Hi,
Today, I discovered that when building a btree index, the btree code
uses index_form_tuple() to create an index tuple from the heap tuple,
calls tuplesort_putindextuple() to copy that tuple into the sort's
memory context, and then frees the original one it built. This seemed
inefficient, so I wrote a patch to eliminate the tuple copying. It
works by adding a function tuplesort_putindextuplevalues(), which
builds the tuple in the sort's memory context and thus avoids the need
for a separate copy. I'm not sure if that's the best approach, but
the optimization seems wortwhile.
I tested it by repeatedly executing "REINDEX INDEX
pgbench_accounts_pkey" on a PPC64 machine. pgbench_accounts contains
10 million records. With unpatched master as of
b2f7bd72c4d3e80065725c72e85778d5f4bdfd4a, I got times of 6.159s,
6.177s, and 6.201s. With the attached patch, I got times of 5.787s,
5.972s, and 5.913s, a savings of almost 5%. Not bad considering the
amount of work involved.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index 542ed43..0743474 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -171,28 +171,21 @@ btbuildCallback(Relation index,
void *state)
{
BTBuildState *buildstate = (BTBuildState *) state;
- IndexTuple itup;
-
- /* form an index tuple and point it at the heap tuple */
- itup = index_form_tuple(RelationGetDescr(index), values, isnull);
- itup->t_tid = htup->t_self;
/*
* insert the index tuple into the appropriate spool file for subsequent
* processing
*/
if (tupleIsAlive || buildstate->spool2 == NULL)
- _bt_spool(itup, buildstate->spool);
+ _bt_spool(buildstate->spool, htup->t_self, values, isnull);
else
{
/* dead tuples are put into spool2 */
buildstate->haveDead = true;
- _bt_spool(itup, buildstate->spool2);
+ _bt_spool(buildstate->spool2, htup->t_self, values, isnull);
}
buildstate->indtuples += 1;
-
- pfree(itup);
}
/*
diff --git a/src/backend/access/nbtree/nbtsort.c b/src/backend/access/nbtree/nbtsort.c
index 9ddc275..8cd3a91 100644
--- a/src/backend/access/nbtree/nbtsort.c
+++ b/src/backend/access/nbtree/nbtsort.c
@@ -185,9 +185,10 @@ _bt_spooldestroy(BTSpool *btspool)
* spool an index entry into the sort file.
*/
void
-_bt_spool(IndexTuple itup, BTSpool *btspool)
+_bt_spool(BTSpool *btspool, ItemPointerData self, Datum *values, bool *isnull)
{
- tuplesort_putindextuple(btspool->sortstate, itup);
+ tuplesort_putindextuplevalues(btspool->sortstate, btspool->index,
+ self, values, isnull);
}
/*
diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 8b520c1..3b0a06c 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -1150,6 +1150,29 @@ tuplesort_putindextuple(Tuplesortstate *state, IndexTuple tuple)
*/
COPYTUP(state, &stup, (void *) tuple);
+ MemoryContextSwitchTo(oldcontext);
+}
+
+/*
+ * Collect one index tuple while collecting input data for sort, building
+ * it from caller-supplied values.
+ */
+void
+tuplesort_putindextuplevalues(Tuplesortstate *state, Relation rel,
+ ItemPointerData self, Datum *values,
+ bool *isnull)
+{
+ MemoryContext oldcontext = MemoryContextSwitchTo(state->sortcontext);
+ SortTuple stup;
+
+ stup.tuple = index_form_tuple(RelationGetDescr(rel), values, isnull);
+ ((IndexTuple) stup.tuple)->t_tid = self;
+ USEMEM(state, GetMemoryChunkSpace(stup.tuple));
+ /* set up first-column key value */
+ stup.datum1 = index_getattr((IndexTuple) stup.tuple,
+ 1,
+ RelationGetDescr(state->indexRel),
+ &stup.isnull1);
puttuple_common(state, &stup);
MemoryContextSwitchTo(oldcontext);
diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index 1a8b16d..5ef1f9b 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -717,7 +717,8 @@ typedef struct BTSpool BTSpool; /* opaque type known only within nbtsort.c */
extern BTSpool *_bt_spoolinit(Relation heap, Relation index,
bool isunique, bool isdead);
extern void _bt_spooldestroy(BTSpool *btspool);
-extern void _bt_spool(IndexTuple itup, BTSpool *btspool);
+extern void _bt_spool(BTSpool *btspool, ItemPointerData self,
+ Datum *values, bool *isnull);
extern void _bt_leafbuild(BTSpool *btspool, BTSpool *spool2);
/*
diff --git a/src/include/utils/tuplesort.h b/src/include/utils/tuplesort.h
index 05445f0..2b62a98 100644
--- a/src/include/utils/tuplesort.h
+++ b/src/include/utils/tuplesort.h
@@ -85,6 +85,9 @@ extern void tuplesort_puttupleslot(Tuplesortstate *state,
TupleTableSlot *slot);
extern void tuplesort_putheaptuple(Tuplesortstate *state, HeapTuple tup);
extern void tuplesort_putindextuple(Tuplesortstate *state, IndexTuple tuple);
+extern void tuplesort_putindextuplevalues(Tuplesortstate *state,
+ Relation rel, ItemPointerData self,
+ Datum *values, bool *isnull);
extern void tuplesort_putdatum(Tuplesortstate *state, Datum val,
bool isNull);
--
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