From 5a4904b1087795a6bb76ccb7d0ecf349dc10492f Mon Sep 17 00:00:00 2001 From: David Rowley Date: Fri, 1 Apr 2022 21:38:03 +1300 Subject: [PATCH 4/4] Use Generation memory contexts to store tuples in sorts The general usage pattern when we store tuples in tuplesort.c is that we store a series of tuples one by one then either perform a sort or spill them to disk. In the common case, there is no pfreeing of already stored tuples. For the common case since we do not individually pfree tuples, we have very little need for aset.c memory allocation behavior which maintains freelists and always rounds allocation sizes up to the next power of 2 size. Here we conditionally use generation.c contexts for storing tuples in tuplesort.c when the sort will never be bounded. Unfortunately, the memory context to store tuples is already created by the time any calls would be made to tuplesort_set_bound(), so here we add a new sort option that allows callers to specify if they're going to need a bounded sort or not. We'll use a standard aset.c allocator when this sort option is not set. Author: David Rowley Discussion: https://postgr.es/m/CAApHDvoH4ASzsAOyHcxkuY01Qf++8JJ0paw+03dk+W25tQEcNQ@mail.gmail.com --- src/backend/executor/nodeIncrementalSort.c | 6 ++++-- src/backend/executor/nodeSort.c | 2 ++ src/backend/utils/sort/tuplesort.c | 20 ++++++++++++++++---- src/include/utils/tuplesort.h | 3 +++ 4 files changed, 25 insertions(+), 6 deletions(-) diff --git a/src/backend/executor/nodeIncrementalSort.c b/src/backend/executor/nodeIncrementalSort.c index 4f50bc845da..3c5e8c9a969 100644 --- a/src/backend/executor/nodeIncrementalSort.c +++ b/src/backend/executor/nodeIncrementalSort.c @@ -315,7 +315,7 @@ switchToPresortedPrefixMode(PlanState *pstate) &(plannode->sort.nullsFirst[nPresortedCols]), work_mem, NULL, - TUPLESORT_NONE); + node->bounded ? TUPLESORT_ALLOWBOUNDED : TUPLESORT_NONE); node->prefixsort_state = prefixsort_state; } else @@ -616,7 +616,9 @@ ExecIncrementalSort(PlanState *pstate) plannode->sort.nullsFirst, work_mem, NULL, - TUPLESORT_NONE); + node->bounded ? + TUPLESORT_ALLOWBOUNDED : + TUPLESORT_NONE); node->fullsort_state = fullsort_state; } else diff --git a/src/backend/executor/nodeSort.c b/src/backend/executor/nodeSort.c index a113d737955..3c28d60c3ef 100644 --- a/src/backend/executor/nodeSort.c +++ b/src/backend/executor/nodeSort.c @@ -99,6 +99,8 @@ ExecSort(PlanState *pstate) if (node->randomAccess) tuplesortopts |= TUPLESORT_RANDOMACCESS; + if (node->bounded) + tuplesortopts |= TUPLESORT_ALLOWBOUNDED; if (node->datumSort) tuplesortstate = tuplesort_begin_datum(TupleDescAttr(tupDesc, 0)->atttypid, diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c index a0ab61e8f9a..613f55ca21b 100644 --- a/src/backend/utils/sort/tuplesort.c +++ b/src/backend/utils/sort/tuplesort.c @@ -842,11 +842,21 @@ tuplesort_begin_batch(Tuplesortstate *state) * eases memory management. Resetting at key points reduces * fragmentation. Note that the memtuples array of SortTuples is allocated * in the parent context, not this context, because there is no need to - * free memtuples early. + * free memtuples early. For bounded sorts, tuples may be pfreed in any + * order, so we use a regular aset.c context so that it can make use of + * free'd memory. When the sort is not bounded, we make use of a + * generation.c context as this keeps allocations more compact with less + * wastage. Allocations are also slightly more CPU efficient. */ - state->tuplecontext = AllocSetContextCreate(state->sortcontext, - "Caller tuples", - ALLOCSET_DEFAULT_SIZES); + if (state->sortopt & TUPLESORT_ALLOWBOUNDED) + state->tuplecontext = AllocSetContextCreate(state->sortcontext, + "Caller tuples", + ALLOCSET_DEFAULT_SIZES); + else + state->tuplecontext = GenerationContextCreate(state->sortcontext, + "Caller tuples", + ALLOCSET_DEFAULT_SIZES); + state->status = TSS_INITIAL; state->bounded = false; @@ -1337,6 +1347,8 @@ tuplesort_set_bound(Tuplesortstate *state, int64 bound) { /* Assert we're called before loading any tuples */ Assert(state->status == TSS_INITIAL && state->memtupcount == 0); + /* Assert we allow bounded sorts */ + Assert(state->sortopt & TUPLESORT_ALLOWBOUNDED); /* Can't set the bound twice, either */ Assert(!state->bounded); /* Also, this shouldn't be called in a parallel worker */ diff --git a/src/include/utils/tuplesort.h b/src/include/utils/tuplesort.h index 345f4ce8024..364cf132fcb 100644 --- a/src/include/utils/tuplesort.h +++ b/src/include/utils/tuplesort.h @@ -92,6 +92,9 @@ typedef enum /* specifies whether non-sequential access to the sort result is required */ #define TUPLESORT_RANDOMACCESS (1 << 0) +/* specifies if the tuplesort is able to support bounded sorts */ +#define TUPLESORT_ALLOWBOUNDED (1 << 1) + typedef struct TuplesortInstrumentation { TuplesortMethod sortMethod; /* sort algorithm used */ -- 2.17.1