From: Robert Haas <rhaas@postgresql.org>
Date: Thu, 11 Apr 2013 19:20:24 +0000 (+0000)
Subject: Avoid PG_TRY/PG_CATCH overhead if stringinfo is already large enough.
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=refs%2Fheads%2Fcopy_hack;p=users%2Frhaas%2Fpostgres.git

Avoid PG_TRY/PG_CATCH overhead if stringinfo is already large enough.
---

diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index d9dda21d93..b0406bba46 100644
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -1131,19 +1131,22 @@ pq_getmessage(StringInfo s, int maxlen)
 		 * large message), we will elog(ERROR), but we want to discard the
 		 * message body so as not to lose communication sync.
 		 */
-		PG_TRY();
+		if (!isStringInfoLargeEnough(s, len))
 		{
-			enlargeStringInfo(s, len);
-		}
-		PG_CATCH();
-		{
-			if (pq_discardbytes(len) == EOF)
-				ereport(COMMERROR,
-						(errcode(ERRCODE_PROTOCOL_VIOLATION),
-						 errmsg("incomplete message from client")));
-			PG_RE_THROW();
+			PG_TRY();
+			{
+				enlargeStringInfo(s, len);
+			}
+			PG_CATCH();
+			{
+				if (pq_discardbytes(len) == EOF)
+					ereport(COMMERROR,
+							(errcode(ERRCODE_PROTOCOL_VIOLATION),
+							 errmsg("incomplete message from client")));
+				PG_RE_THROW();
+			}
+			PG_END_TRY();
 		}
-		PG_END_TRY();
 
 		/* And grab the message */
 		if (pq_getbytes(s->data, len) == EOF)
diff --git a/src/include/lib/stringinfo.h b/src/include/lib/stringinfo.h
index ecb693fcc2..f795680777 100644
--- a/src/include/lib/stringinfo.h
+++ b/src/include/lib/stringinfo.h
@@ -153,4 +153,11 @@ extern void appendBinaryStringInfo(StringInfo str,
  */
 extern void enlargeStringInfo(StringInfo str, int needed);
 
+/*------------------------
+ * isStringInfoLargeEnough 
+ * Test whether a StringInfo's buffer can hold at least 'needed' more bytes.
+ */
+#define isStringInfoLargeEnough(str,needed) \
+	((needed) < (str)->maxlen - ((str)->len + 1))
+
 #endif   /* STRINGINFO_H */