Commit 3059b545 authored by arjen@co3064164-a.bitbike.com's avatar arjen@co3064164-a.bitbike.com
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Clarified USE/IGNORE INDEX in all relevant sections. 

Added mention of USE/IGNORE KEY as alias for USE/IGNORE INDEX.
Fixups references to this feature throughout manual.
parent 0b3ab589

Docs/manual.texi

+23 −12
Original line number Diff line number Diff line
@@ -24779,14 +24779,12 @@ and check the query with @code{EXPLAIN} again. @xref{ALTER TABLE}. 
To see what indexes a table has, use @code{SHOW INDEX FROM tbl_name}.















@item key













@findex USE INDEX













@findex IGNORE INDEX













The @code{key} column indicates the key that MySQL actually













The @code{key} column indicates the key (index) that MySQL actually















decided to use. The key is @code{NULL} if no index was chosen.  If















MySQL chooses the wrong index, you can probably force















MySQL to use another index by using @code{myisamchk --analyze},















@xref{myisamchk syntax}, or by using @code{USE INDEX/IGNORE INDEX}.













@xref{JOIN}.













@xref{SELECT}.





























@item key_len















The @code{key_len} column indicates the length of the key that










@@ -32809,16 +32807,27 @@ because the column value may not yet be determined when the













@xref{Problems with alias}.





























@item













@findex AS













@findex USE INDEX













@findex IGNORE INDEX













@findex USE KEY













@findex IGNORE KEY















The @code{FROM table_references} clause indicates the tables from which to















retrieve rows.  If you name more than one table, you are performing a















join.  For information on join syntax, see @ref{JOIN, , @code{JOIN}}.













For each table specified, you may optionally specify an alias, as well as













make a suggestion to the optimiser what index to use or ignore.













@findex USE INDEX













@findex IGNORE INDEX













For each table specified, you may optionally specify an alias.















@example















table_name [[AS] alias] [USE INDEX (key_list)] [IGNORE INDEX (key_list)]















@end example













As of MySQL Version 3.23.12, you can give hints about which













index MySQL should use when retrieving information from a













table. This is useful if @code{EXPLAIN} shows that MySQL is













using the wrong index.  By specifying @code{USE INDEX (key_list)}, you













can tell MySQL to use only one of the specified indexes to













find rows in the table.  The alternative syntax @code{IGNORE INDEX













(key_list)} can be used to tell MySQL to not use some













particular index.













@code{USE/IGNORE KEY} are synonyms for @code{USE/IGNORE INDEX}.





























@item















You can refer to a column as @code{col_name}, @code{tbl_name.col_name}, or










@@ -33108,8 +33117,7 @@ table_reference NATURAL [RIGHT [OUTER]] JOIN table_reference













@end example





























Where @code{table_reference} is defined as:













@findex USE INDEX













@findex IGNORE INDEX













@findex AS















@example















table_name [[AS] alias] [USE INDEX (key_list)] [IGNORE INDEX (key_list)]















@end example










@@ -33215,6 +33223,9 @@ can tell MySQL to use only one of the specified indexes to













find rows in the table.  The alternative syntax @code{IGNORE INDEX















(key_list)} can be used to tell MySQL to not use some















particular index.













@findex USE KEY













@findex IGNORE KEY













@code{USE/IGNORE KEY} are synonyms for @code{USE/IGNORE INDEX}.















@end itemize





























Some examples:










@@ -48492,7 +48503,7 @@ with one table and @code{ORDER BY} and with InnoDB tables.













@item















Fixed that @code{SELECT 0 LIMIT 0} doesn't hang thread.















@item













Fixed some problems with @code{USE KEYS} / @code{IGNORE KEYS} when using













Fixed some problems with @code{USE/IGNORE INDEX} when using















many keys with the same start column.















@item















Don't use table scan with BerkeleyDB and InnoDB tables when we can use










@@ -50861,7 +50872,7 @@ Fixed bug in @code{net_clear()} which could give the error @code{Aborted













connection} in the MySQL clients.















@item















Added options @code{USE INDEX (key_list)} and @code{IGNORE INDEX (key_list)} as













join parameters in @code{SELECT}.













parameters in @code{SELECT}.















@item















@code{DELETE} and @code{RENAME} should now work on @code{RAID} tables.















@end itemize