[CALCITE-1472] Support CROSS/OUTER APPLY syntax

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.11.0
• Assignee: Julian Hyde
• Reporter: Jark Wu
• Created: 27/Oct/16 07:28
• Updated: 06/Jan/17 19:30
• Resolved: 29/Nov/16 20:50

Description

The CROSS/OUTER APPLY is very similar to CROSS JOIN and OUTER JOIN. The difference is that the APPLY operator is used to invoke a table-valued function. This is not a standard SQL syntax , but introduced from MS SQL Server [1].

The APPLY operator can be expressed by Calcite’s LATERAL TABLE . That means the

SELECT MyTable.*, t.s FROM MyTable CROSS APPLY split(MyTable.a)) AS t(s)

corresponds to :

SELECT MyTable.*, t.s FROM MyTable, LATERAL TABLE(split(MyTable.a)) AS t(s)

and

SELECT MyTable.*, t.s FROM MyTable OUTER APPLY split(MyTable.a)) AS t(s)

corresponds to:

SELECT MyTable.*, t.s FROM MyTable LEFT JOIN LATERAL TABLE(split(MyTable.a)) AS t(s) ON TRUE

The ON TRUE part is necessary for LEFT JOIN, but it's trivial for users. That's why I'm introducing "CROSS/OUTER APPLY" which will simplify the SQL a lot.

As the APPLY can be expressed by LATERAL, so the only thing we need to touch is the Parser (see [2] and search FLINK to find the modification).

[1] https://technet.microsoft.com/en-us/library/ms175156(v=sql.105).aspx
[2] https://github.com/wuchong/flink/blob/60812e51156ec9fa6088154d2f6dea8c1ff9ac17/flink-libraries/flink-table/src/main/codegen/templates/Parser.jj

Issue Links

• is related to: CALCITE-1490 Allow table functions without explicit TABLE
• links to: PR 325