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Make EXPLAIN better at displaying MRR/BKA:

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- "Using MRR" is no longer shown with range access.
- Instead, both range and BKA accesses will show one of the following:
  = "Rowid-ordered scan"
  = "Key-ordered scan"
  = "Key-ordered Rowid-ordered scan"
depending on whether DS-MRR implementation will do scan keys in order, rowids in order,
or both.
- The patch also introduces a way for other storage engines/MRR implementations to
  pass information to EXPLAIN output about the properties of employed MRR scans.
This commit is contained in:
Sergey Petrunya
2011-04-02 14:04:45 +04:00
parent 886d84d6d1
commit 997445bc8e
46 changed files with 624 additions and 467 deletions
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mysql-test/r/merge.result
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@@ -673,7 +673,7 @@ id select_type table type possible_keys key key_len ref rows Extra
EXPLAIN SELECT * FROM t1 WHERE fileset_id = 2
AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range PRIMARY,files PRIMARY 35 NULL 5 Using index condition; Using MRR
1 SIMPLE t1 range PRIMARY,files PRIMARY 35 NULL 5 Using index condition; Rowid-ordered scan
EXPLAIN SELECT * FROM t2 WHERE fileset_id = 2
AND file_code = '0000000115' LIMIT 1;
id select_type table type possible_keys key key_len ref rows Extra