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Refactor the executor's API to support data-modifying CTEs better.

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The originally committed patch for modifying CTEs didn't interact well
with EXPLAIN, as noted by myself, and also had corner-case problems with
triggers, as noted by Dean Rasheed.  Those problems show it is really not
practical for ExecutorEnd to call any user-defined code; so split the
cleanup duties out into a new function ExecutorFinish, which must be called
between the last ExecutorRun call and ExecutorEnd.  Some Asserts have been
added to these functions to help verify correct usage.

It is no longer necessary for callers of the executor to call
AfterTriggerBeginQuery/AfterTriggerEndQuery for themselves, as this is now
done by ExecutorStart/ExecutorFinish respectively.  If you really need to
suppress that and do it for yourself, pass EXEC_FLAG_SKIP_TRIGGERS to
ExecutorStart.

Also, refactor portal commit processing to allow for the possibility that
PortalDrop will invoke user-defined code.  I think this is not actually
necessary just yet, since the portal-execution-strategy logic forces any
non-pure-SELECT query to be run to completion before we will consider
committing.  But it seems like good future-proofing.
This commit is contained in:
Tom Lane
2011-02-27 13:43:29 -05:00
parent 67a5e727c8
commit a874fe7b4c
21 changed files with 350 additions and 222 deletions
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20
src/backend/tcop/pquery.c
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@ -181,11 +181,6 @@ ProcessQuery(PlannedStmt *plan,
GetActiveSnapshot(), InvalidSnapshot,
dest, params, 0);
/*
* Set up to collect AFTER triggers
*/
AfterTriggerBeginQuery();
/*
* Call ExecutorStart to prepare the plan for execution
*/
@ -231,17 +226,15 @@ ProcessQuery(PlannedStmt *plan,
}
}
/* Now take care of any queued AFTER triggers */
AfterTriggerEndQuery(queryDesc->estate);
PopActiveSnapshot();
/*
* Now, we close down all the scans and free allocated resources.
*/
ExecutorFinish(queryDesc);
ExecutorEnd(queryDesc);
FreeQueryDesc(queryDesc);
PopActiveSnapshot();
}
/*
@ -530,13 +523,6 @@ PortalStart(Portal portal, ParamListInfo params, Snapshot snapshot)
params,
0);
/*
* We do *not* call AfterTriggerBeginQuery() here. We assume
* that a SELECT cannot queue any triggers. It would be messy
* to support triggers since the execution of the portal may
* be interleaved with other queries.
*/
/*
* If it's a scrollable cursor, executor needs to support
* REWIND and backwards scan.