JSON )? <select-clause>
+ FROM <tablename>
+ ( WHERE <where-clause> )?
+ ( ORDER BY <order-by> )?
+ ( LIMIT <integer> )?
+ ( ALLOW FILTERING )?
+
+<select-clause> ::= DISTINCT? <selection-list>
+ | COUNT '(' ( '*' | '1' ) ')' (AS <identifier>)?
+
+<selection-list> ::= <selector> (AS <identifier>)? ( ',' <selector> (AS <identifier>)? )*
+ | '*'
+
+<selector> ::= <identifier>
+ | WRITETIME '(' <identifier> ')'
+ | TTL '(' <identifier> ')'
+ | <function> '(' (<selector> (',' <selector>)*)? ')'
+
+<where-clause> ::= <relation> ( AND <relation> )*
+
+<relation> ::= <identifier> <op> <term>
+ | '(' <identifier> (',' <identifier>)* ')' <op> <term-tuple>
+ | <identifier> IN '(' ( <term> ( ',' <term>)* )? ')'
+ | '(' <identifier> (',' <identifier>)* ')' IN '(' ( <term-tuple> ( ',' <term-tuple>)* )? ')'
+ | TOKEN '(' <identifier> ( ',' <identifer>)* ')' <op> <term>
+
+<op> ::= '=' | '<' | '>' | '<=' | '>=' | CONTAINS | CONTAINS KEY
+<order-by> ::= <ordering> ( ',' <odering> )*
+<ordering> ::= <identifer> ( ASC | DESC )?
+<term-tuple> ::= '(' <term> (',' <term>)* ')'
+</pre></pre><p><br/><i>Sample:</i></p><pre class="sample"><pre>SELECT name, occupation FROM users WHERE userid IN (199, 200, 207);
+
+SELECT JSON name, occupation FROM users WHERE userid = 199;
+
+SELECT name AS user_name, occupation AS user_occupation FROM users;
+
+SELECT time, value
+FROM events
+WHERE event_type = 'myEvent'
+ AND time > '2011-02-03'
+ AND time <= '2012-01-01'
+
+SELECT COUNT(*) FROM users;
+
+SELECT COUNT(*) AS user_count FROM users;
+
+</pre></pre><p><br/>The <code>SELECT</code> statements reads one or more columns for one or more rows in a table. It returns a result-set of rows, where each row contains the collection of columns corresponding to the query. If the <code>JSON</code> keyword is used, the results for each row will contain only a single column named “json”. See the section on <a href="#selectJson"><code>SELECT JSON</code></a> for more details.</p><h4 id="selectSelection"><code><select-clause></code></h4><p>The <code><select-clause></code> determines which columns needs to be queried and returned in the result-set. It consists of either the comma-separated list of <selector> or the wildcard character (<code>*</code>) to select all the columns defined for the table.</p><p>A <code><selector></code> is either a column name to retrieve or a <code><function></code> of one or more @<term>@s. The function allowed are the same as for <code><term></code> and are described in the <a h
ref="#functions">function section</a>. In addition to these generic functions, the <code>WRITETIME</code> (resp. <code>TTL</code>) function allows to select the timestamp of when the column was inserted (resp. the time to live (in seconds) for the column (or null if the column has no expiration set)).</p><p>Any <code><selector></code> can be aliased using <code>AS</code> keyword (see examples). Please note that <code><where-clause></code> and <code><order-by></code> clause should refer to the columns by their original names and not by their aliases.</p><p>The <code>COUNT</code> keyword can be used with parenthesis enclosing <code>*</code>. If so, the query will return a single result: the number of rows matching the query. Note that <code>COUNT(1)</code> is supported as an alias.</p><h4 id="selectWhere"><code><where-clause></code></h4><p>The <code><where-clause></code> specifies which rows must be queried. It is composed of relations on the columns that are part of th
e <code>PRIMARY KEY</code> and/or have a <a href="#createIndexStmt">secondary index</a> defined on them.</p><p>Not all relations are allowed in a query. For instance, non-equal relations (where <code>IN</code> is considered as an equal relation) on a partition key are not supported (but see the use of the <code>TOKEN</code> method below to do non-equal queries on the partition key). Moreover, for a given partition key, the clustering columns induce an ordering of rows and relations on them is restricted to the relations that allow to select a <strong>contiguous</strong> (for the ordering) set of rows. For instance, given</p><pre class="sample"><pre>CREATE TABLE posts (
+ userid text,
+ blog_title text,
+ posted_at timestamp,
+ entry_title text,
+ content text,
+ category int,
+ PRIMARY KEY (userid, blog_title, posted_at)
+)
+</pre></pre><p>The following query is allowed:</p><pre class="sample"><pre>SELECT entry_title, content FROM posts WHERE userid='john doe' AND blog_title='John''s Blog' AND posted_at >= '2012-01-01' AND posted_at < '2012-01-31'
+</pre></pre><p>But the following one is not, as it does not select a contiguous set of rows (and we suppose no secondary indexes are set):</p><pre class="sample"><pre>// Needs a blog_title to be set to select ranges of posted_at
+SELECT entry_title, content FROM posts WHERE userid='john doe' AND posted_at >= '2012-01-01' AND posted_at < '2012-01-31'
+</pre></pre><p>When specifying relations, the <code>TOKEN</code> function can be used on the <code>PARTITION KEY</code> column to query. In that case, rows will be selected based on the token of their <code>PARTITION_KEY</code> rather than on the value. Note that the token of a key depends on the partitioner in use, and that in particular the RandomPartitioner won’t yield a meaningful order. Also note that ordering partitioners always order token values by bytes (so even if the partition key is of type int, <code>token(-1) > token(0)</code> in particular). Example:</p><pre class="sample"><pre>SELECT * FROM posts WHERE token(userid) > token('tom') AND token(userid) < token('bob')
+</pre></pre><p>Moreover, the <code>IN</code> relation is only allowed on the last column of the partition key and on the last column of the full primary key.</p><p>It is also possible to “group” <code>CLUSTERING COLUMNS</code> together in a relation using the tuple notation. For instance:</p><pre class="sample"><pre>SELECT * FROM posts WHERE userid='john doe' AND (blog_title, posted_at) > ('John''s Blog', '2012-01-01')
+</pre></pre><p>will request all rows that sorts after the one having “John's Blog” as <code>blog_tile</code> and ‘2012-01-01’ for <code>posted_at</code> in the clustering order. In particular, rows having a <code>post_at <= '2012-01-01'</code> will be returned as long as their <code>blog_title > 'John''s Blog'</code>, which wouldn’t be the case for:</p><pre class="sample"><pre>SELECT * FROM posts WHERE userid='john doe' AND blog_title > 'John''s Blog' AND posted_at > '2012-01-01'
+</pre></pre><p>The tuple notation may also be used for <code>IN</code> clauses on <code>CLUSTERING COLUMNS</code>:</p><pre class="sample"><pre>SELECT * FROM posts WHERE userid='john doe' AND (blog_title, posted_at) IN (('John''s Blog', '2012-01-01), ('Extreme Chess', '2014-06-01'))
+</pre></pre><p>The <code>CONTAINS</code> operator may only be used on collection columns (lists, sets, and maps). In the case of maps, <code>CONTAINS</code> applies to the map values. The <code>CONTAINS KEY</code> operator may only be used on map columns and applies to the map keys.</p><h4 id="selectOrderBy"><code><order-by></code></h4><p>The <code>ORDER BY</code> option allows to select the order of the returned results. It takes as argument a list of column names along with the order for the column (<code>ASC</code> for ascendant and <code>DESC</code> for descendant, omitting the order being equivalent to <code>ASC</code>). Currently the possible orderings are limited (which depends on the table <a href="#createTableOptions"><code>CLUSTERING ORDER</code></a>):</p><ul><li>if the table has been defined without any specific <code>CLUSTERING ORDER</code>, then then allowed orderings are the order induced by the clustering columns and the reverse of that one.</li><li>otherwise, the
orderings allowed are the order of the <code>CLUSTERING ORDER</code> option and the reversed one.</li></ul><h4 id="selectLimit"><code>LIMIT</code></h4><p>The <code>LIMIT</code> option to a <code>SELECT</code> statement limits the number of rows returned by a query.</p><h4 id="selectAllowFiltering"><code>ALLOW FILTERING</code></h4><p>By default, CQL only allows select queries that don’t involve “filtering” server side, i.e. queries where we know that all (live) record read will be returned (maybe partly) in the result set. The reasoning is that those “non filtering” queries have predictable performance in the sense that they will execute in a time that is proportional to the amount of data <strong>returned</strong> by the query (which can be controlled through <code>LIMIT</code>).</p><p>The <code>ALLOW FILTERING</code> option allows to explicitly allow (some) queries that require filtering. Please note that a query using <code>ALLOW FILTERING</code> may
thus have unpredictable performance (for the definition above), i.e. even a query that selects a handful of records <strong>may</strong> exhibit performance that depends on the total amount of data stored in the cluster.</p><p>For instance, considering the following table holding user profiles with their year of birth (with a secondary index on it) and country of residence:</p><pre class="sample"><pre>CREATE TABLE users (
+ username text PRIMARY KEY,
+ firstname text,
+ lastname text,
+ birth_year int,
+ country text
+)
+
+CREATE INDEX ON users(birth_year);
+</pre></pre><p></p><p>Then the following queries are valid:</p><pre class="sample"><pre>SELECT * FROM users;
+SELECT firstname, lastname FROM users WHERE birth_year = 1981;
+</pre></pre><p>because in both case, Cassandra guarantees that these queries performance will be proportional to the amount of data returned. In particular, if no users are born in 1981, then the second query performance will not depend of the number of user profile stored in the database (not directly at least: due to secondary index implementation consideration, this query may still depend on the number of node in the cluster, which indirectly depends on the amount of data stored. Nevertheless, the number of nodes will always be multiple number of magnitude lower than the number of user profile stored). Of course, both query may return very large result set in practice, but the amount of data returned can always be controlled by adding a <code>LIMIT</code>.</p><p>However, the following query will be rejected:</p><pre class="sample"><pre>SELECT firstname, lastname FROM users WHERE birth_year = 1981 AND country = 'FR';
+</pre></pre><p>because Cassandra cannot guarantee that it won’t have to scan large amount of data even if the result to those query is small. Typically, it will scan all the index entries for users born in 1981 even if only a handful are actually from France. However, if you “know what you are doing”, you can force the execution of this query by using <code>ALLOW FILTERING</code> and so the following query is valid:</p><pre class="sample"><pre>SELECT firstname, lastname FROM users WHERE birth_year = 1981 AND country = 'FR' ALLOW FILTERING;
+</pre></pre><h2 id="types">Data Types</h2><p>CQL supports a rich set of data types for columns defined in a table, including collection types. On top of those native and collection types, users can also provide custom types (through a JAVA class extending <code>AbstractType</code> loadable by Cassandra). The syntax of types is thus:</p><pre class="syntax"><pre><type> ::= <native-type>
+ | <collection-type>
+ | <tuple-type>
+ | <string> // Used for custom types. The fully-qualified name of a JAVA class
+
+<native-type> ::= ascii
+ | bigint
+ | blob
+ | boolean
+ | counter
+ | date
+ | decimal
+ | double
+ | float
+ | inet
+ | int
+ | text
+ | time
+ | timestamp
+ | timeuuid
+ | uuid
+ | varchar
+ | varint
+
+<collection-type> ::= list '<' <native-type> '>'
+ | set '<' <native-type> '>'
+ | map '<' <native-type> ',' <native-type> '>'
+<tuple-type> ::= tuple '<' <type> (',' <type>)* '>'
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