From c38b75947e015afdd2a18d099f52d29748734e32 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 23 Aug 2009 18:26:08 +0000
Subject: [PATCH] Tweak ExecIndexEvalRuntimeKeys to forcibly detoast any
toasted comparison values before they get passed to the index access method.
This avoids repeated detoastings that will otherwise ensue as the comparison
value is examined by various index support functions. We have seen a couple
of reports of cases where repeated detoastings result in an
order-of-magnitude slowdown, so it seems worth adding a bit of extra logic to
prevent this.
I had previously proposed trying to avoid duplicate detoastings in general,
but this fix takes care of what seems the most important case in practice
with very little effort or risk.
Back-patch to 8.4 so that the PostGIS folk won't have to wait a year to
have this fix in a production release. (The issue exists further back,
of course, but the code's diverged enough to make backpatching further a
higher-risk action. Also it appears that the possible gains may be limited
in prior releases because of different handling of lossy operators.)
---
src/backend/executor/nodeIndexscan.c | 86 +++++++++++++++++-----------
src/include/nodes/execnodes.h | 3 +-
2 files changed, 56 insertions(+), 33 deletions(-)
diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index 48290d14cb5..2a9ccf82320 100644
--- a/src/backend/executor/nodeIndexscan.c
+++ b/src/backend/executor/nodeIndexscan.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.133 2009/07/18 19:15:41 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.134 2009/08/23 18:26:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -238,6 +238,10 @@ ExecIndexEvalRuntimeKeys(ExprContext *econtext,
IndexRuntimeKeyInfo *runtimeKeys, int numRuntimeKeys)
{
int j;
+ MemoryContext oldContext;
+
+ /* We want to keep the key values in per-tuple memory */
+ oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
for (j = 0; j < numRuntimeKeys; j++)
{
@@ -256,18 +260,32 @@ ExecIndexEvalRuntimeKeys(ExprContext *econtext,
* econtext->ecxt_per_tuple_memory. We assume that the outer tuple
* will stay put throughout our scan. If this is wrong, we could copy
* the result into our context explicitly, but I think that's not
- * necessary...
+ * necessary.
+ *
+ * It's also entirely possible that the result of the eval is a
+ * toasted value. In this case we should forcibly detoast it,
+ * to avoid repeat detoastings each time the value is examined
+ * by an index support function.
*/
- scanvalue = ExecEvalExprSwitchContext(key_expr,
- econtext,
- &isNull,
- NULL);
- scan_key->sk_argument = scanvalue;
+ scanvalue = ExecEvalExpr(key_expr,
+ econtext,
+ &isNull,
+ NULL);
if (isNull)
+ {
+ scan_key->sk_argument = scanvalue;
scan_key->sk_flags |= SK_ISNULL;
+ }
else
+ {
+ if (runtimeKeys[j].key_toastable)
+ scanvalue = PointerGetDatum(PG_DETOAST_DATUM(scanvalue));
+ scan_key->sk_argument = scanvalue;
scan_key->sk_flags &= ~SK_ISNULL;
+ }
}
+
+ MemoryContextSwitchTo(oldContext);
}
/*
@@ -795,6 +813,8 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
runtime_keys[n_runtime_keys].scan_key = this_scan_key;
runtime_keys[n_runtime_keys].key_expr =
ExecInitExpr(rightop, planstate);
+ runtime_keys[n_runtime_keys].key_toastable =
+ TypeIsToastable(op_righttype);
n_runtime_keys++;
scanvalue = (Datum) 0;
}
@@ -843,6 +863,31 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
varattno = ((Var *) leftop)->varattno;
+ /*
+ * We have to look up the operator's associated btree support
+ * function
+ */
+ opno = lfirst_oid(opnos_cell);
+ opnos_cell = lnext(opnos_cell);
+
+ if (index->rd_rel->relam != BTREE_AM_OID ||
+ varattno < 1 || varattno > index->rd_index->indnatts)
+ elog(ERROR, "bogus RowCompare index qualification");
+ opfamily = index->rd_opfamily[varattno - 1];
+
+ get_op_opfamily_properties(opno, opfamily,
+ &op_strategy,
+ &op_lefttype,
+ &op_righttype);
+
+ if (op_strategy != rc->rctype)
+ elog(ERROR, "RowCompare index qualification contains wrong operator");
+
+ opfuncid = get_opfamily_proc(opfamily,
+ op_lefttype,
+ op_righttype,
+ BTORDER_PROC);
+
/*
* rightop is the constant or variable comparison value
*/
@@ -867,35 +912,12 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
runtime_keys[n_runtime_keys].scan_key = this_sub_key;
runtime_keys[n_runtime_keys].key_expr =
ExecInitExpr(rightop, planstate);
+ runtime_keys[n_runtime_keys].key_toastable =
+ TypeIsToastable(op_righttype);
n_runtime_keys++;
scanvalue = (Datum) 0;
}
- /*
- * We have to look up the operator's associated btree support
- * function
- */
- opno = lfirst_oid(opnos_cell);
- opnos_cell = lnext(opnos_cell);
-
- if (index->rd_rel->relam != BTREE_AM_OID ||
- varattno < 1 || varattno > index->rd_index->indnatts)
- elog(ERROR, "bogus RowCompare index qualification");
- opfamily = index->rd_opfamily[varattno - 1];
-
- get_op_opfamily_properties(opno, opfamily,
- &op_strategy,
- &op_lefttype,
- &op_righttype);
-
- if (op_strategy != rc->rctype)
- elog(ERROR, "RowCompare index qualification contains wrong operator");
-
- opfuncid = get_opfamily_proc(opfamily,
- op_lefttype,
- op_righttype,
- BTORDER_PROC);
-
/*
* initialize the subsidiary scan key's fields appropriately
*/
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 1b60bda4691..742ff325752 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.206 2009/08/06 20:44:31 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.207 2009/08/23 18:26:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1084,6 +1084,7 @@ typedef struct
{
ScanKey scan_key; /* scankey to put value into */
ExprState *key_expr; /* expr to evaluate to get value */
+ bool key_toastable; /* is expr's result a toastable datatype? */
} IndexRuntimeKeyInfo;
typedef struct
--
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