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Backport to 2.29.x: #10322: Disable direct compress when RETURNING clause references system columns #10331

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Merged
timescale-automation merged 1 commit into from
Jul 27, 2026
Merged

Backport to 2.29.x: #10322: Disable direct compress when RETURNING clause references system columns #10331

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30 changes: 30 additions & 0 deletions src/nodes/modify_hypertable.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,11 @@
*/

#include <postgres.h>
#include <access/sysattr.h>
#include <nodes/execnodes.h>
#include <nodes/makefuncs.h>
#include <nodes/nodeFuncs.h>
#include <optimizer/optimizer.h>
#include <parser/parsetree.h>
#include <utils/snapmgr.h>

Expand Down Expand Up @@ -69,6 +71,34 @@ should_use_direct_compress(ModifyHypertableState *state)
return false;
}

/*
* Direct compress stores the tuple in compressed form instead of a
* regular heap tuple, so system columns like ctid or xmin never get a
* meaningful value. Fall back to the normal insert path when RETURNING
* references them. tableoid is fine because the returning projection
* sets it explicitly.
*/
ModifyTable *mt = castNode(ModifyTable, mtstate->ps.plan);
if (mt->returningLists)
{
Bitmapset *attnos = NULL;
pull_varattnos((Node *) linitial(mt->returningLists),
resultRelInfo->ri_RangeTableIndex,
&attnos);
int attno = -1;
while ((attno = bms_next_member(attnos, attno)) >= 0)
{
AttrNumber sysattno = attno + FirstLowInvalidHeapAttributeNumber;
if (sysattno < 0 && sysattno != TableOidAttributeNumber)
{
ereport(WARNING,
(errmsg("disabling direct compress because the RETURNING clause "
"references system columns")));
return false;
}
}
}

Plan *subplan = mtstate->ps.plan->lefttree;
if (subplan->plan_rows < 10)
{
Expand Down
102 changes: 101 additions & 1 deletion tsl/test/expected/direct_compress_insert.out
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Original file line number Diff line number Diff line change
Expand Up @@ -997,11 +997,111 @@ SELECT count(*), min(label), max(label) FROM inserted;
-------+-------+------
20 | d0:10 | d1:9

-- RETURNING a system column falls back to the normal insert path, except
-- tableoid which the returning projection sets explicitly.
EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING ctid;
WARNING: disabling direct compress because the RETURNING clause references system columns
--- QUERY PLAN ---
Custom Scan (ModifyHypertable)
Direct Compress: false
-> Insert on dc_ret
-> Function Scan on generate_series i

EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING xmin;
WARNING: disabling direct compress because the RETURNING clause references system columns
--- QUERY PLAN ---
Custom Scan (ModifyHypertable)
Direct Compress: false
-> Insert on dc_ret
-> Function Scan on generate_series i

EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING cmin;
WARNING: disabling direct compress because the RETURNING clause references system columns
--- QUERY PLAN ---
Custom Scan (ModifyHypertable)
Direct Compress: false
-> Insert on dc_ret
-> Function Scan on generate_series i

EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING xmax;
WARNING: disabling direct compress because the RETURNING clause references system columns
--- QUERY PLAN ---
Custom Scan (ModifyHypertable)
Direct Compress: false
-> Insert on dc_ret
-> Function Scan on generate_series i

EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING cmax;
WARNING: disabling direct compress because the RETURNING clause references system columns
--- QUERY PLAN ---
Custom Scan (ModifyHypertable)
Direct Compress: false
-> Insert on dc_ret
-> Function Scan on generate_series i

-- tableoid stays on the direct compress path
EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING tableoid;
--- QUERY PLAN ---
Custom Scan (ModifyHypertable)
Direct Compress: true
-> Insert on dc_ret
-> Function Scan on generate_series i

-- ctid falls back and returns real tuple ids
WITH inserted AS (
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 day'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING ctid AS c, val
)
SELECT count(*), bool_and(c IS NOT NULL), min(val), max(val) FROM inserted;
WARNING: disabling direct compress because the RETURNING clause references system columns
count | bool_and | min | max
-------+----------+-----+-----
20 | t | 1 | 20

-- tableoid on the direct compress path holds the target chunk (all 20 rows
-- land in one chunk, so every RETURNING row reports the same chunk)
INSERT INTO dc_ret SELECT '2025-06-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING tableoid::regclass AS chunk;
chunk
------------------------------------------
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk
_timescaledb_internal._hyper_16_67_chunk

-- rows were actually inserted
SELECT count(*) FROM dc_ret;
count
-------
40
80

RESET timescaledb.enable_direct_compress_insert;
DROP TABLE dc_ret;
31 changes: 31 additions & 0 deletions tsl/test/sql/direct_compress_insert.sql
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Original file line number Diff line number Diff line change
Expand Up @@ -590,6 +590,37 @@ WITH inserted AS (
FROM generate_series(1, 20) i RETURNING device || ':' || val AS label
)
SELECT count(*), min(label), max(label) FROM inserted;
-- RETURNING a system column falls back to the normal insert path, except
-- tableoid which the returning projection sets explicitly.
EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING ctid;
EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING xmin;
EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING cmin;
EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING xmax;
EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING cmax;
-- tableoid stays on the direct compress path
EXPLAIN (COSTS OFF, SUMMARY OFF, TIMING OFF)
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING tableoid;
-- ctid falls back and returns real tuple ids
WITH inserted AS (
INSERT INTO dc_ret SELECT '2025-01-01'::timestamptz + (i * INTERVAL '1 day'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING ctid AS c, val
)
SELECT count(*), bool_and(c IS NOT NULL), min(val), max(val) FROM inserted;
-- tableoid on the direct compress path holds the target chunk (all 20 rows
-- land in one chunk, so every RETURNING row reports the same chunk)
INSERT INTO dc_ret SELECT '2025-06-01'::timestamptz + (i * INTERVAL '1 minute'), 'd' || (i % 2)::text, i
FROM generate_series(1, 20) i RETURNING tableoid::regclass AS chunk;
-- rows were actually inserted
SELECT count(*) FROM dc_ret;
RESET timescaledb.enable_direct_compress_insert;
Expand Down
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