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Precise read time estimates for index_merge/Unique

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2003-12-18 06:08:00 +03:00
parent 211bc24063
commit 7dbdedcb72
13 changed files with 606 additions and 212 deletions
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20
sql/mysql_priv.h
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@@ -118,6 +118,26 @@ extern CHARSET_INFO *national_charset_info, *table_alias_charset;
*/
#define TIME_FOR_COMPARE 5 // 5 compares == one read
/*
Number of comparisons of table rowids equivalent to reading one row from a
table.
*/
#define TIME_FOR_COMPARE_ROWID (TIME_FOR_COMPARE*2)
/*
For sequential disk seeks the cost formula is:
DISK_SEEK_BASE_COST + DISK_SEEK_PROP_COST * #blocks_to_skip
The cost of average seek
DISK_SEEK_BASE_COST + DISK_SEEK_PROP_COST*BLOCKS_IN_AVG_SEEK =1.0.
*/
#define DISK_SEEK_BASE_COST ((double)0.5)
#define BLOCKS_IN_AVG_SEEK 128
#define DISK_SEEK_PROP_COST ((double)0.5/BLOCKS_IN_AVG_SEEK)
/*
Number of rows in a reference table when refereed through a not unique key.
This value is only used when we don't know anything about the key