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Merged
serprex merged 1 commit into from
Jul 1, 2026
Merged

Disable MinMaxAgg without impacting overall query planner costs #310

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6 changes: 5 additions & 1 deletion CHANGELOG.md
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Expand Up @@ -56,6 +56,8 @@ All notable changes to this project will be documented in this file. It uses the
over floats. Aggregates with an internal transition state (anything over
`numeric`, `avg(bigint)`, `avg(interval)`) still fall back to local
aggregation. Requires `enable_partitionwise_aggregate` ([#298]).
* Disabled remote MIN/MAX optimization by raising `MinMaxAggPath` cost
rather than understating foreign scan cost ([#310]).

### 🐞 Bug Fixes

Expand Down Expand Up @@ -103,8 +105,10 @@ All notable changes to this project will be documented in this file. It uses the
"ClickHouse/pg_clickhouse#303 Flush buffered data during binary insert"
[#307]: https://github.com/ClickHouse/pg_clickhouse/pull/307
"ClickHouse/pg_clickhouse#307 Push down three-argument trim functions"
[#307]: https://github.com/ClickHouse/pg_clickhouse/pull/309
[#309]: https://github.com/ClickHouse/pg_clickhouse/pull/309
"ClickHouse/pg_clickhouse#309 add binary support to clickhouse_raw_query, add clickhouse_query"
[#310]: https://github.com/ClickHouse/pg_clickhouse/pull/310
"ClickHouse/pg_clickhouse#310 Disable MinMaxAgg without impacting overall query planner costs"

## [v0.3.2] — 2026-06-16

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17 changes: 16 additions & 1 deletion src/fdw.c
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Expand Up @@ -1799,7 +1799,7 @@ estimate_path_cost_size(
*p_rows = 1000;
*p_width = 32;
*p_startup_cost = 1.0;
*p_total_cost = 0.1 + coef;
*p_total_cost = 5.0 + coef;
}

/*
Expand Down Expand Up @@ -2927,6 +2927,7 @@ add_foreign_grouping_paths(
CHFdwRelationInfo* ifpinfo = input_rel->fdw_private;
CHFdwRelationInfo* fpinfo = grouped_rel->fdw_private;
ForeignPath* grouppath;
ListCell* lc;
double rows;
int width;
Cost startup_cost;
Expand Down Expand Up @@ -3009,6 +3010,20 @@ add_foreign_grouping_paths(
); /* no fdw_private */
#endif

/*
* For simple min/max queries Postgres adds MinMaxAggPath that rewrites as
* ORDER BY col LIMIT 1. LIMIT is invisible to FDW, causing full remote
* scan, so increase the cost to prevent this optimization.
*/
foreach (lc, grouped_rel->pathlist) {
Path* path = (Path*)lfirst(lc);

if (IsA(path, MinMaxAggPath)) {
path->startup_cost += disable_cost;
path->total_cost += disable_cost;
}
}

/* Add generated path into grouped_rel by add_path(). */
add_path(grouped_rel, (Path*)grouppath);
}
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6 changes: 3 additions & 3 deletions test/expected/binary_queries.out
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Expand Up @@ -298,9 +298,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=32)
-> Unique (cost=1.00..5.60 rows=1000 width=32)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=32)
-> Unique (cost=1.00..10.50 rows=1000 width=32)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

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6 changes: 3 additions & 3 deletions test/expected/binary_queries_1.out
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Expand Up @@ -298,9 +298,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=32)
-> Unique (cost=1.00..5.60 rows=1000 width=32)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=32)
-> Unique (cost=1.00..10.50 rows=1000 width=32)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

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6 changes: 3 additions & 3 deletions test/expected/binary_queries_2.out
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Expand Up @@ -298,9 +298,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=8)
-> Unique (cost=1.00..5.60 rows=1000 width=8)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=8)
-> Unique (cost=1.00..10.50 rows=1000 width=8)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

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6 changes: 3 additions & 3 deletions test/expected/binary_queries_3.out
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Expand Up @@ -298,9 +298,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=8)
-> Unique (cost=1.00..5.60 rows=1000 width=8)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=8)
-> Unique (cost=1.00..10.50 rows=1000 width=8)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

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6 changes: 3 additions & 3 deletions test/expected/binary_queries_4.out
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Expand Up @@ -298,9 +298,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=8)
-> Unique (cost=1.00..5.60 rows=1000 width=8)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=8)
-> Unique (cost=1.00..10.50 rows=1000 width=8)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

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6 changes: 3 additions & 3 deletions test/expected/binary_queries_5.out
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Expand Up @@ -298,9 +298,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=32)
-> Unique (cost=1.00..5.60 rows=1000 width=32)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=32)
-> Unique (cost=1.00..10.50 rows=1000 width=32)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

Expand Down
6 changes: 3 additions & 3 deletions test/expected/binary_queries_6.out
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Expand Up @@ -298,9 +298,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=32)
-> Unique (cost=1.00..5.60 rows=1000 width=32)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=32)
-> Unique (cost=1.00..10.50 rows=1000 width=32)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

Expand Down
8 changes: 4 additions & 4 deletions test/expected/http.out
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Expand Up @@ -195,7 +195,7 @@ INSERT INTO ftcopy VALUES
EXPLAIN (VERBOSE) SELECT * FROM ftcopy ORDER BY c1;
QUERY PLAN
---------------------------------------------------------------------------------------------
Foreign Scan on public.ftcopy (cost=1.00..0.60 rows=1000 width=64)
Foreign Scan on public.ftcopy (cost=1.00..5.50 rows=1000 width=64)
Output: c1, c2, c3, c4, c5, c6
Remote SQL: SELECT c1, c2, c3, c4, c5, c6 FROM http_test.tcopy ORDER BY c1 ASC NULLS LAST
(3 rows)
Expand Down Expand Up @@ -408,9 +408,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=32)
-> Unique (cost=1.00..5.60 rows=1000 width=32)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=32)
-> Unique (cost=1.00..10.50 rows=1000 width=32)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

Expand Down
8 changes: 4 additions & 4 deletions test/expected/http_1.out
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Expand Up @@ -195,7 +195,7 @@ INSERT INTO ftcopy VALUES
EXPLAIN (VERBOSE) SELECT * FROM ftcopy ORDER BY c1;
QUERY PLAN
---------------------------------------------------------------------------------------------
Foreign Scan on public.ftcopy (cost=1.00..0.60 rows=1000 width=64)
Foreign Scan on public.ftcopy (cost=1.00..5.50 rows=1000 width=64)
Output: c1, c2, c3, c4, c5, c6
Remote SQL: SELECT c1, c2, c3, c4, c5, c6 FROM http_test.tcopy ORDER BY c1 ASC NULLS LAST
(3 rows)
Expand Down Expand Up @@ -408,9 +408,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=32)
-> Unique (cost=1.00..5.60 rows=1000 width=32)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=32)
-> Unique (cost=1.00..10.50 rows=1000 width=32)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

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8 changes: 4 additions & 4 deletions test/expected/http_2.out
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Expand Up @@ -195,7 +195,7 @@ INSERT INTO ftcopy VALUES
EXPLAIN (VERBOSE) SELECT * FROM ftcopy ORDER BY c1;
QUERY PLAN
---------------------------------------------------------------------------------------------
Foreign Scan on public.ftcopy (cost=1.00..0.60 rows=1000 width=64)
Foreign Scan on public.ftcopy (cost=1.00..5.50 rows=1000 width=64)
Output: c1, c2, c3, c4, c5, c6
Remote SQL: SELECT c1, c2, c3, c4, c5, c6 FROM http_test.tcopy ORDER BY c1 ASC NULLS LAST
(3 rows)
Expand Down Expand Up @@ -408,9 +408,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=8)
-> Unique (cost=1.00..5.60 rows=1000 width=8)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=8)
-> Unique (cost=1.00..10.50 rows=1000 width=8)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

Expand Down
8 changes: 4 additions & 4 deletions test/expected/http_3.out
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Expand Up @@ -195,7 +195,7 @@ INSERT INTO ftcopy VALUES
EXPLAIN (VERBOSE) SELECT * FROM ftcopy ORDER BY c1;
QUERY PLAN
---------------------------------------------------------------------------------------------
Foreign Scan on public.ftcopy (cost=1.00..0.60 rows=1000 width=64)
Foreign Scan on public.ftcopy (cost=1.00..5.50 rows=1000 width=64)
Output: c1, c2, c3, c4, c5, c6
Remote SQL: SELECT c1, c2, c3, c4, c5, c6 FROM http_test.tcopy ORDER BY c1 ASC NULLS LAST
(3 rows)
Expand Down Expand Up @@ -408,9 +408,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=8)
-> Unique (cost=1.00..5.60 rows=1000 width=8)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=8)
-> Unique (cost=1.00..10.50 rows=1000 width=8)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

Expand Down
8 changes: 4 additions & 4 deletions test/expected/http_4.out
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Expand Up @@ -195,7 +195,7 @@ INSERT INTO ftcopy VALUES
EXPLAIN (VERBOSE) SELECT * FROM ftcopy ORDER BY c1;
QUERY PLAN
---------------------------------------------------------------------------------------------
Foreign Scan on public.ftcopy (cost=1.00..0.60 rows=1000 width=64)
Foreign Scan on public.ftcopy (cost=1.00..5.50 rows=1000 width=64)
Output: c1, c2, c3, c4, c5, c6
Remote SQL: SELECT c1, c2, c3, c4, c5, c6 FROM http_test.tcopy ORDER BY c1 ASC NULLS LAST
(3 rows)
Expand Down Expand Up @@ -408,9 +408,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=8)
-> Unique (cost=1.00..5.60 rows=1000 width=8)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=8)
-> Unique (cost=1.00..10.50 rows=1000 width=8)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

Expand Down
8 changes: 4 additions & 4 deletions test/expected/http_5.out
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Original file line number Diff line number Diff line change
Expand Up @@ -195,7 +195,7 @@ INSERT INTO ftcopy VALUES
EXPLAIN (VERBOSE) SELECT * FROM ftcopy ORDER BY c1;
QUERY PLAN
---------------------------------------------------------------------------------------------
Foreign Scan on public.ftcopy (cost=1.00..0.60 rows=1000 width=64)
Foreign Scan on public.ftcopy (cost=1.00..5.50 rows=1000 width=64)
Output: c1, c2, c3, c4, c5, c6
Remote SQL: SELECT c1, c2, c3, c4, c5, c6 FROM http_test.tcopy ORDER BY c1 ASC NULLS LAST
(3 rows)
Expand Down Expand Up @@ -408,9 +408,9 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON
EXPLAIN SELECT DISTINCT t1.c1, t2.c1 FROM ft2 t1 LEFT JOIN ft1 t2 ON (t1.c1 = t2.c1) order by t1.c1 LIMIT 10;
QUERY PLAN
----------------------------------------------------------------
Limit (cost=1.00..1.05 rows=10 width=32)
-> Unique (cost=1.00..5.60 rows=1000 width=32)
-> Foreign Scan (cost=1.00..0.60 rows=1000 width=32)
Limit (cost=1.00..1.09 rows=10 width=32)
-> Unique (cost=1.00..10.50 rows=1000 width=32)
-> Foreign Scan (cost=1.00..5.50 rows=1000 width=32)
Relations: (ft2 t1) LEFT JOIN (ft1 t2)
(4 rows)

Expand Down
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