Refactor code converting a publication name List to a StringInfo

The existing get_publications_str() is renamed to GetPublicationsStr()
and is moved to pg_subscription.c, so as it is possible to reuse it at
two locations of the tablesync code where the same logic was duplicated.

fetch_remote_table_info() was doing two List->StringInfo conversions
when dealing with a server of version 15 or newer.  The conversion
happens only once now.

This refactoring leads to less code overall.

Author: Peter Smith
Reviewed-by: Michael Paquier, Masahiko Sawada
Discussion: https://postgr.es/m/CAHut+PtJMk4bKXqtpvqVy9ckknCgK9P6=FeG8zHF=6+Em_Snpw@mail.gmail.com

src/backend/catalog/pg_subscription.c

@@ -34,6 +34,37 @@
 
 static List *textarray_to_stringlist(ArrayType *textarray);
 
+/*
+ * Add a comma-separated list of publication names to the 'dest' string.
+ */
+void
+GetPublicationsStr(List *publications, StringInfo dest, bool quote_literal)
+{
+	ListCell   *lc;
+	bool		first = true;
+
+	Assert(publications != NIL);
+
+	foreach(lc, publications)
+	{
+		char	   *pubname = strVal(lfirst(lc));
+
+		if (first)
+			first = false;
+		else
+			appendStringInfoString(dest, ", ");
+
+		if (quote_literal)
+			appendStringInfoString(dest, quote_literal_cstr(pubname));
+		else
+		{
+			appendStringInfoChar(dest, '"');
+			appendStringInfoString(dest, pubname);
+			appendStringInfoChar(dest, '"');
+		}
+	}
+}
+
 /*
  * Fetch the subscription from the syscache.
  */

src/backend/commands/subscriptioncmds.c

@@ -439,37 +439,6 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 	}
 }
 
-/*
- * Add publication names from the list to a string.
- */
-static void
-get_publications_str(List *publications, StringInfo dest, bool quote_literal)
-{
-	ListCell   *lc;
-	bool		first = true;
-
-	Assert(publications != NIL);
-
-	foreach(lc, publications)
-	{
-		char	   *pubname = strVal(lfirst(lc));
-
-		if (first)
-			first = false;
-		else
-			appendStringInfoString(dest, ", ");
-
-		if (quote_literal)
-			appendStringInfoString(dest, quote_literal_cstr(pubname));
-		else
-		{
-			appendStringInfoChar(dest, '"');
-			appendStringInfoString(dest, pubname);
-			appendStringInfoChar(dest, '"');
-		}
-	}
-}
-
 /*
  * Check that the specified publications are present on the publisher.
  */
@@ -486,7 +455,7 @@ check_publications(WalReceiverConn *wrconn, List *publications)
 	appendStringInfoString(cmd, "SELECT t.pubname FROM\n"
 						   " pg_catalog.pg_publication t WHERE\n"
 						   " t.pubname IN (");
-	get_publications_str(publications, cmd, true);
+	GetPublicationsStr(publications, cmd, true);
 	appendStringInfoChar(cmd, ')');
 
 	res = walrcv_exec(wrconn, cmd->data, 1, tableRow);
@@ -523,7 +492,7 @@ check_publications(WalReceiverConn *wrconn, List *publications)
 		/* Prepare the list of non-existent publication(s) for error message. */
 		StringInfo	pubnames = makeStringInfo();
 
-		get_publications_str(publicationsCopy, pubnames, false);
+		GetPublicationsStr(publicationsCopy, pubnames, false);
 		ereport(WARNING,
 				errcode(ERRCODE_UNDEFINED_OBJECT),
 				errmsg_plural("publication %s does not exist on the publisher",
@@ -2151,7 +2120,7 @@ check_publications_origin(WalReceiverConn *wrconn, List *publications,
 						   "     JOIN pg_subscription_rel PS ON (GPT.relid = PS.srrelid),\n"
 						   "     pg_class C JOIN pg_namespace N ON (N.oid = C.relnamespace)\n"
 						   "WHERE C.oid = GPT.relid AND P.pubname IN (");
-	get_publications_str(publications, &cmd, true);
+	GetPublicationsStr(publications, &cmd, true);
 	appendStringInfoString(&cmd, ")\n");
 
 	/*
@@ -2208,7 +2177,7 @@ check_publications_origin(WalReceiverConn *wrconn, List *publications,
 		StringInfo	pubnames = makeStringInfo();
 
 		/* Prepare the list of publication(s) for warning message. */
-		get_publications_str(publist, pubnames, false);
+		GetPublicationsStr(publist, pubnames, false);
 		ereport(WARNING,
 				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				errmsg("subscription \"%s\" requested copy_data with origin = NONE but might copy data that had a different origin",
@@ -2243,17 +2212,17 @@ fetch_table_list(WalReceiverConn *wrconn, List *publications)
 	List	   *tablelist = NIL;
 	int			server_version = walrcv_server_version(wrconn);
 	bool		check_columnlist = (server_version >= 150000);
+	StringInfo	pub_names = makeStringInfo();
 
 	initStringInfo(&cmd);
 
+	/* Build the pub_names comma-separated string. */
+	GetPublicationsStr(publications, pub_names, true);
+
 	/* Get the list of tables from the publisher. */
 	if (server_version >= 160000)
 	{
-		StringInfoData pub_names;
-
 		tableRow[2] = INT2VECTOROID;
-		initStringInfo(&pub_names);
-		get_publications_str(publications, &pub_names, true);
 
 		/*
 		 * From version 16, we allowed passing multiple publications to the
@@ -2275,9 +2244,7 @@ fetch_table_list(WalReceiverConn *wrconn, List *publications)
 						 "                FROM pg_publication\n"
 						 "                WHERE pubname IN ( %s )) AS gpt\n"
 						 "             ON gpt.relid = c.oid\n",
-						 pub_names.data);
+						 pub_names->data);
-
-		pfree(pub_names.data);
 	}
 	else
 	{
@@ -2288,12 +2255,13 @@ fetch_table_list(WalReceiverConn *wrconn, List *publications)
 		if (check_columnlist)
 			appendStringInfoString(&cmd, ", t.attnames\n");
 
-		appendStringInfoString(&cmd, "FROM pg_catalog.pg_publication_tables t\n"
+		appendStringInfo(&cmd, "FROM pg_catalog.pg_publication_tables t\n"
-							   " WHERE t.pubname IN (");
+						 " WHERE t.pubname IN ( %s )",
-		get_publications_str(publications, &cmd, true);
+						 pub_names->data);
-		appendStringInfoChar(&cmd, ')');
 	}
 
+	destroyStringInfo(pub_names);
+
 	res = walrcv_exec(wrconn, cmd.data, check_columnlist ? 3 : 2, tableRow);
 	pfree(cmd.data);
 

src/backend/replication/logical/tablesync.c

@@ -802,7 +802,7 @@ fetch_remote_table_info(char *nspname, char *relname,
 	Oid			qualRow[] = {TEXTOID};
 	bool		isnull;
 	int			natt;
-	ListCell   *lc;
+	StringInfo	pub_names = NULL;
 	Bitmapset  *included_cols = NULL;
 
 	lrel->nspname = nspname;
@@ -856,15 +856,10 @@ fetch_remote_table_info(char *nspname, char *relname,
 		WalRcvExecResult *pubres;
 		TupleTableSlot *tslot;
 		Oid			attrsRow[] = {INT2VECTOROID};
-		StringInfoData pub_names;
 
-		initStringInfo(&pub_names);
+		/* Build the pub_names comma-separated string. */
-		foreach(lc, MySubscription->publications)
+		pub_names = makeStringInfo();
-		{
+		GetPublicationsStr(MySubscription->publications, pub_names, true);
-			if (foreach_current_index(lc) > 0)
-				appendStringInfoString(&pub_names, ", ");
-			appendStringInfoString(&pub_names, quote_literal_cstr(strVal(lfirst(lc))));
-		}
 
 		/*
 		 * Fetch info about column lists for the relation (from all the
@@ -881,7 +876,7 @@ fetch_remote_table_info(char *nspname, char *relname,
 						 " WHERE gpt.relid = %u AND c.oid = gpt.relid"
 						 "   AND p.pubname IN ( %s )",
 						 lrel->remoteid,
-						 pub_names.data);
+						 pub_names->data);
 
 		pubres = walrcv_exec(LogRepWorkerWalRcvConn, cmd.data,
 							 lengthof(attrsRow), attrsRow);
@@ -936,8 +931,6 @@ fetch_remote_table_info(char *nspname, char *relname,
 		ExecDropSingleTupleTableSlot(tslot);
 
 		walrcv_clear_result(pubres);
-
-		pfree(pub_names.data);
 	}
 
 	/*
@@ -1039,19 +1032,8 @@ fetch_remote_table_info(char *nspname, char *relname,
 	 */
 	if (walrcv_server_version(LogRepWorkerWalRcvConn) >= 150000)
 	{
-		StringInfoData pub_names;
+		/* Reuse the already-built pub_names. */
-
+		Assert(pub_names != NULL);
-		/* Build the pubname list. */
-		initStringInfo(&pub_names);
-		foreach_node(String, pubstr, MySubscription->publications)
-		{
-			char	   *pubname = strVal(pubstr);
-
-			if (foreach_current_index(pubstr) > 0)
-				appendStringInfoString(&pub_names, ", ");
-
-			appendStringInfoString(&pub_names, quote_literal_cstr(pubname));
-		}
 
 		/* Check for row filters. */
 		resetStringInfo(&cmd);
@@ -1062,7 +1044,7 @@ fetch_remote_table_info(char *nspname, char *relname,
 						 " WHERE gpt.relid = %u"
 						 "   AND p.pubname IN ( %s )",
 						 lrel->remoteid,
-						 pub_names.data);
+						 pub_names->data);
 
 		res = walrcv_exec(LogRepWorkerWalRcvConn, cmd.data, 1, qualRow);
 
@@ -1101,6 +1083,7 @@ fetch_remote_table_info(char *nspname, char *relname,
 		ExecDropSingleTupleTableSlot(slot);
 
 		walrcv_clear_result(res);
+		destroyStringInfo(pub_names);
 	}
 
 	pfree(cmd.data);

src/include/catalog/pg_subscription.h

@@ -20,7 +20,7 @@
 #include "access/xlogdefs.h"
 #include "catalog/genbki.h"
 #include "catalog/pg_subscription_d.h"
-
+#include "lib/stringinfo.h"
 #include "nodes/pg_list.h"
 
 /*
@@ -180,4 +180,7 @@ extern void DisableSubscription(Oid subid);
 
 extern int	CountDBSubscriptions(Oid dbid);
 
+extern void GetPublicationsStr(List *publications, StringInfo dest,
+							   bool quote_literal);
+
 #endif							/* PG_SUBSCRIPTION_H */