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In the executor, use an array of pointers to access the rangetable.

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Instead of doing a lot of list_nth() accesses to es_range_table,
create a flattened pointer array during executor startup and index
into that to get at individual RangeTblEntrys.

This eliminates one source of O(N^2) behavior with lots of partitions.
(I'm not exactly convinced that it's the most important source, but
it's an easy one to fix.)

Amit Langote and David Rowley

Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp
This commit is contained in:
Tom Lane
2018-10-04 15:48:17 -04:00
parent 9ddef36278
commit d73f4c74dd
11 changed files with 87 additions and 52 deletions
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6
src/backend/executor/execExprInterp.c
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@ -3934,10 +3934,10 @@ ExecEvalWholeRowVar(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
* perhaps other places.)
*/
if (econtext->ecxt_estate &&
variable->varno <= list_length(econtext->ecxt_estate->es_range_table))
variable->varno <= econtext->ecxt_estate->es_range_table_size)
{
RangeTblEntry *rte = rt_fetch(variable->varno,
econtext->ecxt_estate->es_range_table);
RangeTblEntry *rte = exec_rt_fetch(variable->varno,
econtext->ecxt_estate);
if (rte->eref)
ExecTypeSetColNames(output_tupdesc, rte->eref->colnames);