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The big difference between the first two queries is that int the first one, it could go along the index used by the primary key of the table (and used by the ORDER BY clause), then filter out the rows …

You may be interested in the following: http://www.sqlservercentral.com/Forums/Topic558567-149-1.aspx#bm558607 https://stackoverflow.com/questions/1610/can-i-logically-reorder-columns-in-a-table htt …

I have a view which is amazingly slow :) It joins two tables only, having a few simple WHERE conditions and one in a form of a subquery (see SubPlan1 below). The simplest condition is checked as an …

Well, the solution was rephrasing NOT EXISTS to NOT IN. So the index scan and the whole query run quite fast as one would expect.

Besides all the problems normalization solves, this has performance benefits, too. …

The performance of all these will be the very same. If the indexes makes sense or not depends very much on the actual data. (I am pretty sure you don't need all of them, though.) …

A small test: CREATE TABLE test2 ( id serial PRIMARY KEY, num integer, short_text varchar(32), longer_text varchar(1000), long_long_text text ); INSERT INTO test2 (num, short_tex …

No, the query performance will not be affected, or not very much. Indexes are updated on DML statements (and TRUNCATE) while they may or may not be used when executing a query. …

Since the user-post pairing consists exactly these two fields, which can be, expecting extremely high user and post numbers, 2×8 bytes per row, I wouldn't expect performance problems with 10,000 users …

I don't really have the possibility to try jMeter now, so I don't know how following the below advice would affect your tests. Normally benchmarking is done so that after the tests the original datab …

You can create a materialized view on your table: CREATE MATERIALIZED VIEW thecopy AS SELECT * FROM mytable; Then add a unique index that matches your PK on mytable (you cannot add a 'real' PK ther …

I don't know a way to log sequential scans only. Just a small remark: seqscans are not evil, you will get them (especially for smaller tables) all the time. On the other hand, you can definitely log …

Playing a bit with pg_buffercache, I could get answers to some of your questions. This is quite obvious, but the results for (5) also show that answer is YES I am yet to set up a good example for thi …

I would try making two composite partial indexes like CREATE INDEX idx1 ON tw_schedules (scenario_id, type_well_id) WHERE type_well_id IS NOT NULL; CREATE INDEX idx2 ON tw_schedules (scenario_id, tw …

It is quite clear that your 'wrapper' view - while looks like an elegant solution at first - kills the performance involving 7.7M completely unnecessary rows. …