From 7470eb62b45dd5ee5280d8f834a910a64c8bcc85 Mon Sep 17 00:00:00 2001 From: Jeff Davis Date: Tue, 4 Mar 2025 15:13:22 -0800 Subject: [PATCH v8 4/7] Remove 'additional' pointer from TupleHashEntryData. Reduces memory required for hash aggregation by avoiding an allocation and a pointer in the TupleHashEntryData structure. That structure is used for all buckets, whether occupied or not, so the savings is substantial. Discussion: https://postgr.es/m/AApHDvpN4v3t_sdz4dvrv1Fx_ZPw=twSnxuTEytRYP7LFz5K9A@mail.gmail.com Reviewed-by: David Rowley --- src/backend/executor/execGrouping.c | 32 ++++++++++++++++++++++------- src/include/executor/executor.h | 5 ++++- src/include/nodes/execnodes.h | 1 - 3 files changed, 29 insertions(+), 9 deletions(-) diff --git a/src/backend/executor/execGrouping.c b/src/backend/executor/execGrouping.c index a9d212aaec6..5c06cc6da40 100644 --- a/src/backend/executor/execGrouping.c +++ b/src/backend/executor/execGrouping.c @@ -481,15 +481,33 @@ LookupTupleHashEntry_internal(TupleHashTable hashtable, TupleTableSlot *slot, else { /* created new entry */ - *isnew = true; + bool shouldFree; + char *mem; + MinimalTuple mtup; - MemoryContextSwitchTo(hashtable->tablecxt); + *isnew = true; - entry->firstTuple = ExecCopySlotMinimalTuple(slot); - if (hashtable->additionalsize > 0) - entry->additional = palloc0(hashtable->additionalsize); - else - entry->additional = NULL; + MemoryContextSwitchTo(hashtable->tempcxt); + + /* ignore shouldFree, because we're in the temp context anyway */ + mtup = ExecFetchSlotMinimalTuple(slot, &shouldFree); + + /* + * Allocate enough memory in the tablecxt for the additionalsize + * followed by the tuple. Clear the additional data, and copy the + * tuple. + * + * The caller can get a pointer to the additional data with + * TupleHashEntryGetAdditional(), and store arbitrary data there. + * Placing both the tuple and additional data in the same + * allocation avoids the need to store an extra pointer in + * TupleHashEntryData or allocate an additional chunk. + */ + mem = MemoryContextAlloc(hashtable->tablecxt, + mtup->t_len + hashtable->additionalsize); + memset(mem, 0, hashtable->additionalsize); + entry->firstTuple = (MinimalTuple) (mem + hashtable->additionalsize); + memcpy(entry->firstTuple, mtup, mtup->t_len); } } else diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h index d0aa0e94241..90fa466dea4 100644 --- a/src/include/executor/executor.h +++ b/src/include/executor/executor.h @@ -188,7 +188,10 @@ TupleHashEntryGetTuple(TupleHashEntry entry) static inline void * TupleHashEntryGetAdditional(TupleHashTable hashtable, TupleHashEntry entry) { - return entry->additional; + if (hashtable->additionalsize > 0) + return (char *) entry->firstTuple - hashtable->additionalsize; + else + return NULL; } #endif diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h index b9ca5f7f5fa..e93533dbbc5 100644 --- a/src/include/nodes/execnodes.h +++ b/src/include/nodes/execnodes.h @@ -840,7 +840,6 @@ typedef struct TupleHashTableData *TupleHashTable; typedef struct TupleHashEntryData { MinimalTuple firstTuple; /* copy of first tuple in this group */ - void *additional; /* user data */ uint32 status; /* hash status */ uint32 hash; /* hash value (cached) */ } TupleHashEntryData; -- 2.34.1