Thank you very much Dimitry
2014-08-30 10:41 GMT+02:00 Dmitry Yemanov dim...@users.sourceforge.net [firebird-support] <firebird-support@yahoogroups.com>: > > > 30.08.2014 11:25, Jaume Llunell Gómez wrote: > > > Hi, i would like to understand this plan > > > > PLAN (TABLE1 ORDER TABLE1_IDX1 INDEX (TABLE1_UK)) > > > > And the select that generets it is this one: > > > > SELECT first 1 PREU_COST > > FROM TABLE1 > > WHERE ARTICLE = :p_article > > AND DATA <= :P_DATA > > AND DIVISA = :P_DIVISA > > AND PREU_COST >0 > > ORDER BY DATA DESC,ID DESC > > > > So my question is, does this plan first goes to TABLE1_IDX1 to resolve > > the order by or first uses TABLE1_UK to resolve the where? > > First, index scan for TABLE1_UK is performed to create a bitmap of > records matching the WHERE clause. > > Then, index TABLE1_IDX1 is traversed sequentially in the index order > (aka full index scan) and every record ID found there is checked against > the bitmap. If match is found, then record is returned. > > Dmitry > > >
