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Create hooks to let a loadable plugin monitor (or even replace) the planner

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and/or create plans for hypothetical situations; in particular, investigate
plans that would be generated using hypothetical indexes.  This is a
heavily-rewritten version of the hooks proposed by Gurjeet Singh for his
Index Advisor project.  In this formulation, the index advisor can be
entirely a loadable module instead of requiring a significant part to be
in the core backend, and plans can be generated for hypothetical indexes
without requiring the creation and rolling-back of system catalog entries.

The index advisor patch as-submitted is not compatible with these hooks,
but it needs significant work anyway due to other 8.2-to-8.3 planner
changes.  With these hooks in the core backend, development of the advisor
can proceed as a pgfoundry project.
This commit is contained in:
Tom Lane
2007-05-25 17:54:25 +00:00
parent ce5b24abed
commit 604ffd280b
9 changed files with 168 additions and 62 deletions
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21
src/backend/commands/prepare.c
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@ -10,7 +10,7 @@
* Copyright (c) 2002-2007, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.75 2007/04/27 22:05:47 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.76 2007/05/25 17:54:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -678,8 +678,6 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, ExplainStmt *stmt,
if (IsA(pstmt, PlannedStmt))
{
QueryDesc *qdesc;
if (execstmt->into)
{
if (pstmt->commandType != CMD_SELECT ||
@ -694,22 +692,7 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, ExplainStmt *stmt,
pstmt->intoClause = execstmt->into;
}
/*
* Update snapshot command ID to ensure this query sees results of
* any previously executed queries. (It's a bit cheesy to modify
* ActiveSnapshot without making a copy, but for the limited ways
* in which EXPLAIN can be invoked, I think it's OK, because the
* active snapshot shouldn't be shared with anything else anyway.)
*/
ActiveSnapshot->curcid = GetCurrentCommandId();
/* Create a QueryDesc requesting no output */
qdesc = CreateQueryDesc(pstmt,
ActiveSnapshot, InvalidSnapshot,
None_Receiver,
paramLI, stmt->analyze);
ExplainOnePlan(qdesc, stmt, tstate);
ExplainOnePlan(pstmt, paramLI, stmt, tstate);
}
else
{