[jira] [Commented] (CASSANDRA-7062) Extension of static columns for compound cluster keys

["DOAN DuyHai (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-7062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14936709#comment-14936709 ] 

DOAN DuyHai commented on CASSANDRA-7062:
----------------------------------------

Now that [CASSANDRA-8099] is done, can we look again into this JIRA ?

I have a very relevant use-case for a customer. They want to store store an hierarchy of data for user expenses:

{code:sql}
CREATE TABLE user_expenses(
 user_id bigint,
 firstname text static,
 lastname text static,
 report_id uuid,
 report_title text,
 report_amount double,
 report_xxx ....
 ...,
 line_id uuid,
 line_item text,
 line-amount double,
 ...
 PRIMARY KEY((user_id), report_id, line_id)
)
{code}

So basically we have 2 levels of nesting:
 1 user - N reports
 1 report - N lines

 With the above data model,  all report data are *duplicated* for each line so that any update on report_title or other report property will require the *anti-pattern read-before-write*:

 1. Select all line_id for this report_id
 2. For each line_id, perform the update

One possible trick is to use a static map<report_id, report_property> but it's far from being elegant, not to say dirty.

So I believe that there is definitely a need for static columns that are *relative* to a clustering column. 


> Extension of static columns for compound cluster keys
> -----------------------------------------------------
>
>                 Key: CASSANDRA-7062
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7062
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Constance Eustace
>
> CASSANDRA-6561 implemented static columns for a given partition key.
> What this is proposing for a compound cluster key is a static column that is static at intermediate parts of a compound cluster key. This example shows a table modelling a moderately complex EAV pattern  :
> {code}
> CREATE TABLE t (
>    entityID text,
>    propertyName text,
>    valueIndex text,
>    entityName text static (entityID),
>    propertyType text static (entityID, propertyName),
>    propertyRelations List<text> static (entityID, propertyName),
>    data text,
>    PRIMARY KEY (entityID, (propertyName,valueIndex))
> )
> {code}
> So in this example has the following static columns:
> - the entityName column behaves exactly as CASSANDRA-6561 details, so all cluster rows have the same value
> - the propertyType and propertyRelations columns are static with respect to the remaining parts of the cluster key (that is, across all valueIndex values for a given propertyName), so an update to those values for an entityID and a propertyName will be shared/constant by all the value rows...
> Is this a relatively simple extension of the same mechanism in -6561, or is this a "whoa, you have no idea what you are proposing"?
> Sample data:
> Mary and Jane aren't married...
> {code}
> INSERT INTO t (entityID, entityName, propertyName, propertyType, valueIndex, data) VALUES ('0001','MARY MATALIN','married','SingleValue','0','false');
> INSERT INTO t (entityID, entityName, propertyName, propertyType, valueIndex, data) VALUES ('0002','JANE JOHNSON','married','SingleValue','0','false');
> INSERT INTO t (entityID, entityName, propertyName, propertyType, valueIndex) VALUES ('0001','MARY MATALIN','kids','NOVALUE','');
> INSERT INTO t (entityID, entityName, propertyName, propertyType, valueIndex) VALUES ('0002','JANE JOHNSON','kids','NOVALUE','');
> {code}
> {code}
> SELECT * FROM t:
> 0001 MARY MATALIN  married   SingleValue   0   false
> 0001 MARY MATALIN  kids         NOVALUE          null
> 0002 JANE JOHNSON  married   SingleValue   0   false
> 0002 JANE JOHNSON  kids         NOVALUE          null
> {code}
> Then mary and jane get married (so the entityName column that is static on the partition key is updated just like CASSANDRA-6561 )
> {code}
> INSERT INTO t (entityID, entityName, propertyName, propertyType, valueIndex, data) VALUES ('0001','MARY SMITH','married','SingleValue','0','TRUE');
> INSERT INTO t (entityID, entityName, propertyName, propertyType, valueIndex, data) VALUES ('0002','JANE JONES','married','SingleValue','0','TRUE');
> {code}
> {code}
> SELECT * FROM t:
> 0001 MARY SMITH  married   SingleValue   0   TRUE
> 0001 MARY SMITH  kids         NOVALUE          null
> 0002 JANE JONES   married   SingleValue   0   TRUE
> 0002 JANE JONES   kids         NOVALUE          null
> {code}
> Then mary and jane have a kid, so we add another value to the kids attribute:
> {code}
> INSERT INTO t (entityID, propertyName, propertyType, valueIndex,data) VALUES ('0001','kids','SingleValue','0','JIM-BOB');
> INSERT INTO t (entityID, propertyName, propertyType, valueIndex,data) VALUES ('0002','kids','SingleValue','0','JENNY');
> {code}
> {code}
> SELECT * FROM t:
> 0001 MARY SMITH  married   SingleValue   0   TRUE
> 0001 MARY SMITH  kids         SingleValue        null
> 0001 MARY SMITH  kids         SingleValue   0   JIM-BOB
> 0002 JANE JONES   married   SingleValue   0   TRUE
> 0002 JANE JONES   kids         SingleValue        null
> 0002 JANE JONES   kids         SingleValue   0   JENNY
> {code}
> Then Mary has ANOTHER kid, which demonstrates the partially static column relative to the cluster key, as ALL value rows for the property 'kids' get updated to the new value:
> {code}
> INSERT INTO t (entityID, propertyName, propertyType, valueIndex,data) VALUES ('0001','kids','MultiValue','1','HARRY');
> {code}
> {code}
> SELECT * FROM t:
> 0001 MARY SMITH  married   SingleValue  0   TRUE
> 0001 MARY SMITH  kids      MultiValue          null
> 0001 MARY SMITH  kids      MultiValue     0   JIM-BOB
> 0001 MARY SMITH  kids      MultiValue     1   HARRY
> 0002 JANE JONES  married   SingleValue   0   TRUE
> 0002 JANE JONES  kids      SingleValue        null
> 0002 JANE JONES  kids      SingleValue   0   JENNY
> {code}
> ... ok, hopefully that example isn't TOO complicated. Yes, there's a stupid hack bug in there with the null/empty row for the kids attribute, but please bear with me on that 
> Generally speaking, this will aid in flattening / denormalization of relational constructs into cassandra-friendly schemas. In the above example we are flattening a relational schema of three tables: entity, property, and value tables into a single sparse flattened denormalized compound table.



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