postgres
diff --git a/‎contrib/postgres_fdw/deparse.c
Lines changed: 4 additions & 3 deletions b/‎contrib/postgres_fdw/deparse.c
Lines changed: 4 additions & 3 deletions
diff --git a/‎contrib/postgres_fdw/postgres_fdw.c
Lines changed: 42 additions & 18 deletions b/‎contrib/postgres_fdw/postgres_fdw.c
Lines changed: 42 additions & 18 deletions
diff --git a/‎contrib/postgres_fdw/postgres_fdw.h
Lines changed: 1 addition & 1 deletion b/‎contrib/postgres_fdw/postgres_fdw.h
Lines changed: 1 addition & 1 deletion
@@ -2368,22 +2368,23 @@ deparseAnalyzeSizeSql(StringInfo buf, Relation rel)
 }
 
 /*
- * Construct SELECT statement to acquire the number of rows of a relation.
+ * Construct SELECT statement to acquire the number of rows and the relkind of
+ * a relation.
  *
  * Note: we just return the remote server's reltuples value, which might
  * be off a good deal, but it doesn't seem worth working harder.  See
  * comments in postgresAcquireSampleRowsFunc.
  */
 void
-deparseAnalyzeTuplesSql(StringInfo buf, Relation rel)
+deparseAnalyzeInfoSql(StringInfo buf, Relation rel)
 {
 	StringInfoData relname;
 
 	/* We'll need the remote relation name as a literal. */
 	initStringInfo(&relname);
 	deparseRelation(&relname, rel);
 
-	appendStringInfoString(buf, "SELECT reltuples FROM pg_catalog.pg_class WHERE oid = ");
+	appendStringInfoString(buf, "SELECT reltuples, relkind FROM pg_catalog.pg_class WHERE oid = ");
 	deparseStringLiteral(buf, relname.data);
 	appendStringInfoString(buf, "::pg_catalog.regclass");
 }
 
@@ -4974,18 +4974,25 @@ postgresAnalyzeForeignTable(Relation relation,
 }
 
 /*
- * postgresCountTuplesForForeignTable
+ * postgresGetAnalyzeInfoForForeignTable
  *		Count tuples in foreign table (just get pg_class.reltuples).
+ *
+ * can_tablesample determines if the remote relation supports acquiring the
+ * sample using TABLESAMPLE.
  */
 static double
-postgresCountTuplesForForeignTable(Relation relation)
+postgresGetAnalyzeInfoForForeignTable(Relation relation, bool *can_tablesample)
 {
 	ForeignTable *table;
 	UserMapping *user;
 	PGconn	   *conn;
 	StringInfoData sql;
 	PGresult   *volatile res = NULL;
 	volatile double reltuples = -1;
+	volatile char relkind = 0;
+
+	/* assume the remote relation does not support TABLESAMPLE */
+	*can_tablesample = false;
 
 	/*
 	 * Get the connection to use.  We do the remote access as the table's
@@ -4999,7 +5006,7 @@ postgresCountTuplesForForeignTable(Relation relation)
 	 * Construct command to get page count for relation.
 	 */
 	initStringInfo(&sql);
-	deparseAnalyzeTuplesSql(&sql, relation);
+	deparseAnalyzeInfoSql(&sql, relation);
 
 	/* In what follows, do not risk leaking any PGresults. */
 	PG_TRY();
@@ -5008,9 +5015,10 @@ postgresCountTuplesForForeignTable(Relation relation)
 		if (PQresultStatus(res) != PGRES_TUPLES_OK)
 			pgfdw_report_error(ERROR, res, conn, false, sql.data);
 
-		if (PQntuples(res) != 1 || PQnfields(res) != 1)
+		if (PQntuples(res) != 1 || PQnfields(res) != 2)
 			elog(ERROR, "unexpected result from deparseAnalyzeTuplesSql query");
 		reltuples = strtod(PQgetvalue(res, 0, 0), NULL);
+		relkind = *(PQgetvalue(res, 0, 1));
 	}
 	PG_FINALLY();
 	{
@@ -5021,6 +5029,11 @@ postgresCountTuplesForForeignTable(Relation relation)
 
 	ReleaseConnection(conn);
 
+	/* TABLESAMPLE is supported only for regular tables and matviews */
+	*can_tablesample = (relkind == RELKIND_RELATION ||
+						relkind == RELKIND_MATVIEW ||
+						relkind == RELKIND_PARTITIONED_TABLE);
+
 	return reltuples;
 }
 
@@ -5147,27 +5160,25 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("remote server does not support TABLESAMPLE feature")));
 
-	/*
-	 * For "auto" method, pick the one we believe is best. For servers with
-	 * TABLESAMPLE support we pick BERNOULLI, for old servers we fall-back to
-	 * random() to at least reduce network transfer.
-	 */
-	if (method == ANALYZE_SAMPLE_AUTO)
-	{
-		if (server_version_num < 95000)
-			method = ANALYZE_SAMPLE_RANDOM;
-		else
-			method = ANALYZE_SAMPLE_BERNOULLI;
-	}
-
 	/*
 	 * If we've decided to do remote sampling, calculate the sampling rate. We
 	 * need to get the number of tuples from the remote server, but skip that
 	 * network round-trip if not needed.
 	 */
 	if (method != ANALYZE_SAMPLE_OFF)
 	{
-		reltuples = postgresCountTuplesForForeignTable(relation);
+		bool	can_tablesample;
+
+		reltuples = postgresGetAnalyzeInfoForForeignTable(relation,
+														  &can_tablesample);
+
+		/*
+		 * Make sure we're not choosing TABLESAMPLE when the remote relation does
+		 * not support that. But only do this for "auto" - if the user explicitly
+		 * requested BERNOULLI/SYSTEM, it's better to fail.
+		 */
+		if (!can_tablesample && (method == ANALYZE_SAMPLE_AUTO))
+			method = ANALYZE_SAMPLE_RANDOM;
 
 		/*
 		 * Remote's reltuples could be 0 or -1 if the table has never been
@@ -5212,6 +5223,19 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 		}
 	}
 
+	/*
+	 * For "auto" method, pick the one we believe is best. For servers with
+	 * TABLESAMPLE support we pick BERNOULLI, for old servers we fall-back to
+	 * random() to at least reduce network transfer.
+	 */
+	if (method == ANALYZE_SAMPLE_AUTO)
+	{
+		if (server_version_num < 95000)
+			method = ANALYZE_SAMPLE_RANDOM;
+		else
+			method = ANALYZE_SAMPLE_BERNOULLI;
+	}
+
 	/*
 	 * Construct cursor that retrieves whole rows from remote.
 	 */
 
@@ -223,7 +223,7 @@ extern void deparseDirectDeleteSql(StringInfo buf, PlannerInfo *root,
 								   List *returningList,
 								   List **retrieved_attrs);
 extern void deparseAnalyzeSizeSql(StringInfo buf, Relation rel);
-extern void deparseAnalyzeTuplesSql(StringInfo buf, Relation rel);
+extern void deparseAnalyzeInfoSql(StringInfo buf, Relation rel);
 extern void deparseAnalyzeSql(StringInfo buf, Relation rel,
 							  PgFdwSamplingMethod sample_method,
 							  double sample_frac,