Re: Duplicated assignment of slot_name in walsender.c - Mailing list pgsql-hackers

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 reqstatic
voidCreateReplicationSlot(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/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services