Improved USE INDEX / IGNORE INDEX info.

parent 45c02220
......@@ -24779,6 +24779,8 @@ 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
decided to use. The key is @code{NULL} if no index was chosen. If
MySQL chooses the wrong index, you can probably force
......@@ -32810,6 +32812,13 @@ because the column value may not yet be determined when the
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
@example
table_name [[AS] alias] [USE INDEX (key_list)] [IGNORE INDEX (key_list)]
@end example
@item
You can refer to a column as @code{col_name}, @code{tbl_name.col_name}, or
......@@ -33099,6 +33108,8 @@ table_reference NATURAL [RIGHT [OUTER]] JOIN table_reference
@end example
Where @code{table_reference} is defined as:
@findex USE INDEX
@findex IGNORE INDEX
@example
table_name [[AS] alias] [USE INDEX (key_list)] [IGNORE INDEX (key_list)]
@end example
......@@ -33194,6 +33205,8 @@ cases where the join optimiser puts the tables in the wrong order.
@item
@cindex hints
@findex USE INDEX
@findex IGNORE INDEX
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
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