From: Tomas Vondra Date: Fri, 27 Oct 2023 15:56:27 +0000 (+0200) Subject: Fix overflow when calculating timestamp distance in BRIN X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=b5489b75c6ce9517ab5f9d6f1d98bc928f6d5bd5;p=users%2Frhaas%2Fpostgres.git Fix overflow when calculating timestamp distance in BRIN When calculating distances for timestamp values for BRIN minmax-multi indexes, we need to be careful about overflows for extreme values. If the value overflows into a negative value, the index may be inefficient. The new regression test checks this for the timestamp type by adding a table with enough values to force range compaction/merging. The values are close to min/max, which means a risk of overflow. Fixed by converting the int64 values to double first, before calculating the distance. This prevents the overflow. We may lose some precision, of course, but that's good enough. In the worst case we build a slightly less efficient index, but for large distances this won't matter. This only affects minmax-multi indexes on timestamp columns, with ranges containing values sufficiently distant to cause an overflow. That seems like a fairly rare case in practice. Backpatch to 14, where minmax-multi indexes were introduced. Reported-by: Ashutosh Bapat Reviewed-by: Ashutosh Bapat, Dean Rasheed Backpatch-through: 14 Discussion: https://postgr.es/m/eef0ea8c-4aaa-8d0d-027f-58b1f35dd170@enterprisedb.com --- diff --git a/src/backend/access/brin/brin_minmax_multi.c b/src/backend/access/brin/brin_minmax_multi.c index f8b2a3f9bc..8c72a0a036 100644 --- a/src/backend/access/brin/brin_minmax_multi.c +++ b/src/backend/access/brin/brin_minmax_multi.c @@ -2144,7 +2144,7 @@ brin_minmax_multi_distance_timestamp(PG_FUNCTION_ARGS) if (TIMESTAMP_NOT_FINITE(dt1) || TIMESTAMP_NOT_FINITE(dt2)) PG_RETURN_FLOAT8(0); - delta = dt2 - dt1; + delta = (float8) dt2 - (float8) dt1; Assert(delta >= 0); diff --git a/src/test/regress/expected/brin_multi.out b/src/test/regress/expected/brin_multi.out index 9f46934c9b..c18d9764c1 100644 --- a/src/test/regress/expected/brin_multi.out +++ b/src/test/regress/expected/brin_multi.out @@ -823,3 +823,18 @@ SELECT COUNT(*) FROM brin_test_multi_2 WHERE a = 'aab32389-22bc-c25a-6f60-6eb525 DROP TABLE brin_test_multi_2; RESET enable_seqscan; +-- test overflows during CREATE INDEX with extreme timestamp values +CREATE TABLE brin_timestamp_test(a TIMESTAMPTZ); +SET datestyle TO iso; +-- values close to timetamp minimum +INSERT INTO brin_timestamp_test +SELECT '4713-01-01 00:00:01 BC'::timestamptz + (i || ' seconds')::interval + FROM generate_series(1,30) s(i); +-- values close to timetamp maximum +INSERT INTO brin_timestamp_test +SELECT '294276-12-01 00:00:01'::timestamptz + (i || ' seconds')::interval + FROM generate_series(1,30) s(i); +CREATE INDEX ON brin_timestamp_test USING brin (a timestamptz_minmax_multi_ops) WITH (pages_per_range=1); +DROP TABLE brin_timestamp_test; +RESET enable_seqscan; +RESET datestyle; diff --git a/src/test/regress/sql/brin_multi.sql b/src/test/regress/sql/brin_multi.sql index d50dbdee68..847bb5aa01 100644 --- a/src/test/regress/sql/brin_multi.sql +++ b/src/test/regress/sql/brin_multi.sql @@ -586,3 +586,24 @@ SELECT COUNT(*) FROM brin_test_multi_2 WHERE a = 'aab32389-22bc-c25a-6f60-6eb525 DROP TABLE brin_test_multi_2; RESET enable_seqscan; + +-- test overflows during CREATE INDEX with extreme timestamp values +CREATE TABLE brin_timestamp_test(a TIMESTAMPTZ); + +SET datestyle TO iso; + +-- values close to timetamp minimum +INSERT INTO brin_timestamp_test +SELECT '4713-01-01 00:00:01 BC'::timestamptz + (i || ' seconds')::interval + FROM generate_series(1,30) s(i); + +-- values close to timetamp maximum +INSERT INTO brin_timestamp_test +SELECT '294276-12-01 00:00:01'::timestamptz + (i || ' seconds')::interval + FROM generate_series(1,30) s(i); + +CREATE INDEX ON brin_timestamp_test USING brin (a timestamptz_minmax_multi_ops) WITH (pages_per_range=1); +DROP TABLE brin_timestamp_test; + +RESET enable_seqscan; +RESET datestyle;