Re: Duplicated assignment of slot_name in walsender.c

Andres Freund wrote:

> That seems fairly insignificant. For one this is a rather infrequent and
> expensive operation, for another every decent compiler can optimize
> those away. Note that those duplicate strlen() calls are there in a lot
> of places in walsender.c

diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index c6043cd..5487cc0 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -762,10 +762,10 @@ logical_read_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr, int req
 static void
 CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 {
-	const char *slot_name;
 	const char *snapshot_name = NULL;
 	char		xpos[MAXFNAMELEN];
 	StringInfoData buf;
+	int			len;
 
 	Assert(!MyReplicationSlot);
 
@@ -791,14 +791,11 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 
 	initStringInfo(&output_message);
 
-	slot_name = NameStr(MyReplicationSlot->data.name);
-
 	if (cmd->kind == REPLICATION_KIND_LOGICAL)
 	{
 		LogicalDecodingContext *ctx;
 
-		ctx = CreateInitDecodingContext(
-										cmd->plugin, NIL,
+		ctx = CreateInitDecodingContext(cmd->plugin, NIL,
 										logical_read_xlog_page,
 										WalSndPrepareWrite, WalSndWriteData);
 
@@ -834,7 +831,6 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 		ReplicationSlotSave();
 	}
 
-	slot_name = NameStr(MyReplicationSlot->data.name);
 	snprintf(xpos, sizeof(xpos), "%X/%X",
 			 (uint32) (MyReplicationSlot->data.confirmed_flush >> 32),
 			 (uint32) MyReplicationSlot->data.confirmed_flush);
@@ -885,18 +881,21 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	pq_sendint(&buf, 4, 2);		/* # of columns */
 
 	/* slot_name */
-	pq_sendint(&buf, strlen(slot_name), 4);		/* col1 len */
-	pq_sendbytes(&buf, slot_name, strlen(slot_name));
+	len = strlen(NameStr(MyReplicationSlot->data.name));
+	pq_sendint(&buf, len, 4);		/* col1 len */
+	pq_sendbytes(&buf, NameStr(MyReplicationSlot->data.name), len);
 
 	/* consistent wal location */
-	pq_sendint(&buf, strlen(xpos), 4);	/* col2 len */
-	pq_sendbytes(&buf, xpos, strlen(xpos));
+	len = strlen(xpos);
+	pq_sendint(&buf, len, 4);	/* col2 len */
+	pq_sendbytes(&buf, xpos, len);
 
 	/* snapshot name */
 	if (snapshot_name != NULL)
 	{
-		pq_sendint(&buf, strlen(snapshot_name), 4);		/* col3 len */
-		pq_sendbytes(&buf, snapshot_name, strlen(snapshot_name));
+		len = strlen(snapshot_name);
+		pq_sendint(&buf, len, 4);		/* col3 len */
+		pq_sendbytes(&buf, snapshot_name, len);
 	}
 	else
 		pq_sendint(&buf, -1, 4);	/* col3 len, NULL */
@@ -904,8 +903,9 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 	/* plugin */
 	if (cmd->plugin != NULL)
 	{
-		pq_sendint(&buf, strlen(cmd->plugin), 4);		/* col4 len */
-		pq_sendbytes(&buf, cmd->plugin, strlen(cmd->plugin));
+		len = strlen(cmd->plugin);
+		pq_sendint(&buf, len, 4);		/* col4 len */
+		pq_sendbytes(&buf, cmd->plugin, len);
 	}
 	else
 		pq_sendint(&buf, -1, 4);	/* col4 len, NULL */

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
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