Horton

create_unique_path and GEQO

Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>

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From: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-03-22T10:13:56Z
Lists: pgsql-hackers 
Hi,
In create_unique_path() there's comment
    /*
     * We must ensure path struct and subsidiary data are allocated in main
     * planning context; otherwise GEQO memory management causes trouble.
     */
    oldcontext = MemoryContextSwitchTo(root->planner_cxt);

    pathnode = makeNode(UniquePath);

This means that when GEQO resets the memory context, the RelOptInfo
for which this path is created and may be set to cheapest_unique_path
goes away, the unique path lingers on in the planner context.
Shouldn't we instead allocate the path in the same context as the
RelOptInfo similar to mark_dummy_rel()?

-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company

Commits

  1. Make create_unique_path manage memory like mark_dummy_rel.

  2. Use parameterized paths to generate inner indexscans more flexibly.

  3. Ensure mark_dummy_rel doesn't create dangling pointers in RelOptInfos.

  4. Refactor planner's pathkeys data structure to create a separate, explicit

  5. IN clauses appearing at top level of WHERE can now be handled as joins.