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

1 files changed, 6 insertions, 8 deletions

diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index cc02cf824ed..3a5676fb39e 100644
--- a/src/backend/commands/createas.c
+++ b/src/backend/commands/createas.c
@@ -10,7 +10,7 @@
  *
  * Formerly, CTAS was implemented as a variant of SELECT, which led
  * to assorted legacy behaviors that we still try to preserve, notably that
- * we must return a tuples-processed count in the completionTag.  (We no
+ * we must return a tuples-processed count in the QueryCompletion.  (We no
  * longer do that for CTAS ... WITH NO DATA, however.)
  *
  * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
@@ -225,7 +225,7 @@ create_ctas_nodata(List *tlist, IntoClause *into)
 ObjectAddress
 ExecCreateTableAs(ParseState *pstate, CreateTableAsStmt *stmt,
 				  ParamListInfo params, QueryEnvironment *queryEnv,
-				  char *completionTag)
+				  QueryCompletion *qc)
 {
 	Query	   *query = castNode(Query, stmt->query);
 	IntoClause *into = stmt->into;
@@ -270,7 +270,7 @@ ExecCreateTableAs(ParseState *pstate, CreateTableAsStmt *stmt,
 		ExecuteStmt *estmt = castNode(ExecuteStmt, query->utilityStmt);
 
 		Assert(!is_matview);	/* excluded by syntax */
-		ExecuteQuery(pstate, estmt, into, params, dest, completionTag);
+		ExecuteQuery(pstate, estmt, into, params, dest, qc);
 
 		/* get object address that intorel_startup saved for us */
 		address = ((DR_intorel *) dest)->reladdr;
@@ -352,11 +352,9 @@ ExecCreateTableAs(ParseState *pstate, CreateTableAsStmt *stmt,
 		/* run the plan to completion */
 		ExecutorRun(queryDesc, ForwardScanDirection, 0L, true);
 
-		/* save the rowcount if we're given a completionTag to fill */
-		if (completionTag)
-			snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
-					 "SELECT " UINT64_FORMAT,
-					 queryDesc->estate->es_processed);
+		/* save the rowcount if we're given a qc to fill */
+		if (qc)
+			SetQueryCompletion(qc, CMDTAG_SELECT, queryDesc->estate->es_processed);
 
 		/* get object address that intorel_startup saved for us */
 		address = ((DR_intorel *) dest)->reladdr;