MySQL Bugs: #29997: Possible typo in 'IS NULL optimization' docs

Bug #29997	Possible typo in 'IS NULL optimization' docs
Submitted:	24 Jul 2007 3:27	Modified:	24 Jul 2007 15:26
Reporter:	Baron Schwartz (Basic Quality Contributor)	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	All	OS:	Any
Assigned to:	Paul DuBois	CPU Architecture:	Any

Description:
From http://dev.mysql.com/doc/refman/5.0/en/is-null-optimization.html,

"MySQL can also optimize the combination col_name = expr AND col_name IS NULL, a form that is common in resolved subqueries. EXPLAIN shows ref_or_null  when this optimization is used."

But from http://dev.mysql.com/doc/refman/5.0/en/explain.html,

"ref_or_null

This join type is like ref, but with the addition that MySQL does an extra search for rows that contain NULL values. This join type optimization is used most often in resolving subqueries. In the following examples, MySQL can use a ref_or_null join to process ref_table:

SELECT * FROM ref_table
  WHERE key_column=expr OR key_column IS NULL;"

The difference is the first example says AND instead of OR.  "col_name = expr AND col_name IS NULL" is always false.  I think it's a typo and should be "col_name = expr OR col_name IS NULL."

How to repeat:
Doc bug.

Thank you for the report.

Verified as described.

Thank you for your bug report. This issue has been addressed in the documentation. The updated documentation will appear on our website shortly, and will be included in the next release of the relevant products.