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Posted to notifications@asterixdb.apache.org by "Dmitry Lychagin (JIRA)" <ji...@apache.org> on 2019/01/17 18:12:00 UTC
[jira] [Resolved] (ASTERIXDB-2511) Refactor LET and WHERE clauses
into a single clause list
[ https://issues.apache.org/jira/browse/ASTERIXDB-2511?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Dmitry Lychagin resolved ASTERIXDB-2511.
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Resolution: Fixed
> Refactor LET and WHERE clauses into a single clause list
> ---------------------------------------------------------
>
> Key: ASTERIXDB-2511
> URL: https://issues.apache.org/jira/browse/ASTERIXDB-2511
> Project: Apache AsterixDB
> Issue Type: Improvement
> Components: COMP - Compiler
> Reporter: Dmitry Lychagin
> Assignee: Dmitry Lychagin
> Priority: Minor
>
> Currently SelectBlock has a list of LET clauses followed by a single WHERE clause. Some expression tree rewriting rules (e.g. InlineColumnAliasVisitor) ** introduce LET clauses which can only be placed before the WHERE clause because of this design. This approach creates a problem when rewriting window expressions because they might need to be placed after the WHERE clause to maintain the correct semantics.
> The proposal is to consolidate LET/WHERE clauses into a single list in the SelectBlock, so LET clauses can be placed either before or after the WHERE clause. The SELECT statement syntax won't be changed at this point, so it'll continue to support only multiple LET clauses followed by a single WHERE clause.
> LET/HAVING clauses after GROUP BY clause will also be consolidated into a single list.
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