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, 24 insertions, 27 deletions

diff --git a/contrib/tablefunc/tablefunc.c b/contrib/tablefunc/tablefunc.c
index 0beb44f5845..aacc949ff28 100644
--- a/contrib/tablefunc/tablefunc.c
+++ b/contrib/tablefunc/tablefunc.c
@@ -1260,13 +1260,10 @@ build_tuplestore_recursively(char *key_fld,
 {
 	TupleDesc	tupdesc = attinmeta->tupdesc;
 	MemoryContext oldcontext;
-	StringInfo	sql = makeStringInfo();
 	int			ret;
 	int			proc;
 	int			serial_column;
-	StringInfo	branchstr = NULL;
-	StringInfo	chk_branchstr = NULL;
-	StringInfo	chk_current_key = NULL;
+	StringInfoData	sql;
 	char	  **values;
 	char	   *current_key;
 	char	   *current_key_parent;
@@ -1278,17 +1275,12 @@ build_tuplestore_recursively(char *key_fld,
 	if (max_depth > 0 && level > max_depth)
 		return tupstore;
 
-	/* start a new branch */
-	branchstr = makeStringInfo();
-
-	/* need these to check for recursion */
-	chk_branchstr = makeStringInfo();
-	chk_current_key = makeStringInfo();
+	initStringInfo(&sql);
 
 	/* Build initial sql statement */
 	if (!show_serial)
 	{
-		appendStringInfo(sql, "SELECT %s, %s FROM %s WHERE %s = %s AND %s IS NOT NULL AND %s <> %s",
+		appendStringInfo(&sql, "SELECT %s, %s FROM %s WHERE %s = %s AND %s IS NOT NULL AND %s <> %s",
 						 key_fld,
 						 parent_key_fld,
 						 relname,
@@ -1299,7 +1291,7 @@ build_tuplestore_recursively(char *key_fld,
 	}
 	else
 	{
-		appendStringInfo(sql, "SELECT %s, %s FROM %s WHERE %s = %s AND %s IS NOT NULL AND %s <> %s ORDER BY %s",
+		appendStringInfo(&sql, "SELECT %s, %s FROM %s WHERE %s = %s AND %s IS NOT NULL AND %s <> %s ORDER BY %s",
 						 key_fld,
 						 parent_key_fld,
 						 relname,
@@ -1359,7 +1351,7 @@ build_tuplestore_recursively(char *key_fld,
 	}
 
 	/* Retrieve the desired rows */
-	ret = SPI_execute(sql->data, true, 0);
+	ret = SPI_execute(sql.data, true, 0);
 	proc = SPI_processed;
 
 	/* Check for qualifying tuples */
@@ -1369,6 +1361,9 @@ build_tuplestore_recursively(char *key_fld,
 		SPITupleTable *tuptable = SPI_tuptable;
 		TupleDesc	spi_tupdesc = tuptable->tupdesc;
 		int			i;
+		StringInfoData	branchstr;
+		StringInfoData	chk_branchstr;
+		StringInfoData	chk_current_key;
 
 		/* First time through, do a little more setup */
 		if (level == 0)
@@ -1389,28 +1384,35 @@ build_tuplestore_recursively(char *key_fld,
 
 		for (i = 0; i < proc; i++)
 		{
+			/* start a new branch */
+			initStringInfo(&branchstr);
+
+			/* need these to check for recursion */
+			initStringInfo(&chk_branchstr);
+			initStringInfo(&chk_current_key);
+
 			/* initialize branch for this pass */
-			appendStringInfo(branchstr, "%s", branch);
-			appendStringInfo(chk_branchstr, "%s%s%s", branch_delim, branch, branch_delim);
+			appendStringInfo(&branchstr, "%s", branch);
+			appendStringInfo(&chk_branchstr, "%s%s%s", branch_delim, branch, branch_delim);
 
 			/* get the next sql result tuple */
 			spi_tuple = tuptable->vals[i];
 
 			/* get the current key and parent */
 			current_key = SPI_getvalue(spi_tuple, spi_tupdesc, 1);
-			appendStringInfo(chk_current_key, "%s%s%s", branch_delim, current_key, branch_delim);
+			appendStringInfo(&chk_current_key, "%s%s%s", branch_delim, current_key, branch_delim);
 			current_key_parent = pstrdup(SPI_getvalue(spi_tuple, spi_tupdesc, 2));
 
 			/* get the current level */
 			sprintf(current_level, "%d", level);
 
 			/* check to see if this key is also an ancestor */
-			if (strstr(chk_branchstr->data, chk_current_key->data))
+			if (strstr(chk_branchstr.data, chk_current_key.data))
 				elog(ERROR, "infinite recursion detected");
 
 			/* OK, extend the branch */
-			appendStringInfo(branchstr, "%s%s", branch_delim, current_key);
-			current_branch = branchstr->data;
+			appendStringInfo(&branchstr, "%s%s", branch_delim, current_key);
+			current_branch = branchstr.data;
 
 			/* build a tuple */
 			values[0] = pstrdup(current_key);
@@ -1461,14 +1463,9 @@ build_tuplestore_recursively(char *key_fld,
 													tupstore);
 
 			/* reset branch for next pass */
-			xpfree(branchstr->data);
-			initStringInfo(branchstr);
-
-			xpfree(chk_branchstr->data);
-			initStringInfo(chk_branchstr);
-
-			xpfree(chk_current_key->data);
-			initStringInfo(chk_current_key);
+			xpfree(branchstr.data);
+			xpfree(chk_branchstr.data);
+			xpfree(chk_current_key.data);
 		}
 	}