Add test coverage for the LIMIT/OFFSET push-down.

FDW-131, Vaibhav Dalvi, reviewed by Sravan Velagandula, tested by
Kashif Zeeshan

Makefile

@@ -26,7 +26,7 @@ OBJS = connection.o option.o mongo_wrapper_meta.o mongo_fdw.o mongo_query.o depa
 EXTENSION = mongo_fdw
 DATA = mongo_fdw--1.0.sql  mongo_fdw--1.1.sql mongo_fdw--1.0--1.1.sql
 
-REGRESS = server_options connection_validation dml select pushdown join_pushdown aggregate_pushdown
+REGRESS = server_options connection_validation dml select pushdown join_pushdown aggregate_pushdown limit_offset_pushdown
 REGRESS_OPTS = --load-extension=$(EXTENSION)
 
 #

Makefile.meta

@@ -26,7 +26,7 @@ OBJS = connection.o option.o mongo_wrapper_meta.o mongo_fdw.o mongo_query.o depa
 EXTENSION = mongo_fdw
 DATA = mongo_fdw--1.0.sql  mongo_fdw--1.1.sql mongo_fdw--1.0--1.1.sql
 
-REGRESS = server_options connection_validation dml select pushdown join_pushdown aggregate_pushdown
+REGRESS = server_options connection_validation dml select pushdown join_pushdown aggregate_pushdown limit_offset_pushdown
 REGRESS_OPTS = --load-extension=$(EXTENSION)
 
 #

expected/aggregate_pushdown.out

@@ -1436,6 +1436,155 @@ SELECT a32, sum(a32) FROM f_test_large GROUP BY
  132 | 132
 (3 rows)
 
+-- FDW-131: Limit and offset pushdown with Aggregate pushdown.
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1;
+ min | c1 
+-----+----
+  10 | 10
+  20 | 20
+  30 | 30
+  40 | 40
+  50 | 50
+     |   
+(6 rows)
+
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT 1 OFFSET 1;
+                                QUERY PLAN                                 
+---------------------------------------------------------------------------
+ Foreign Scan
+   Output: (min(c1)), c1
+   Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(3 rows)
+
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT 1 OFFSET 1;
+ min | c1 
+-----+----
+  10 | 10
+(1 row)
+
+-- Limit 0, Offset 0 with aggregates.
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT 0 OFFSET 0;
+                                QUERY PLAN                                 
+---------------------------------------------------------------------------
+ Foreign Scan
+   Output: (min(c1)), c1
+   Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(3 rows)
+
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT 0 OFFSET 0;
+ min | c1 
+-----+----
+(0 rows)
+
+-- Limit NULL
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT NULL OFFSET 2;
+                                QUERY PLAN                                 
+---------------------------------------------------------------------------
+ Foreign Scan
+   Output: (min(c1)), c1
+   Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(3 rows)
+
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT NULL OFFSET 2;
+ min | c1 
+-----+----
+  20 | 20
+  30 | 30
+  40 | 40
+  50 | 50
+(4 rows)
+
+-- Limit ALL
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT ALL OFFSET 2;
+                                QUERY PLAN                                 
+---------------------------------------------------------------------------
+ Foreign Scan
+   Output: (min(c1)), c1
+   Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(3 rows)
+
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT ALL OFFSET 2;
+ min | c1 
+-----+----
+  20 | 20
+  30 | 30
+  40 | 40
+  50 | 50
+(4 rows)
+
+-- Limit with -ve value. Shouldn't pushdown.
+EXPLAIN (VERBOSE, COSTS FALSE)
+SELECT c1, max(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY 1 ASC NULLS FIRST LIMIT -1;
+                          QUERY PLAN                          
+--------------------------------------------------------------
+ Limit
+   Output: c1, (max(c1))
+   ->  GroupAggregate
+         Output: c1, max(c1)
+         Group Key: fdw137_t2.c1
+         ->  Foreign Scan on public.fdw137_t2
+               Output: _id, c1, c2, c3
+               Foreign Namespace: mongo_fdw_regress.test_tbl2
+(8 rows)
+
+-- Should throw an error.
+SELECT c1, max(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY 1 ASC NULLS FIRST LIMIT -1;
+ERROR:  LIMIT must not be negative
+-- Offset with -ve value. Shouldn't pushdown.
+EXPLAIN (VERBOSE, COSTS FALSE)
+SELECT c1, max(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY 1 ASC NULLS FIRST OFFSET -2;
+                                   QUERY PLAN                                    
+---------------------------------------------------------------------------------
+ Limit
+   Output: c1, (max(c1))
+   ->  Foreign Scan
+         Output: c1, (max(c1))
+         Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(5 rows)
+
+-- Should throw an error.
+SELECT c1, max(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY 1 ASC NULLS FIRST OFFSET -2;
+ERROR:  OFFSET must not be negative
+-- Limit/Offset with -ve value. Shouldn't pushdown.
+EXPLAIN (VERBOSE, COSTS FALSE)
+SELECT c1, avg(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT -1 OFFSET -2;
+                          QUERY PLAN                          
+--------------------------------------------------------------
+ Limit
+   Output: c1, (avg(c1))
+   ->  GroupAggregate
+         Output: c1, avg(c1)
+         Group Key: fdw137_t2.c1
+         ->  Foreign Scan on public.fdw137_t2
+               Output: _id, c1, c2, c3
+               Foreign Namespace: mongo_fdw_regress.test_tbl2
+(8 rows)
+
+-- Should throw an error.
+SELECT c1, avg(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT -1 OFFSET -2;
+ERROR:  OFFSET must not be negative
+-- Limit with expression evaluating to -ve value.
+EXPLAIN (VERBOSE, COSTS FALSE)
+SELECT c1, avg(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT (1 - (SELECT COUNT(*) FROM fdw137_t2));
+                                    QUERY PLAN                                     
+-----------------------------------------------------------------------------------
+ Limit
+   Output: fdw137_t2.c1, (avg(fdw137_t2.c1))
+   InitPlan 1 (returns $0)
+     ->  Foreign Scan
+           Output: (count(*))
+           Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+   ->  Foreign Scan
+         Output: fdw137_t2.c1, (avg(fdw137_t2.c1))
+         Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(9 rows)
+
+SELECT c1, avg(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT (1 - (SELECT COUNT(*) FROM fdw137_t2));
+ERROR:  LIMIT must not be negative
 -- Cleanup
 DELETE FROM fdw137_t1 WHERE c8 IS NULL;
 DELETE FROM fdw137_t1 WHERE c8 = 60;

expected/aggregate_pushdown_1.out

@@ -1436,6 +1436,155 @@ SELECT a32, sum(a32) FROM f_test_large GROUP BY
  132 | 132
 (3 rows)
 
+-- FDW-131: Limit and offset pushdown with Aggregate pushdown.
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1;
+ min | c1 
+-----+----
+  10 | 10
+  20 | 20
+  30 | 30
+  40 | 40
+  50 | 50
+     |   
+(6 rows)
+
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT 1 OFFSET 1;
+                                QUERY PLAN                                 
+---------------------------------------------------------------------------
+ Foreign Scan
+   Output: (min(c1)), c1
+   Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(3 rows)
+
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT 1 OFFSET 1;
+ min | c1 
+-----+----
+  10 | 10
+(1 row)
+
+-- Limit 0, Offset 0 with aggregates.
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT 0 OFFSET 0;
+                                QUERY PLAN                                 
+---------------------------------------------------------------------------
+ Foreign Scan
+   Output: (min(c1)), c1
+   Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(3 rows)
+
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT 0 OFFSET 0;
+ min | c1 
+-----+----
+(0 rows)
+
+-- Limit NULL
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT NULL OFFSET 2;
+                                QUERY PLAN                                 
+---------------------------------------------------------------------------
+ Foreign Scan
+   Output: (min(c1)), c1
+   Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(3 rows)
+
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT NULL OFFSET 2;
+ min | c1 
+-----+----
+  20 | 20
+  30 | 30
+  40 | 40
+  50 | 50
+(4 rows)
+
+-- Limit ALL
+EXPLAIN (VERBOSE, COSTS OFF)
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT ALL OFFSET 2;
+                                QUERY PLAN                                 
+---------------------------------------------------------------------------
+ Foreign Scan
+   Output: (min(c1)), c1
+   Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(3 rows)
+
+SELECT min(c1), c1 FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT ALL OFFSET 2;
+ min | c1 
+-----+----
+  20 | 20
+  30 | 30
+  40 | 40
+  50 | 50
+(4 rows)
+
+-- Limit with -ve value. Shouldn't pushdown.
+EXPLAIN (VERBOSE, COSTS FALSE)
+SELECT c1, max(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY 1 ASC NULLS FIRST LIMIT -1;
+                          QUERY PLAN                          
+--------------------------------------------------------------
+ Limit
+   Output: c1, (max(c1))
+   ->  GroupAggregate
+         Output: c1, max(c1)
+         Group Key: fdw137_t2.c1
+         ->  Foreign Scan on public.fdw137_t2
+               Output: _id, c1, c2, c3
+               Foreign Namespace: mongo_fdw_regress.test_tbl2
+(8 rows)
+
+-- Should throw an error.
+SELECT c1, max(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY 1 ASC NULLS FIRST LIMIT -1;
+ERROR:  LIMIT must not be negative
+-- Offset with -ve value. Shouldn't pushdown.
+EXPLAIN (VERBOSE, COSTS FALSE)
+SELECT c1, max(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY 1 ASC NULLS FIRST OFFSET -2;
+                                   QUERY PLAN                                    
+---------------------------------------------------------------------------------
+ Limit
+   Output: c1, (max(c1))
+   ->  Foreign Scan
+         Output: c1, (max(c1))
+         Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(5 rows)
+
+-- Should throw an error.
+SELECT c1, max(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY 1 ASC NULLS FIRST OFFSET -2;
+ERROR:  OFFSET must not be negative
+-- Limit/Offset with -ve value. Shouldn't pushdown.
+EXPLAIN (VERBOSE, COSTS FALSE)
+SELECT c1, avg(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT -1 OFFSET -2;
+                          QUERY PLAN                          
+--------------------------------------------------------------
+ Limit
+   Output: c1, (avg(c1))
+   ->  GroupAggregate
+         Output: c1, avg(c1)
+         Group Key: fdw137_t2.c1
+         ->  Foreign Scan on public.fdw137_t2
+               Output: _id, c1, c2, c3
+               Foreign Namespace: mongo_fdw_regress.test_tbl2
+(8 rows)
+
+-- Should throw an error.
+SELECT c1, avg(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT -1 OFFSET -2;
+ERROR:  OFFSET must not be negative
+-- Limit with expression evaluating to -ve value.
+EXPLAIN (VERBOSE, COSTS FALSE)
+SELECT c1, avg(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT (1 - (SELECT COUNT(*) FROM fdw137_t2));
+                                    QUERY PLAN                                     
+-----------------------------------------------------------------------------------
+ Limit
+   Output: fdw137_t2.c1, (avg(fdw137_t2.c1))
+   InitPlan 1 (returns $0)
+     ->  Foreign Scan
+           Output: (count(*))
+           Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+   ->  Foreign Scan
+         Output: fdw137_t2.c1, (avg(fdw137_t2.c1))
+         Foreign Namespace: Aggregate on (mongo_fdw_regress.test_tbl2 fdw137_t2)
+(9 rows)
+
+SELECT c1, avg(c1) FROM fdw137_t2 GROUP BY c1 ORDER BY c1 ASC NULLS FIRST LIMIT (1 - (SELECT COUNT(*) FROM fdw137_t2));
+ERROR:  LIMIT must not be negative
 -- Cleanup
 DELETE FROM fdw137_t1 WHERE c8 IS NULL;
 DELETE FROM fdw137_t1 WHERE c8 = 60;