Re: issue about range optimization

27/12/2007, 13h36

Hi,

On Dec 26, 2007 9:23 PM, 232160563 <232160563@qq.com> wrote:
> i can not understand sentences as following:
>
> For a BTREE index, an interval might be usable for conditions combined with AND, where each condition compares a key part with a constant value using =, <=>, IS NULL, >, <, >=, <=, !=,<>, BETWEEN, or LIKE 'pattern' (where 'pattern' does not start with a wildcard). An interval can be used as long as it is possible to determine a single key tuple containing all records that match the condition (or two intervals if <> or != is used).
>
> especially the second sentence :
>
> An interval can be used as long as it is possible to determine a single key tuple containing all records that match the condition (or two intervals if <> or != is used).
> (7.2.5.2. Range Access Method for Multiple-Part Indexes in the manual of mysql)
>
> the example showed in the manual is :
>
> key_part1 = 'foo' AND key_part2 >= 10 AND key_part3 > 10
>
> The single interval is

'foo', 10, 10)< (key_part1, key_part2, key_part3)< ('foo', +inf, +inf)
>
> It is possible that the created interval contains more records than the initial condition. For example,the preceding interval includes the value ('foo', 11, 0), which does not satisfy the original condition.

You should file a bug report against the documentation, then.

Cheers
Baron

27/12/2007, 13h36	#1
Baron Schwartz Messages: n/a Hébergeur:	Re: issue about range optimization Hi, On Dec 26, 2007 9:23 PM, 232160563 <232160563@qq.com> wrote: > i can not understand sentences as following: > > For a BTREE index, an interval might be usable for conditions combined with AND, where each condition compares a key part with a constant value using =, <=>, IS NULL, >, <, >=, <=, !=,<>, BETWEEN, or LIKE 'pattern' (where 'pattern' does not start with a wildcard). An interval can be used as long as it is possible to determine a single key tuple containing all records that match the condition (or two intervals if <> or != is used). > > especially the second sentence : > > An interval can be used as long as it is possible to determine a single key tuple containing all records that match the condition (or two intervals if <> or != is used). > (7.2.5.2. Range Access Method for Multiple-Part Indexes in the manual of mysql) > > the example showed in the manual is : > > key_part1 = 'foo' AND key_part2 >= 10 AND key_part3 > 10 > > The single interval is'foo', 10, 10)< (key_part1, key_part2, key_part3)< ('foo', +inf, +inf) > > It is possible that the created interval contains more records than the initial condition. For example,the preceding interval includes the value ('foo', 11, 0), which does not satisfy the original condition. You should file a bug report against the documentation, then. Cheers Baron

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