[jira] [Created] (COMDEV-468) Apache ShardingSphere: Solve unsupported Postgres sql about statements that start with 'd', 'e', 'f', 'i' for ShardingSphere Parser

["Chuxin Chen (Jira)" <ji...@apache.org>]

Chuxin Chen created COMDEV-468:
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             Summary: Apache ShardingSphere: Solve unsupported Postgres sql about statements that start with 'd', 'e', 'f', 'i' for ShardingSphere Parser
                 Key: COMDEV-468
                 URL: https://issues.apache.org/jira/browse/COMDEV-468
             Project: Community Development
          Issue Type: Improvement
          Components: GSoC/Mentoring ideas
            Reporter: Chuxin Chen


h2. Apache ShardingSphere

Apache ShardingSphere is positioned as a Database Plus, and aims at building a standard layer and ecosystem above heterogeneous databases. It focuses on how to reuse existing databases and their respective upper layer, rather than creating a new database. The goal is to minimize or eliminate the challenges caused by underlying databases fragmentation.

{*}Page{*}: [https://shardingsphere.apache.org|https://shardingsphere.apache.org/]
{*}Github{*}: [https://github.com/apache/shardingsphere] 
h2. Background

ShardingSphere parser engine helps users parse a SQL to get the AST (Abstract Syntax Tree) and visit this tree to get SQLStatement (Java Object). At present, this parser engine can handle SQLs for `MySQL`, `PostgreSQL`, `SQLServer`, `openGauss` and `Oracle`, which means we have to understand different database dialect SQLs.
 
{*}More details{*}:
[https://shardingsphere.apache.org/document/current/en/reference/sharding/parse/] 
h2. Task

This issue is to solve the unsupported postgres sql about alter in [this file|https://github.com/apache/shardingsphere/blob/master/shardingsphere-test/shardingsphere-parser-test/src/main/resources/sql/unsupported/unsupported.xml] . * CALL
 * DO

 * DROP FUNCTION

 * DROP INDEX

 * DROP INSTANCE RULE

 * DROP REWRITE RULE

 * EXECUTE

 * EXPLAIN

 * FETCH

 * FETCH ABSOLUTE

 * FETCH ALL

 * FETCH BACKWARD

 * FETCH FIRST

 * FETCH LAST

 * FETCH NEXT

 * FETCH PRIOR

 * FETCH RELATIVE

 * IMPORT FOREIGN SCHEMA

 
You can *learn more* [here|https://www.postgresql.org/docs/current/sql-commands.html]. *
You may need to try to get why it's not supported.(antlr4 grammar? or not implement visit method) You can use [antlr4 plugins|https://plugins.jetbrains.com/plugin/7358-antlr-v4] to help you to analyze. You may need to visit [an official doc|https://www.postgresql.org/docs/current/sql-commands.html] to check the grammar.
 * After you fix it, remember to add a new corresponding SQL case in [SQL Cases|https://github.com/apache/shardingsphere/tree/master/shardingsphere-test/shardingsphere-parser-test/src/main/resources/sql/supported] and expected parsed result in [Expected Statment XML|https://github.com/apache/shardingsphere/tree/master/shardingsphere-test/shardingsphere-parser-test/src/main/resources/case].

 * Run [SQLParserParameterizedTest|https://github.com/apache/shardingsphere/blob/master/shardingsphere-test/shardingsphere-parser-test/src/main/java/org/apache/shardingsphere/test/sql/parser/parameterized/engine/SQLParserParameterizedTest.java] and [UnsupportedSQLParserParameterizedTest|https://github.com/apache/shardingsphere/blob/master/shardingsphere-test/shardingsphere-parser-test/src/main/java/org/apache/shardingsphere/test/sql/parser/parameterized/engine/UnsupportedSQLParserParameterizedTest.java] to make sure no exceptions.

 
{*}Notice{*}, these issues can be a good example.
[support alter foreign table for pg/og|https://github.com/apache/shardingsphere/pull/14944]
[support alter materialized view for pg/og.|https://github.com/apache/shardingsphere/pull/15331]
h2. Relevant Skills

 
1. Master JAVA language
2. Have a basic understanding of Antlr g4 file
3. Be familiar with Postgres SQLs 
h2. Targets files

 
1. Postgres SQLs g4 file: [https://github.com/apache/shardingsphere/blob/master/shardingsphere-sql-parser/shardingsphere-sql-parser-dialect/shardingsphere-sql-parser-postgresql/src/main/antlr4/org/apache/shardingsphere/sql/parser/autogen/PostgreSQLStatement.g4]
h3. Mentor

Chuxin Chen, Committer of Apache ShardingSphere, tuichenchuxin@apache.org

Zhengqiang Duan, Committer of Apache ShardingSphere, duanzhengqiang@apache.org



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