[TYPO3-core] RFC #12897: Cannot parse SQL hints

Xavier Perseguers typo3 at perseguers.ch
Thu Dec 3 13:13:25 CET 2009

Hi David,

> Whats about real SQL-Col-Comments?
> In MySQL it's possible to assign Comments to Cols and in PMA they are 
> visible below the col-titles.
> I used that for an extension but don't know if it's supported in other 
> DBs / DBMSs

We are not speaking here of adding support for comments while creating 
the DB but supporting "comments" (actually hints in my case) within SQL 
queries. Hints allow additional information to be sent to the DBMS while 
performing (typically) a SELECT query.

In case of RealURL, a query is generated like this:

SELECT /*! SQL_NO_CACHE */ content FROM some-realurl-table WHERE ...

The /*! SQL_NO_CACHE */ is a comment but a special comment that is 
understood as a hint by MySQL telling it not to cache the result of the 
query. Dmitry (or Kasper before him?) added this to tweak the 
performance and reliability. However, without this patch, the hint 
cannot be parsed by DBAL.

Xavier Perseguers
DBAL Leader


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