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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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4
src/include/optimizer/cost.h
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@@ -86,6 +86,10 @@ extern void cost_sort(Path *path, PlannerInfo *root,
List *pathkeys, Cost input_cost, double tuples, int width,
Cost comparison_cost, int sort_mem,
double limit_tuples);
extern void cost_merge_append(Path *path, PlannerInfo *root,
List *pathkeys, int n_streams,
Cost input_startup_cost, Cost input_total_cost,
double tuples);
extern void cost_material(Path *path,
Cost input_startup_cost, Cost input_total_cost,
double tuples, int width);