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Fix unique constraint violation when NULLS NOT DISTINCT #10150

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Fix unique constraint violation when NULLS NOT DISTINCT #10150

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3 changes: 2 additions & 1 deletion tsl/src/compression/compression_dml.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1176,7 +1176,8 @@ decompress_batches_scan(Relation in_rel, Relation out_rel, Relation index_rel, S
*/
for (; attrno >= 0; attrno = bms_next_member(null_columns, attrno))
{
is_null_condition = is_nulls && list_nth_int(is_nulls, pos);
// We cannot filter out NULLs if the unique constraint has NULLS NOT DISTINCT
is_null_condition = (is_nulls && list_nth_int(is_nulls, pos)) || (constraints && constraints->nullsnotdistinct);
seg_col_is_null = slot_attisnull(slot, attrno);
if ((seg_col_is_null && !is_null_condition) || (!seg_col_is_null && is_null_condition))
{
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25 changes: 25 additions & 0 deletions tsl/test/shared/expected/compression_nulls_not_distinct.out
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Expand Up @@ -37,5 +37,30 @@ ERROR: duplicate key value violates unique constraint "_hyper_X_X_chunk_nulls_n
INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.5', 'd2', 'l1', 1);
INFO: Using index scan with scan keys: index 1, heap 4, memory 2.
INFO: Number of compressed rows fetched from index: 1. Number of compressed rows filtered by heap filters: 0.
-- test that this is correctly handled when using table scan
-- see https://github.com/timescale/timescaledb/issues/10057
SELECT count(compress_chunk(c)) FROM show_chunks('nulls_not_distinct') c;
INFO: Using index "compress_hyper_X_X_chunk_device__ts_meta_v2_last_time__ts_idx" for recompression
count
-------
1

set timescaledb.enable_dml_decompression_tuple_filtering to off;
-- should not insert a duplicate, conflict with existing (NULL, 'l1') row
\set ON_ERROR_STOP 0
INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.5', NULL, 'l1', 1);
INFO: Using table scan with scan keys: index 0, heap 4, memory 0.
INFO: Number of compressed rows fetched from table scan: 2. Number of compressed rows filtered: 1.
ERROR: duplicate key value violates unique constraint "_hyper_X_X_chunk_nulls_not_distinct_time_device_label_idx"
INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.5', 'd2', NULL, 1);
INFO: Using table scan with scan keys: index 0, heap 3, memory 0.
INFO: Number of compressed rows fetched from table scan: 1. Number of compressed rows filtered: 0.
ERROR: duplicate key value violates unique constraint "_hyper_X_X_chunk_nulls_not_distinct_time_device_label_idx"
\set ON_ERROR_STOP 1
-- should insert without error, no conflict
INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.15', 'd2', 'l1', 1);
INFO: Using table scan with scan keys: index 0, heap 5, memory 0.
INFO: Number of compressed rows fetched from table scan: 1. Number of compressed rows filtered: 0.
RESET timescaledb.enable_dml_decompression_tuple_filtering;
RESET timescaledb.debug_compression_path_info;
DROP TABLE nulls_not_distinct;
15 changes: 15 additions & 0 deletions tsl/test/shared/sql/compression_nulls_not_distinct.sql
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Expand Up @@ -30,5 +30,20 @@ INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.5', 'd2', NULL, 1);
-- should insert without error, no conflict
INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.5', 'd2', 'l1', 1);

-- test that this is correctly handled when using table scan
-- see https://github.com/timescale/timescaledb/issues/10057
SELECT count(compress_chunk(c)) FROM show_chunks('nulls_not_distinct') c;
set timescaledb.enable_dml_decompression_tuple_filtering to off;

@antekresic antekresic Jul 2, 2026

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This kinda feels weird. Could we add a test case where we drop the compressed chunk index and test that works correctly now as well? Reading the issue seems that also caused the issue.


-- should not insert a duplicate, conflict with existing (NULL, 'l1') row
\set ON_ERROR_STOP 0
INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.5', NULL, 'l1', 1);
INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.5', 'd2', NULL, 1);
\set ON_ERROR_STOP 1

-- should insert without error, no conflict
INSERT INTO nulls_not_distinct VALUES ('2024-01-01 0:00:00.15', 'd2', 'l1', 1);

RESET timescaledb.enable_dml_decompression_tuple_filtering;
RESET timescaledb.debug_compression_path_info;
DROP TABLE nulls_not_distinct;
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