On Feb 11, 2008 12:08 PM, Thomas Zaksek <zaksek@xxxxxxxxxxxxxx> wrote: > I have serious performance problems with the following type of queries: > / > /explain analyse SELECT '12.11.2007 18:04:00 UTC' AS zeit, > 'M' AS datatyp, > p.zs_nr AS zs_de, > j_ges, > de_mw_abh_j_lkw(mw_abh) AS j_lkw, > de_mw_abh_v_pkw(mw_abh) AS v_pkw, > de_mw_abh_v_lkw(mw_abh) AS v_lkw, > de_mw_abh_p_bel(mw_abh) AS p_bel > FROM messpunkt p, messungen_v_dat_2007_11_12 m, de_mw w > WHERE m.ganglinientyp = 'M' > AND 381 = m.minute_tag > AND (p.nr, p.mw_nr) = (m.messpunkt, w.nr); > > Explain analze returns > > Nested Loop (cost=0.00..50389.39 rows=3009 width=10) (actual > time=0.503..320.872 rows=2189 loops=1) > -> Nested Loop (cost=0.00..30668.61 rows=3009 width=8) (actual > time=0.254..94.116 rows=2189 loops=1) This nested loop is using us most of your time. Try increasing work_mem and see if it chooses a better join plan, and / or turn off nested loops for a moment and see if that helps. set enable_nestloop = off Note that set enable_xxx = off Is kind of a hammer to the forebrain setting. It's not subtle, and the planner can't work around it. So use them with caution. That said, I had one reporting query that simply wouldn't run fast without turning off nested loops for that one. But don't turn off nested queries universally, they are still a good choice for smaller amounts of data. ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
