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Allow GiST distance function to return merely a lower-bound.

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The distance function can now set *recheck = false, like index quals. The
executor will then re-check the ORDER BY expressions, and use a queue to
reorder the results on the fly.

This makes it possible to do kNN-searches on polygons and circles, which
don't store the exact value in the index, but just a bounding box.

Alexander Korotkov and me
This commit is contained in:
Heikki Linnakangas
2015-05-15 14:26:51 +03:00
parent ecd222e770
commit 35fcb1b3d0
19 changed files with 699 additions and 40 deletions
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12
src/test/regress/sql/create_index.sql
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@@ -224,6 +224,10 @@ SELECT count(*) FROM radix_text_tbl WHERE t > 'Worth
SELECT count(*) FROM radix_text_tbl WHERE t ~>~ 'Worth St ';
SELECT * FROM gpolygon_tbl ORDER BY f1 <-> '(0,0)'::point LIMIT 10;
SELECT * FROM gcircle_tbl ORDER BY f1 <-> '(200,300)'::point LIMIT 10;
-- Now check the results from plain indexscan
SET enable_seqscan = OFF;
SET enable_indexscan = ON;
@@ -437,6 +441,14 @@ EXPLAIN (COSTS OFF)
SELECT count(*) FROM radix_text_tbl WHERE t ~>~ 'Worth St ';
SELECT count(*) FROM radix_text_tbl WHERE t ~>~ 'Worth St ';
EXPLAIN (COSTS OFF)
SELECT * FROM gpolygon_tbl ORDER BY f1 <-> '(0,0)'::point LIMIT 10;
SELECT * FROM gpolygon_tbl ORDER BY f1 <-> '(0,0)'::point LIMIT 10;
EXPLAIN (COSTS OFF)
SELECT * FROM gcircle_tbl ORDER BY f1 <-> '(200,300)'::point LIMIT 10;
SELECT * FROM gcircle_tbl ORDER BY f1 <-> '(200,300)'::point LIMIT 10;
-- Now check the results from bitmap indexscan
SET enable_seqscan = OFF;
SET enable_indexscan = OFF;