Represent command completion tags as structs

The backend was using strings to represent command tags and doing string
comparisons in multiple places, but that's slow and unhelpful.  Create a
new command list with a supporting structure to use instead; this is
stored in a tag-list-file that can be tailored to specific purposes with
a caller-definable C macro, similar to what we do for WAL resource
managers.  The first first such uses are a new CommandTag enum and a
CommandTagBehavior struct.

Replace numerous occurrences of char *completionTag with a
QueryCompletion struct so that the code no longer stores information
about completed queries in a cstring.  Only at the last moment, in
EndCommand(), does this get converted to a string.

EventTriggerCacheItem no longer holds an array of palloc’d tag strings
in sorted order, but rather just a Bitmapset over the CommandTags.

Author: Mark Dilger, with unsolicited help from Álvaro Herrera
Reviewed-by: John Naylor, Tom Lane
Discussion: https://postgr.es/m/981A9DB4-3F0C-4DA5-88AD-CB9CFF4D6CAD@enterprisedb.com

2 files changed, 15 insertions, 5 deletions

diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index 0ddc707def..c2e5e3abf8 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -100,7 +100,7 @@ LogicalDecodingProcessRecord(LogicalDecodingContext *ctx, XLogReaderState *recor
 	buf.record = record;
 
 	/* cast so we get a warning when new rmgrs are added */
-	switch ((RmgrIds) XLogRecGetRmid(record))
+	switch ((RmgrId) XLogRecGetRmid(record))
 	{
 			/*
 			 * Rmgrs we care about for logical decoding. Add new rmgrs in
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index abb533b9d0..ae4a9cbe11 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -1074,8 +1074,11 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 static void
 DropReplicationSlot(DropReplicationSlotCmd *cmd)
 {
+	QueryCompletion qc;
+
 	ReplicationSlotDrop(cmd->slotname, !cmd->wait);
-	EndCommand("DROP_REPLICATION_SLOT", DestRemote);
+	SetQueryCompletion(&qc, CMDTAG_DROP_REPLICATION_SLOT, 0);
+	EndCommand(&qc, DestRemote, false);
 }
 
 /*
@@ -1086,6 +1089,7 @@ static void
 StartLogicalReplication(StartReplicationCmd *cmd)
 {
 	StringInfoData buf;
+	QueryCompletion qc;
 
 	/* make sure that our requirements are still fulfilled */
 	CheckLogicalDecodingRequirements();
@@ -1160,7 +1164,8 @@ StartLogicalReplication(StartReplicationCmd *cmd)
 	WalSndSetState(WALSNDSTATE_STARTUP);
 
 	/* Get out of COPY mode (CommandComplete). */
-	EndCommand("COPY 0", DestRemote);
+	SetQueryCompletion(&qc, CMDTAG_COPY, 0);
+	EndCommand(&qc, DestRemote, false);
 }
 
 /*
@@ -1464,6 +1469,7 @@ exec_replication_command(const char *cmd_string)
 	Node	   *cmd_node;
 	MemoryContext cmd_context;
 	MemoryContext old_context;
+	QueryCompletion qc;
 
 	/*
 	 * If WAL sender has been told that shutdown is getting close, switch its
@@ -1614,7 +1620,8 @@ exec_replication_command(const char *cmd_string)
 	MemoryContextDelete(cmd_context);
 
 	/* Send CommandComplete message */
-	EndCommand("SELECT", DestRemote);
+	SetQueryCompletion(&qc, CMDTAG_SELECT, 0);
+	EndCommand(&qc, DestRemote, true);
 
 	/* Report to pgstat that this process is now idle */
 	pgstat_report_activity(STATE_IDLE, NULL);
@@ -2867,8 +2874,11 @@ WalSndDone(WalSndSendDataCallback send_data)
 	if (WalSndCaughtUp && sentPtr == replicatedPtr &&
 		!pq_is_send_pending())
 	{
+		QueryCompletion qc;
+
 		/* Inform the standby that XLOG streaming is done */
-		EndCommand("COPY 0", DestRemote);
+		SetQueryCompletion(&qc, CMDTAG_COPY, 0);
+		EndCommand(&qc, DestRemote, false);
 		pq_flush();
 
 		proc_exit(0);