Details
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Bug
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Status: Open (View Workflow)
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Minor
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Resolution: Unresolved
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5.3.12, 5.5.36, 10.0.11
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None
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None
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Description
The following testcase produces incorrect EXPLAIN output ("Using MRR" is missing). This is probably a long-known problem of wrong output of EXPLAIN .. ORDER BY. I am filing it, because 1) we now have SHOW EXPLAIN (and so, potential to fix it) and 2) it is also fixed in mysql-5.6
create table ten (a int); |
insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); |
create table one_k (a int); |
insert into one_k select A.a + 10*B.a + 100*C.a from ten A, ten B, ten C; |
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create table t1 (a int, b int, c int, filler blob); |
insert into t1 select a,a,a, 'filler-data' from test.one_k; |
alter table t1 add key(a,b); |
explain select * from t1 force index(a) where a < 10000 order by b limit 10; |
select * from t1 force index(a) where a < 10000 order by b limit 10; |
set optimizer_switch='mrr_cost_based=off'; |