From: Andrey Rachitskiy Date: Mon, 3 Aug 2026 02:15:00 +0500 Subject: [PATCH v2] Fix reachable "impossible case" in SP-GiST quad tree The fuzzy point comparisons used by getQuadrant() are not mutually exhaustive near some power-of-two boundaries. Fall back to exact comparisons when none of the existing quadrant tests match, keeping the documented axis tie-breaking. Leave the elog for NaN. Author: Ayush Tiwari Reviewed-by: Andrey Rachitskiy Reported-by: Michael Malis Discussion: https://postgr.es/m/19597-39c532e61d78dff6@postgresql.org Backpatch-through: 14 --- diff --git a/src/backend/access/spgist/spgquadtreeproc.c b/src/backend/access/spgist/spgquadtreeproc.c index 946dabc4527..2e8610f5740 100644 --- a/src/backend/access/spgist/spgquadtreeproc.c +++ b/src/backend/access/spgist/spgquadtreeproc.c @@ -52,6 +52,11 @@ spg_quad_config(PG_FUNCTION_ARGS) * * Points on one of the axes are taken to lie in the lowest-numbered * adjacent quadrant. + * + * We normally use the fuzzy point_* operators, but those are not always + * decisive (see FPeq/FPlt/FPgt). If no arm matches, fall back to exact + * comparisons with the same axis rule as above. NaN still reaches the + * error below; cleaning that up is a separate matter. */ static int16 getQuadrant(Point *centroid, Point *tst) @@ -76,6 +81,17 @@ getQuadrant(Point *centroid, Point *tst) SPTEST(point_left, tst, centroid)) return 4; + /* + * Fuzzy comparisons can leave gaps for finite values. Fall back to + * exact comparisons with the same axis tie-breaking as above. + */ + if (tst->y > centroid->y) + return (tst->x >= centroid->x) ? 1 : 4; + if (tst->y < centroid->y) + return (tst->x >= centroid->x) ? 2 : 3; + if (tst->y == centroid->y) + return (tst->x >= centroid->x) ? 1 : 3; + elog(ERROR, "getQuadrant: impossible case"); return 0; } diff --git a/src/test/regress/expected/spgist.out b/src/test/regress/expected/spgist.out index 2e911285600..1ec57562484 100644 --- a/src/test/regress/expected/spgist.out +++ b/src/test/regress/expected/spgist.out @@ -94,3 +94,18 @@ select box(point(i,j)) from generate_series(1,100,5) i, generate_series(1,10,5) j; -- leave this table around, to help in testing dump/restore +-- Check getQuadrant with large coords near a power-of-two boundary (bug #19597) +create table spgist_quad_fp_tbl(p point); +insert into spgist_quad_fp_tbl + select point(17179869183.999998, 17179869183.999998) + from generate_series(1, 4000); +create index spgist_quad_fp_idx on spgist_quad_fp_tbl using spgist(p); +insert into spgist_quad_fp_tbl + select point(17179869184.0, 17179869184.0) + from generate_series(1, 400); +select count(*) from spgist_quad_fp_tbl where p ~= point(17179869184.0, 17179869184.0); + count +------- + 400 +(1 row) + diff --git a/src/test/regress/sql/spgist.sql b/src/test/regress/sql/spgist.sql index 4828ede68c3..f89f879e3a9 100644 --- a/src/test/regress/sql/spgist.sql +++ b/src/test/regress/sql/spgist.sql @@ -89,3 +89,13 @@ select box(point(i,j)) from generate_series(1,100,5) i, generate_series(1,10,5) j; -- leave this table around, to help in testing dump/restore +-- Check getQuadrant with large coords near a power-of-two boundary (bug #19597) +create table spgist_quad_fp_tbl(p point); +insert into spgist_quad_fp_tbl + select point(17179869183.999998, 17179869183.999998) + from generate_series(1, 4000); +create index spgist_quad_fp_idx on spgist_quad_fp_tbl using spgist(p); +insert into spgist_quad_fp_tbl + select point(17179869184.0, 17179869184.0) + from generate_series(1, 400); +select count(*) from spgist_quad_fp_tbl where p ~= point(17179869184.0, 17179869184.0); -- 2.43.0