Expose the estimation of number of changed tuples since last analyze

This value, now pg_stat_all_tables.n_mod_since_analyze, was already
tracked and used by autovacuum, but not exposed to the user.

Mark Kirkwood, review by Laurenz Albe

doc/src/sgml/monitoring.sgml

@@ -950,6 +950,11 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      <entry><type>bigint</></entry>
      <entry>Estimated number of dead rows</entry>
     </row>
+    <row>
+     <entry><structfield>n_mod_since_analyze</></entry>
+     <entry><type>bigint</></entry>
+     <entry>Estimated number of rows modified since this table was last analyzed</entry>
+    </row>
     <row>
      <entry><structfield>last_vacuum</></entry>
      <entry><type>timestamp with time zone</></entry>

src/backend/catalog/system_views.sql

@@ -405,6 +405,7 @@ CREATE VIEW pg_stat_all_tables AS
             pg_stat_get_tuples_hot_updated(C.oid) AS n_tup_hot_upd,
             pg_stat_get_live_tuples(C.oid) AS n_live_tup,
             pg_stat_get_dead_tuples(C.oid) AS n_dead_tup,
+            pg_stat_get_mod_since_analyze(C.oid) AS n_mod_since_analyze,
             pg_stat_get_last_vacuum_time(C.oid) as last_vacuum,
             pg_stat_get_last_autovacuum_time(C.oid) as last_autovacuum,
             pg_stat_get_last_analyze_time(C.oid) as last_analyze,

src/backend/utils/adt/pgstatfuncs.c

@@ -34,6 +34,7 @@ extern Datum pg_stat_get_tuples_deleted(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_tuples_hot_updated(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_live_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_dead_tuples(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_mod_since_analyze(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_hit(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS);
@@ -265,6 +266,22 @@ pg_stat_get_dead_tuples(PG_FUNCTION_ARGS)
 }
 
 
+Datum
+pg_stat_get_mod_since_analyze(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_StatTabEntry *tabentry;
+
+	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
+		result = 0;
+	else
+		result = (int64) (tabentry->changes_since_analyze);
+
+	PG_RETURN_INT64(result);
+}
+
+
 Datum
 pg_stat_get_blocks_fetched(PG_FUNCTION_ARGS)
 {

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201307031
+#define CATALOG_VERSION_NO	201307051
 
 #endif

src/include/catalog/pg_proc.h

@@ -2593,6 +2593,8 @@ DATA(insert OID = 2878 (  pg_stat_get_live_tuples	PGNSP PGUID 12 1 0 0 0 f f f f
 DESCR("statistics: number of live tuples");
 DATA(insert OID = 2879 (  pg_stat_get_dead_tuples	PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_dead_tuples _null_ _null_ _null_ ));
 DESCR("statistics: number of dead tuples");
+DATA(insert OID = 3177 (  pg_stat_get_mod_since_analyze	PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_mod_since_analyze _null_ _null_ _null_ ));
+DESCR("statistics: number of tuples changed since last analyze");
 DATA(insert OID = 1934 (  pg_stat_get_blocks_fetched	PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_blocks_fetched _null_ _null_ _null_ ));
 DESCR("statistics: number of blocks fetched");
 DATA(insert OID = 1935 (  pg_stat_get_blocks_hit		PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_blocks_hit _null_ _null_ _null_ ));

src/test/regress/expected/rules.out

@@ -1626,6 +1626,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
                                  |     pg_stat_get_tuples_hot_updated(c.oid) AS n_tup_hot_upd,                                                                                                                                                    +
                                  |     pg_stat_get_live_tuples(c.oid) AS n_live_tup,                                                                                                                                                              +
                                  |     pg_stat_get_dead_tuples(c.oid) AS n_dead_tup,                                                                                                                                                              +
+                                 |     pg_stat_get_mod_since_analyze(c.oid) AS n_mod_since_analyze,                                                                                                                                               +
                                  |     pg_stat_get_last_vacuum_time(c.oid) AS last_vacuum,                                                                                                                                                        +
                                  |     pg_stat_get_last_autovacuum_time(c.oid) AS last_autovacuum,                                                                                                                                                +
                                  |     pg_stat_get_last_analyze_time(c.oid) AS last_analyze,                                                                                                                                                      +
@@ -1720,6 +1721,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
                                  |     pg_stat_all_tables.n_tup_hot_upd,                                                                                                                                                                          +
                                  |     pg_stat_all_tables.n_live_tup,                                                                                                                                                                             +
                                  |     pg_stat_all_tables.n_dead_tup,                                                                                                                                                                             +
+                                 |     pg_stat_all_tables.n_mod_since_analyze,                                                                                                                                                                    +
                                  |     pg_stat_all_tables.last_vacuum,                                                                                                                                                                            +
                                  |     pg_stat_all_tables.last_autovacuum,                                                                                                                                                                        +
                                  |     pg_stat_all_tables.last_analyze,                                                                                                                                                                           +
@@ -1762,6 +1764,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
                                  |     pg_stat_all_tables.n_tup_hot_upd,                                                                                                                                                                          +
                                  |     pg_stat_all_tables.n_live_tup,                                                                                                                                                                             +
                                  |     pg_stat_all_tables.n_dead_tup,                                                                                                                                                                             +
+                                 |     pg_stat_all_tables.n_mod_since_analyze,                                                                                                                                                                    +
                                  |     pg_stat_all_tables.last_vacuum,                                                                                                                                                                            +
                                  |     pg_stat_all_tables.last_autovacuum,                                                                                                                                                                        +
                                  |     pg_stat_all_tables.last_analyze,                                                                                                                                                                           +