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Fixed bug mdev-4369.

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The function was adjusted to be able to aggregate
the counters of the merged elements. 
Before this change it was not possible to guarantee the correctness
of the counters passed to the the call-back parameter walk_action.
As a result, when some elements of a Unique object were flushed into
disk the function passed to merge_walk() as the call-back parameter
could return wrong counters of elements. This could lead to building
wrong histograms.
This commit is contained in:
Igor Babaev
2013-04-06 15:36:28 -07:00
parent 1c30fb2a15
commit 10f0530b22
5 changed files with 121 additions and 6 deletions
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43
mysql-test/t/statistics.test
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@ -638,5 +638,48 @@ set histogram_type=default;
drop table t1;
--echo #
--echo # Bug mdev-4369: histogram for a column with many distinct values
--echo #
CREATE TABLE t1 (id int);
CREATE TABLE t2 (id int);
INSERT INTO t1 (id) VALUES (1), (1), (1),(1);
INSERT INTO t1 (id) SELECT id FROM t1;
INSERT INTO t1 SELECT id+1 FROM t1;
INSERT INTO t1 SELECT id+2 FROM t1;
INSERT INTO t1 SELECT id+4 FROM t1;
INSERT INTO t1 SELECT id+8 FROM t1;
INSERT INTO t1 SELECT id+16 FROM t1;
INSERT INTO t1 SELECT id+32 FROM t1;
INSERT INTO t1 SELECT id+64 FROM t1;
INSERT INTO t1 SELECT id+128 FROM t1;
INSERT INTO t1 SELECT id+256 FROM t1;
INSERT INTO t1 SELECT id+512 FROM t1;
INSERT INTO t2 SELECT id FROM t1 ORDER BY id*rand();
SELECT COUNT(*) FROM t2;
SELECT COUNT(DISTINCT id) FROM t2;
set @@tmp_table_size=1024*16;
set @@max_heap_table_size=1024*16;
set histogram_size=63;
analyze table t2 persistent for all;
select db_name, table_name, column_name,
min_value, max_value,
nulls_ratio, avg_frequency,
hist_size, hist_type, HEX(histogram)
FROM mysql.column_stats;
set histogram_size=default;
drop table t1, t2;
set use_stat_tables=@save_use_stat_tables;