Attached is a patch that replaces a bunch of places where StringInfos

are unnecessarily allocated on the heap rather than the stack. If the
StringInfo doesn't outlive the stack frame in which it is created,
there is no need to allocate it on the heap via makeStringInfo() --
stack allocation is faster.  While it's not a big deal unless the
code is in a critical path, I don't see a reason not to save a few
cycles -- using stack allocation is not less readable.

I also cleaned up a bit of code along the way: moved variable
declarations into a more tightly-enclosing scope where possible,
fixed some pointless copying of strings in dblink, etc.

1 files changed, 11 insertions, 13 deletions

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 755a64a9446..767d4c9f806 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.144 2006/02/28 04:10:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.145 2006/03/01 06:51:01 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -232,7 +232,7 @@ ExplainOnePlan(QueryDesc *queryDesc, ExplainStmt *stmt,
 	instr_time	starttime;
 	double		totaltime = 0;
 	ExplainState *es;
-	StringInfo	str;
+	StringInfoData buf;
 	int			eflags;
 
 	INSTR_TIME_SET_CURRENT(starttime);
@@ -285,9 +285,8 @@ ExplainOnePlan(QueryDesc *queryDesc, ExplainStmt *stmt,
 		}
 	}
 
-	str = makeStringInfo();
-
-	explain_outNode(str, queryDesc->plantree, queryDesc->planstate,
+	initStringInfo(&buf);
+	explain_outNode(&buf, queryDesc->plantree, queryDesc->planstate,
 					NULL, 0, es);
 
 	/*
@@ -335,18 +334,18 @@ ExplainOnePlan(QueryDesc *queryDesc, ExplainStmt *stmt,
 				if (trig->tgisconstraint &&
 				(conname = GetConstraintNameForTrigger(trig->tgoid)) != NULL)
 				{
-					appendStringInfo(str, "Trigger for constraint %s",
+					appendStringInfo(&buf, "Trigger for constraint %s",
 									 conname);
 					pfree(conname);
 				}
 				else
-					appendStringInfo(str, "Trigger %s", trig->tgname);
+					appendStringInfo(&buf, "Trigger %s", trig->tgname);
 
 				if (numrels > 1)
-					appendStringInfo(str, " on %s",
+					appendStringInfo(&buf, " on %s",
 							RelationGetRelationName(rInfo->ri_RelationDesc));
 
-				appendStringInfo(str, ": time=%.3f calls=%.0f\n",
+				appendStringInfo(&buf, ": time=%.3f calls=%.0f\n",
 								 1000.0 * instr->total,
 								 instr->ntuples);
 			}
@@ -370,12 +369,11 @@ ExplainOnePlan(QueryDesc *queryDesc, ExplainStmt *stmt,
 	totaltime += elapsed_time(&starttime);
 
 	if (stmt->analyze)
-		appendStringInfo(str, "Total runtime: %.3f ms\n",
+		appendStringInfo(&buf, "Total runtime: %.3f ms\n",
 						 1000.0 * totaltime);
-	do_text_output_multiline(tstate, str->data);
+	do_text_output_multiline(tstate, buf.data);
 
-	pfree(str->data);
-	pfree(str);
+	pfree(buf.data);
 	pfree(es);
 }