mirror of https://github.com/postgres/postgres
Attempt to fix newly added Memoize regression test
Both drongo and fairywren seem not to like a new regression test added
by 2cca95e17
. These machines show a different number of actual rows in
the EXPLAIN ANALYZE output. Since the number of actual rows is divided by
the number of loops, I suspect this might be due to some platform
dependant rounding behavior as the total row count is 5 and the number of
loops is 2. drongo and fairywren seem to be calculating that 5.0 / 2.0 is
3, whereas most other machines think the answer is 2.
Here we tweak the test query's WHERE clause so it's 4.0 / 2.0 instead.
There shouldn't be too much wiggle room for platform dependant-behavior to
be a factor with those numbers.
Reported-by: Tom Lane
Discussion: https://postgr.es/m/1035225.1706301718%40sss.pgh.pa.us
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@ -96,14 +96,14 @@ WHERE t1.unique1 < 1000;
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SELECT explain_memoize('
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SELECT COUNT(*),AVG(t2.t1two) FROM tenk1 t1 LEFT JOIN
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LATERAL (
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SELECT t1.two as t1two, * FROM tenk1 t2 WHERE t2.unique1 < 5 OFFSET 0
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SELECT t1.two as t1two, * FROM tenk1 t2 WHERE t2.unique1 < 4 OFFSET 0
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) t2
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ON t1.two = t2.two
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WHERE t1.unique1 < 10;', false);
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explain_memoize
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----------------------------------------------------------------------------------------------
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Aggregate (actual rows=1 loops=N)
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-> Nested Loop Left Join (actual rows=25 loops=N)
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-> Nested Loop Left Join (actual rows=20 loops=N)
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-> Index Scan using tenk1_unique1 on tenk1 t1 (actual rows=10 loops=N)
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Index Cond: (unique1 < 10)
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-> Memoize (actual rows=2 loops=N)
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@ -113,20 +113,20 @@ WHERE t1.unique1 < 10;', false);
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-> Subquery Scan on t2 (actual rows=2 loops=N)
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Filter: (t1.two = t2.two)
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Rows Removed by Filter: 2
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-> Index Scan using tenk1_unique1 on tenk1 t2_1 (actual rows=5 loops=N)
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Index Cond: (unique1 < 5)
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-> Index Scan using tenk1_unique1 on tenk1 t2_1 (actual rows=4 loops=N)
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Index Cond: (unique1 < 4)
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(13 rows)
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-- And check we get the expected results.
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SELECT COUNT(*),AVG(t2.t1two) FROM tenk1 t1 LEFT JOIN
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LATERAL (
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SELECT t1.two as t1two, * FROM tenk1 t2 WHERE t2.unique1 < 5 OFFSET 0
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SELECT t1.two as t1two, * FROM tenk1 t2 WHERE t2.unique1 < 4 OFFSET 0
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) t2
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ON t1.two = t2.two
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WHERE t1.unique1 < 10;
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count | avg
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-------+------------------------
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25 | 0.40000000000000000000
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20 | 0.50000000000000000000
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(1 row)
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-- Reduce work_mem and hash_mem_multiplier so that we see some cache evictions
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@ -61,7 +61,7 @@ WHERE t1.unique1 < 1000;
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SELECT explain_memoize('
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SELECT COUNT(*),AVG(t2.t1two) FROM tenk1 t1 LEFT JOIN
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LATERAL (
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SELECT t1.two as t1two, * FROM tenk1 t2 WHERE t2.unique1 < 5 OFFSET 0
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SELECT t1.two as t1two, * FROM tenk1 t2 WHERE t2.unique1 < 4 OFFSET 0
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) t2
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ON t1.two = t2.two
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WHERE t1.unique1 < 10;', false);
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@ -69,7 +69,7 @@ WHERE t1.unique1 < 10;', false);
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-- And check we get the expected results.
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SELECT COUNT(*),AVG(t2.t1two) FROM tenk1 t1 LEFT JOIN
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LATERAL (
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SELECT t1.two as t1two, * FROM tenk1 t2 WHERE t2.unique1 < 5 OFFSET 0
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SELECT t1.two as t1two, * FROM tenk1 t2 WHERE t2.unique1 < 4 OFFSET 0
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) t2
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ON t1.two = t2.two
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WHERE t1.unique1 < 10;
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