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Support MergeAppend plans, to allow sorted output from append relations.

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This patch eliminates the former need to sort the output of an Append scan
when an ordered scan of an inheritance tree is wanted.  This should be
particularly useful for fast-start cases such as queries with LIMIT.

Original patch by Greg Stark, with further hacking by Hans-Jurgen Schonig,
Robert Haas, and Tom Lane.
This commit is contained in:
Tom Lane
2010-10-14 16:56:39 -04:00
parent 30e749dece
commit 11cad29c91
26 changed files with 1316 additions and 68 deletions
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14
src/backend/utils/adt/ruleutils.c
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@ -2174,15 +2174,17 @@ set_deparse_planstate(deparse_namespace *dpns, PlanState *ps)
dpns->planstate = ps;
/*
* We special-case Append to pretend that the first child plan is the
* OUTER referent; we have to interpret OUTER Vars in the Append's tlist
* according to one of the children, and the first one is the most natural
* choice. Likewise special-case ModifyTable to pretend that the first
* child plan is the OUTER referent; this is to support RETURNING lists
* containing references to non-target relations.
* We special-case Append and MergeAppend to pretend that the first child
* plan is the OUTER referent; we have to interpret OUTER Vars in their
* tlists according to one of the children, and the first one is the most
* natural choice. Likewise special-case ModifyTable to pretend that the
* first child plan is the OUTER referent; this is to support RETURNING
* lists containing references to non-target relations.
*/
if (IsA(ps, AppendState))
dpns->outer_planstate = ((AppendState *) ps)->appendplans[0];
else if (IsA(ps, MergeAppendState))
dpns->outer_planstate = ((MergeAppendState *) ps)->mergeplans[0];
else if (IsA(ps, ModifyTableState))
dpns->outer_planstate = ((ModifyTableState *) ps)->mt_plans[0];
else