feat: command_tag_format GUC with legacy/modern/verbose/fqn modes

Adds a new enum GUC command_tag_format (PGC_USERSET) with four modes:
- legacy: INSERT 0 N (default, backward compatible)
- modern: INSERT N (drops legacy OID field)
- verbose: INSERT tablename N (shows relation name)
- fqn: INSERT schema.tablename N (fully qualified)

Tested output:
  legacy:  INSERT 0 1
  modern:  INSERT 1
  verbose: INSERT users 1
  fqn:     INSERT myschema.users 1

Supports SET LOCAL for per-transaction control.
libpq PQcmdTuples() handles all formats gracefully.

Note: verbose/fqn currently only populated for INSERT (UPDATE/DELETE
show count only — relname propagation for those pending).

Author: NikolayS

src/backend/tcop/cmdtag.c

@@ -14,6 +14,7 @@
 #include "postgres.h"
 
 #include "tcop/cmdtag.h"
+#include "utils/guc.h"
 #include "utils/builtins.h"
 
 
@@ -36,11 +37,16 @@ static const CommandTagBehavior tag_behavior[] = {
 
 #undef PG_CMDTAG
 
+/* GUC variable: command tag format style */
+int		command_tag_format = COMMAND_TAG_FORMAT_LEGACY;
+
 void
 InitializeQueryCompletion(QueryCompletion *qc)
 {
 	qc->commandTag = CMDTAG_UNKNOWN;
 	qc->nprocessed = 0;
+	qc->relname = NULL;
+	qc->nspname = NULL;
 }
 
 const char *
@@ -147,8 +153,33 @@ BuildQueryCompletionString(char *buff, const QueryCompletion *qc,
 	{
 		if (tag == CMDTAG_INSERT)
 		{
-			*bufp++ = ' ';
-			*bufp++ = '0';
+			if (command_tag_format == COMMAND_TAG_FORMAT_LEGACY)
+			{
+				/* Legacy: INSERT 0 N */
+				*bufp++ = ' ';
+				*bufp++ = '0';
+			}
+			else if ((command_tag_format == COMMAND_TAG_FORMAT_VERBOSE ||
+					  command_tag_format == COMMAND_TAG_FORMAT_FQN) &&
+					 qc->relname != NULL)
+			{
+				/* Verbose/FQN: INSERT [schema.]table N */
+				*bufp++ = ' ';
+				if (command_tag_format == COMMAND_TAG_FORMAT_FQN &&
+					qc->nspname != NULL)
+				{
+					Size nsplen = strlen(qc->nspname);
+					memcpy(bufp, qc->nspname, nsplen);
+					bufp += nsplen;
+					*bufp++ = '.';
+				}
+				{
+					Size rellen = strlen(qc->relname);
+					memcpy(bufp, qc->relname, rellen);
+					bufp += rellen;
+				}
+			}
+			/* Modern: INSERT N (nothing extra before count) */
 		}
 		*bufp++ = ' ';
 		bufp += pg_ulltoa_n(qc->nprocessed, bufp);

src/backend/tcop/pquery.c

@@ -26,6 +26,9 @@
 #include "tcop/pquery.h"
 #include "tcop/utility.h"
 #include "utils/memutils.h"
+#include "catalog/namespace.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
 #include "utils/snapmgr.h"
 
 
@@ -181,6 +184,27 @@ ProcessQuery(PlannedStmt *plan,
 			tag = CMDTAG_UNKNOWN;
 
 		SetQueryCompletion(qc, tag, queryDesc->estate->es_processed);
+
+		/* For verbose/FQN command tags, attach relation info for DML */
+		if (command_tag_format >= COMMAND_TAG_FORMAT_VERBOSE &&
+			(tag == CMDTAG_INSERT || tag == CMDTAG_UPDATE ||
+			 tag == CMDTAG_DELETE || tag == CMDTAG_MERGE) &&
+			queryDesc->plannedstmt != NULL &&
+			queryDesc->plannedstmt->resultRelations != NIL &&
+			queryDesc->estate->es_result_relations != NULL)
+		{
+			int ri_index = linitial_int(queryDesc->plannedstmt->resultRelations) - 1;
+			if (ri_index >= 0 &&
+				ri_index < (int) queryDesc->estate->es_range_table_size &&
+				queryDesc->estate->es_result_relations[ri_index] != NULL &&
+				queryDesc->estate->es_result_relations[ri_index]->ri_RelationDesc != NULL)
+			{
+				ResultRelInfo *rri = queryDesc->estate->es_result_relations[ri_index];
+				qc->relname = RelationGetRelationName(rri->ri_RelationDesc);
+				qc->nspname = get_namespace_name(
+					RelationGetNamespace(rri->ri_RelationDesc));
+			}
+		}
 	}
 
 	/*

src/backend/utils/misc/guc_parameters.dat

@@ -426,6 +426,7 @@
   options => 'client_message_level_options',
 },
 
+
 { name => 'cluster_name', type => 'string', context => 'PGC_POSTMASTER', group => 'PROCESS_TITLE',
   short_desc => 'Sets the name of the cluster, which is included in the process title.',
   flags => 'GUC_IS_NAME',
@@ -435,6 +436,15 @@
 },
 
 # we have no microseconds designation, so can't supply units here
+
+{ name => 'command_tag_format', type => 'enum', context => 'PGC_USERSET', group => 'CLIENT_CONN_STATEMENT',
+  short_desc => 'Controls the format of INSERT command completion tags.',
+  long_desc => 'legacy: INSERT 0 N (default, backward compatible). modern: INSERT N (no OID). verbose: INSERT tablename N. fqn: INSERT schema.tablename N.',
+  variable => 'command_tag_format',
+  boot_val => 'COMMAND_TAG_FORMAT_LEGACY',
+  options => 'command_tag_format_options',
+  includes => 'tcop/cmdtag.h',
+},
 { name => 'commit_delay', type => 'int', context => 'PGC_SUSET', group => 'WAL_SETTINGS',
   short_desc => 'Sets the delay in microseconds between transaction commit and flushing WAL to disk.',
   variable => 'CommitDelay',

src/backend/utils/misc/guc_tables.c

@@ -19,6 +19,7 @@
  *--------------------------------------------------------------------
  */
 #include "postgres.h"
+#include "tcop/cmdtag.h"
 
 #ifdef HAVE_COPYFILE_H
 #include <copyfile.h>
@@ -148,6 +149,14 @@ static const struct config_enum_entry client_message_level_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry command_tag_format_options[] = {
+	{"legacy", 0, false},
+	{"modern", 1, false},
+	{"verbose", 2, false},
+	{"fqn", 3, false},
+	{NULL, 0, false}
+};
+
 const struct config_enum_entry server_message_level_options[] = {
 	{"debug5", DEBUG5, false},
 	{"debug4", DEBUG4, false},

src/include/tcop/cmdtag.h

@@ -30,6 +30,8 @@ typedef struct QueryCompletion
 {
 	CommandTag	commandTag;
 	uint64		nprocessed;
+	const char *relname;		/* relation name for verbose command tags */
+	const char *nspname;		/* schema name for FQN command tags */
 } QueryCompletion;
 
 
@@ -56,6 +58,14 @@ extern bool command_tag_display_rowcount(CommandTag commandTag);
 extern bool command_tag_event_trigger_ok(CommandTag commandTag);
 extern bool command_tag_table_rewrite_ok(CommandTag commandTag);
 extern CommandTag GetCommandTagEnum(const char *commandname);
+
+/* GUC: command tag format style */
+#define COMMAND_TAG_FORMAT_LEGACY   0   /* INSERT 0 N (default, backward compat) */
+#define COMMAND_TAG_FORMAT_MODERN   1   /* INSERT N (no OID) */
+#define COMMAND_TAG_FORMAT_VERBOSE  2   /* INSERT tablename N */
+#define COMMAND_TAG_FORMAT_FQN      3   /* INSERT schema.tablename N */
+
+extern int command_tag_format;
 extern Size BuildQueryCompletionString(char *buff, const QueryCompletion *qc,
 									   bool nameonly);
 

src/interfaces/libpq/fe-exec.c

@@ -3847,12 +3847,18 @@ PQcmdTuples(PGresult *res)
 	if (strncmp(res->cmdStatus, "INSERT ", 7) == 0)
 	{
 		p = res->cmdStatus + 7;
-		/* INSERT: skip oid and space */
-		while (*p && *p != ' ')
-			p++;
-		if (*p == 0)
-			goto interpret_error;	/* no space? */
-		p++;
+		/* INSERT: handle both "INSERT oid count" and "INSERT count" */
+		{
+			char *q = p;
+			while (*q && *q != ' ')
+				q++;
+			if (*q == ' ')
+			{
+				/* Old format: "INSERT oid count" - skip oid and space */
+				p = q + 1;
+			}
+			/* else: new format "INSERT count" - p already points to count */
+		}
 	}
 	else if (strncmp(res->cmdStatus, "SELECT ", 7) == 0 ||
 			 strncmp(res->cmdStatus, "DELETE ", 7) == 0 ||