summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorTom Lane2009-08-23 18:26:08 +0000
committerTom Lane2009-08-23 18:26:08 +0000
commitd44de130b908e0568213fcfb9ccd8cdd35d82e48 (patch)
treee220e63332bd12f91396f6a05669aaf8092b840b
parent58729462931e6e8ffb2c982c1797d7d423f377af (diff)
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.)
-rw-r--r--src/backend/executor/nodeIndexscan.c84
-rw-r--r--src/include/nodes/execnodes.h1
2 files changed, 54 insertions, 31 deletions
diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index e2ad067049..d8ec8b34f5 100644
--- a/src/backend/executor/nodeIndexscan.c
+++ b/src/backend/executor/nodeIndexscan.c
@@ -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;
}
@@ -844,6 +864,31 @@ 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
*/
rightop = (Expr *) lfirst(rargs_cell);
@@ -867,36 +912,13 @@ 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
*/
ScanKeyEntryInitialize(this_sub_key,
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 48beaa4709..34fcf6899a 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -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