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fix: REINDEX reclaims the entries of deleted rows no snapshot can see (#1407) #1412

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Merged
jdatcmd merged 2 commits into from
Oct 15, 2026
Merged

fix: REINDEX reclaims the entries of deleted rows no snapshot can see (#1407) #1412

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3ecde7f
test: the grouped node's float sums raise on overflow, as core's do (…
jdatcmd Oct 15, 2026
e8a1af5
fix: REINDEX reclaims the entries of deleted rows no snapshot can see…
jdatcmd Oct 15, 2026
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4 changes: 3 additions & 1 deletion docs/limitations.md
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Expand Up @@ -779,7 +779,9 @@ therefore still be cheaper as a scan.
## Indexes

- Stale index entries left by deletes and updates are filtered on fetch and
reclaimed by `REINDEX`, not removed opportunistically.
reclaimed by `REINDEX`, not removed opportunistically. `REINDEX` keeps the entry
of a deleted row only while a transaction that began before the delete is still
running, as it does on heap.
- `CREATE INDEX CONCURRENTLY` (the concurrent validate path) and partial
block-range index builds are not supported.

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37 changes: 37 additions & 0 deletions src/columnar_reader.c
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Expand Up @@ -296,6 +296,15 @@ struct PgColumnarReadState
bool emitDeleted;
bool lastRowDeleted;

/*
* With emitDeleted, a row deleted under THIS snapshot too is dead to every
* transaction, and is not returned (#1407). The index build passes one that
* sees only transactions older than every running snapshot.
*/
Snapshot deadHorizon;
char *deadMask;
uint32 deadMaskLen;

MemoryContext readContext; /* whole scan */
MemoryContext stripeContext; /* reset per stripe */
MemoryContext groupContext; /* reset per chunk group (decompressed) */
Expand Down Expand Up @@ -2833,6 +2842,17 @@ pgcolumnar_native_load_group(PgColumnarReadState *rs)
&rs->nativeDeleteMask,
&rs->nativeDeleteMaskLen);
}
rs->deadMask = NULL;
rs->deadMaskLen = 0;
if (rs->deadHorizon != NULL && rs->nativeDeleteMask != NULL)
{
List *deadList = PgColumnarReadDeleteVectorList(rs->storageId,
rg->groupNumber,
rs->deadHorizon);

pgcolumnar_merge_delete_vectors(deadList, (uint32) ((rg->rowCount + 7) / 8),
&rs->deadMask, &rs->deadMaskLen);
}

/*
* The chunk metadata is read before the data (#338) because it carries the
Expand Down Expand Up @@ -3458,6 +3478,9 @@ pgcolumnar_native_next_row(PgColumnarReadState *rs, Datum *values, bool *nulls,

if (deleted && !rs->emitDeleted)
continue; /* row deleted: cursors advanced, do not emit */
if (deleted && rs->deadMask != NULL &&
dv_row_deleted(rs->deadMask, rs->deadMaskLen, rs->rowInGroup - 1))
continue; /* dead to every transaction: no snapshot needs it */

rs->lastRowDeleted = deleted;
return true;
Expand All @@ -3479,6 +3502,20 @@ PgColumnarReadSetEmitDeleted(PgColumnarReadState *readState, bool emit)
readState->emitDeleted = emit;
}

/*
* PgColumnarReadSetDeadHorizon
* With PgColumnarReadSetEmitDeleted, leave out the deleted rows that are
* deleted under `horizon` too (#1407). The index build passes a snapshot that
* sees only transactions older than every running snapshot, so a row deleted
* there is dead to all and needs no index entry, as heap's build skips a dead
* tuple. Without it every deleted row was indexed, and REINDEX reclaimed none.
*/
void
PgColumnarReadSetDeadHorizon(PgColumnarReadState *readState, Snapshot horizon)
{
readState->deadHorizon = horizon;
}

bool
PgColumnarReadLastRowDeleted(PgColumnarReadState *readState)
{
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1 change: 1 addition & 0 deletions src/columnar_reader.h
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Expand Up @@ -45,6 +45,7 @@ extern bool PgColumnarReadFoldColumn(PgColumnarReadState *readState, int attidx,
int16 *attlen, const uint32 **vecRawLen);

extern void PgColumnarReadSetEmitDeleted(PgColumnarReadState *readState, bool emit);
extern void PgColumnarReadSetDeadHorizon(PgColumnarReadState *readState, Snapshot horizon);
extern bool PgColumnarReadLastRowDeleted(PgColumnarReadState *readState);
extern void PgColumnarReadSetProjection(PgColumnarReadState *readState,
Bitmapset *projectedColumns);
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22 changes: 22 additions & 0 deletions src/columnar_tableam.c
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Expand Up @@ -32,6 +32,7 @@
#include "catalog/storage.h"
#include "commands/defrem.h"
#include "commands/extension.h"
#include "storage/procarray.h"
#include "commands/trigger.h"
#include "catalog/dependency.h"
#include "access/htup_details.h"
Expand Down Expand Up @@ -2419,6 +2420,8 @@ pgcolumnar_index_build_range_scan(Relation table_rel, Relation index_rel,
IndexBuildCallback callback, void *callback_state,
TableScanDesc scan)
{
SnapshotData deadHorizon;
Snapshot deadHorizonReg;
PgColumnarReadState *readState;
bool ownReadState;
Bitmapset *projected;
Expand Down Expand Up @@ -2547,6 +2550,24 @@ pgcolumnar_index_build_range_scan(Relation table_rel, Relation index_rel,
/* deleted rows too, flagged, so the build can index them as not alive (#1341) */
PgColumnarReadSetEmitDeleted(readState, true);

/*
* BUT NOT A ROW DEAD TO EVERY TRANSACTION (#1407). The horizon sees exactly the
* transactions committed before every running snapshot began, so a row deleted
* under it is one no snapshot can see, and heap's build skips the like. With
* every deleted row indexed, REINDEX -- documented as what reclaims stale
* entries -- reclaimed none: 9 rows in 10 deleted, and the rebuilt index kept
* its size where heap's shrank to a tenth. curcid 0 keeps this transaction's
* own writes out of it; a row it deleted is not dead to all anyway.
*/
memset(&deadHorizon, 0, sizeof(deadHorizon));
deadHorizon.snapshot_type = SNAPSHOT_MVCC;
deadHorizon.xmin = GetOldestNonRemovableTransactionId(table_rel);
deadHorizon.xmax = deadHorizon.xmin;
deadHorizon.curcid = FirstCommandId;
/* registered: a visibility check asserts it (PG 18+), and the copy outlives this frame */
deadHorizonReg = RegisterSnapshot(&deadHorizon);
PgColumnarReadSetDeadHorizon(readState, deadHorizonReg);

/*
* Say which branch ran and how wide the reader it produced will actually
* read, so a test can assert the projection NARROWED rather than infer it
Expand Down Expand Up @@ -2624,6 +2645,7 @@ pgcolumnar_index_build_range_scan(Relation table_rel, Relation index_rel,
*/
if (scan != NULL)
table_endscan(scan);
UnregisterSnapshot(deadHorizonReg);

return reltuples;
}
Expand Down
18 changes: 18 additions & 0 deletions test/am_contracts.sh
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Expand Up @@ -309,4 +309,22 @@ psql_run "INSERT INTO ibu VALUES (5);"
check "a unique index builds over a key whose other holder is a deleted row" \
"$(state "CREATE UNIQUE INDEX ibu_k ON ibu (k);")|$(q "SET enable_seqscan = off; SELECT count(*) FROM ibu WHERE k = 5;" | tail -1)" "ok|1"

# But only rows some snapshot can still see (#1407). Every deleted row went in, so
# REINDEX, documented as what reclaims stale entries, reclaimed none: 9 rows in 10
# deleted, and the rebuilt index kept its size where heap's shrank to a tenth.
for am in pgcolumnar heap; do
psql_run "CREATE TABLE ix_$am (a int) USING $am; INSERT INTO ix_$am SELECT g FROM generate_series(1, 100000) g;
CREATE INDEX ix_${am}_a ON ix_$am (a); DELETE FROM ix_$am WHERE a % 10 <> 0;"
done
ix_reclaim() { # ix_reclaim AM -> reclaimed, when REINDEX takes the index under half its size
local before after
before="$(q "SELECT pg_relation_size('ix_${1}_a')")"
psql_run "REINDEX INDEX ix_${1}_a;"
after="$(q "SELECT pg_relation_size('ix_${1}_a')")"
[ -n "$before" ] && [ -n "$after" ] && [ "$after" -lt $((before / 2)) ] && echo reclaimed || echo "kept:$before->$after"
}
check "REINDEX after a committed delete of most rows reclaims their entries, as heap's does" \
"$(ix_reclaim pgcolumnar)|$(ix_reclaim heap)|$(q "SET enable_seqscan = off; SELECT count(*) FROM ix_pgcolumnar WHERE a > 0;" | tail -1)" \
"reclaimed|reclaimed|10000"

pgc_summary
95 changes: 95 additions & 0 deletions test/check_ledger.tsv
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@@ -1,6 +1,7 @@
am_contracts am_contracts ON CONFLICT DO NOTHING skips the duplicate and inserts the new row 15;16;17;18;19 2026-10-14 speculative insert refused as unsupported, as before #1341
am_contracts am_contracts ON CONFLICT DO UPDATE is refused as unsupported (0A000), and changes nothing 15;16;17;18;19 2026-10-14 speculative insert refused as unsupported, as before #1341
am_contracts am_contracts ON CONFLICT DO UPDATE with no conflicting row inserts it 15;16;17;18;19 2026-10-14 speculative insert refused as unsupported, as before #1341
am_contracts am_contracts REINDEX after a committed delete of most rows reclaims their entries, as heap's does 15;16;17;18;19 2026-10-15 the index build indexing every deleted row (main before #1407's fix)
am_contracts am_contracts a DO NOTHING racing an uncommitted insert of the same key waits, then skips it 15;16;17;18;19 2026-10-14 speculative insert refused as unsupported, as before #1341
am_contracts am_contracts a TRUNCATE rolled back at transaction level restores every row 15;16;17;18;19 2026-10-14 TRUNCATE empties the old storage in place (RelationTruncate before the swap)
am_contracts am_contracts a TRUNCATE rolled back to a savepoint restores every row, and the transaction goes on 15;16;17;18;19 2026-10-14 TRUNCATE empties the old storage in place (RelationTruncate before the swap)
Expand Down Expand Up @@ -2059,6 +2060,100 @@ native_fetch_coalesce native_fetch_coalesce premise: fetching one projected colu
native_fetch_coalesce native_fetch_coalesce premise: the coalescing helper holds both the bound and the validity copy 15;16;17;18;19 never -
native_fetch_coalesce native_fetch_coalesce the validity copy is bounded by the chunk length before it runs 15;16;17;18;19 never -
native_fetch_coalesce native_fetch_coalesce the wide fetch returns the projected values 15;16;17;18;19 2026-10-14 every column of a coalesced fetch is copied from the start of the span (off = 0)
native_groupagg native_groupagg a NULL key counts as a group in the bucket bound: four groups under a cap of 3 are declined and all answered 15;16;17;18;19 never -
native_groupagg native_groupagg a cached plan run under a lower cap stops at the runtime cap, with its hint 15;16;17;18;19 never -
native_groupagg native_groupagg a date_bin key is bounded as a truncating key is 15;16;17;18;19 never -
native_groupagg native_groupagg a five-minute bucket query over more rows than the cap still takes the grouped path 15;16;17;18;19 never -
native_groupagg native_groupagg a lookalike function with the same signature gets NO bound 15;16;17;18;19 never -
native_groupagg native_groupagg a mixed timestamp/timestamptz predicate never narrows the estimate below the true count 15;16;17;18;19 never -
native_groupagg native_groupagg a non-time expression key gets no bound either 15;16;17;18;19 never -
native_groupagg native_groupagg a plain key over more rows than the cap is declined 15;16;17;18;19 never -
native_groupagg native_groupagg a skewed key whose estimate is far too low is declined under a cap of 30,000, and answers every group 15;16;17;18;19 never -
native_groupagg native_groupagg an informed estimate (plain column) is not replaced 15;16;17;18;19 never -
native_groupagg native_groupagg and a date_bin key with no time bound is bounded from the zone maps 15;16;17;18;19 never -
native_groupagg native_groupagg and it is an UPPER bound: the true group count is at or below it 15;16;17;18;19 never -
native_groupagg native_groupagg and the declined query answers what heap answers 15;16;17;18;19 never -
native_groupagg native_groupagg answer: non-deterministic collation grouping is case-insensitive (10 groups) 15;16;17;18;19 never -
native_groupagg native_groupagg avg(float8) overflow errors like core 15;16;17;18;19 never -
native_groupagg native_groupagg avg(float8) overflow: node fires 15;16;17;18;19 never -
native_groupagg native_groupagg by default a five-minute bucket query takes the grouped path 15;16;17;18;19 never -
native_groupagg native_groupagg empty table: grouped scan yields 0 rows 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY added column 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY added column [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY host 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY host [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY host after deletes 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY host after deletes [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY host, added column 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY host, added column [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY hour 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY hour [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY hour, host (q4/q5 shape) 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY hour, host (q4/q5 shape) [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY integer expr key 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY integer expr key [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY region, host (two text keys) 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY region, host (two text keys) [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY smallint column key 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: GROUP BY smallint column key [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: NULL ts group folds like heap 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: NULL ts group folds like heap [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: WHERE on measure + GROUP BY host 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: WHERE on measure + GROUP BY host [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: WHERE range + GROUP BY hour, host 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: WHERE range + GROUP BY hour, host [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: all rows filtered out -> 0 groups 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: default cap runs the high-cardinality key 15;16;17;18;19 never -
native_groupagg native_groupagg oracle exact: f(key) output still correct 15;16;17;18;19 never -
native_groupagg native_groupagg plan: GROUP BY hour expr uses grouped node 15;16;17;18;19 never -
native_groupagg native_groupagg plan: GROUP BY text key uses grouped node 15;16;17;18;19 never -
native_groupagg native_groupagg plan: GROUP BY with no aggregate falls back 15;16;17;18;19 never -
native_groupagg native_groupagg plan: f(key) output falls back 15;16;17;18;19 never -
native_groupagg native_groupagg plan: non-deterministic collation key falls back 15;16;17;18;19 never -
native_groupagg native_groupagg plan: off -> ordinary Agg, not grouped node 15;16;17;18;19 never -
native_groupagg native_groupagg plan: q4-shape (WHERE+2 keys) uses grouped node 15;16;17;18;19 never -
native_groupagg native_groupagg plan: the node is chosen for a key well under the gate 15;16;17;18;19 never -
native_groupagg native_groupagg planning a bucketed GROUP BY scans zone_map once, not once per row group 15;16;17;18;19 never -
native_groupagg native_groupagg premise: ANALYZE estimates the skewed key's 40,001 groups below 3,000 15;16;17;18;19 never -
native_groupagg native_groupagg premise: and so is ten, so the two costs are comparable 15;16;17;18;19 never -
native_groupagg native_groupagg premise: one aggregate is costed as the grouped node 15;16;17;18;19 never -
native_groupagg native_groupagg premise: the cost fixture holds the rows the 450.00 is computed from 15;16;17;18;19 never -
native_groupagg native_groupagg premise: the fixture has many row groups, so one scan and one per group differ 15;16;17;18;19 never -
native_groupagg native_groupagg premise: the grouped path is costed at all (non-empty estimate) 15;16;17;18;19 never -
native_groupagg native_groupagg premise: the mixed-type window holds data 15;16;17;18;19 never -
native_groupagg native_groupagg raising groupagg_max_groups to 10,000,000 lets the same query take the grouped path 15;16;17;18;19 never -
native_groupagg native_groupagg regress B1: sum(real) fires the node 15;16;17;18;19 never -
native_groupagg native_groupagg regress B1: sum(real) is nonzero 15;16;17;18;19 never -
native_groupagg native_groupagg regress B1: sum(real) matches heap, not 0 15;16;17;18;19 never -
native_groupagg native_groupagg regress B2: gating WHERE (SELECT false) returns no rows 15;16;17;18;19 never -
native_groupagg native_groupagg regress B2: gating WHERE (SELECT true) is a no-op 15;16;17;18;19 never -
native_groupagg native_groupagg regress B2: gating WHERE falls back (not the node) 15;16;17;18;19 never -
native_groupagg native_groupagg sum(float8) and sum(real) overflow raise 22003, as core does 15;16;17;18;19 2026-10-15 the node's float8 sum without its overflow check
native_groupagg native_groupagg sum(float8) and sum(real) overflow: node fires 15;16;17;18;19 never -
native_groupagg native_groupagg ten aggregates cost more than one (#349) 15;16;17;18;19 never -
native_groupagg native_groupagg the bound is accurate for a truncating time key, not just smaller 15;16;17;18;19 never -
native_groupagg native_groupagg the grouped path is on by default 15;16;17;18;19 never -
native_groupagg native_groupagg toggle exact: GROUP BY host 15;16;17;18;19 never -
native_groupagg native_groupagg toggle exact: GROUP BY host [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg toggle exact: GROUP BY host after deletes 15;16;17;18;19 never -
native_groupagg native_groupagg toggle exact: GROUP BY host after deletes [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg toggle exact: GROUP BY hour, host 15;16;17;18;19 never -
native_groupagg native_groupagg toggle exact: GROUP BY hour, host [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg toggle exact: GROUP BY region, host, WHERE 15;16;17;18;19 never -
native_groupagg native_groupagg toggle exact: GROUP BY region, host, WHERE [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg toggle float/avg: GROUP BY host 15;16;17;18;19 never -
native_groupagg native_groupagg toggle float/avg: GROUP BY host [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg toggle float/avg: GROUP BY hour, host 15;16;17;18;19 never -
native_groupagg native_groupagg toggle float/avg: GROUP BY hour, host [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg toggle float/avg: WHERE + GROUP BY region, host 15;16;17;18;19 never -
native_groupagg native_groupagg toggle float/avg: WHERE + GROUP BY region, host [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg toggle min/max numeric display-scale tie 15;16;17;18;19 never -
native_groupagg native_groupagg toggle min/max numeric display-scale tie [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg toggle sum signed-zero (-0 preserved) 15;16;17;18;19 never -
native_groupagg native_groupagg toggle sum signed-zero (-0 preserved) [node fires] 15;16;17;18;19 never -
native_groupagg native_groupagg while a matching-type predicate still gets one 15;16;17;18;19 never -
native_groupagg native_groupagg with no time bound at all, a truncating key is bounded from the zone maps 15;16;17;18;19 never -
native_groupagg native_groupagg with only a lower time bound, a truncating key is still bounded 15;16;17;18;19 never -
native_join_runtime_filter native_join_runtime_filter 3-table answer equals filter-off 15;16;17;18;19 2026-09-23 the runtime bloom probe's verdict inverted, so the filter rejects what matches
native_join_runtime_filter native_join_runtime_filter 3-table join order matches filter-off 15;16;17;18;19 never -
native_join_runtime_filter native_join_runtime_filter 3-table plan has coordinator 15;16;17;18;19 never -
Expand Down
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