[HACKERS] calculated fields are not seen in the WHERE clause
Hello, OK select 1 as ccc where 1=1 ERROR select 1 as ccc where ccc=1 PostgreSQL said: ERROR: Attribute 'ccc' not found Is there any way to set conditions on calculated fields values? Best regards, Yar ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
[HACKERS] []performance issues
Hello, Sorry if it's wrong list for the question. Could you suggest some tweaks to the PostgreSQL 7.2.1 to handle the following types of tables faster? Here we have table stats with something over one millon records. Obvious SELECT COUNT(*) FROM stats takes over 40 seconds to execute, and this amount of time does not shorten considerably in subsequent similar requests. All the databases are vacuumed nightly. CREATE TABLE stats ( url varchar(50), src_port varchar(10), ip varchar(16), dst_port varchar(10), proto varchar(10), size int8, login varchar(20), start_date timestamptz, end_date timestamptz, aggregated int4 ); CREATE INDEX aggregated_stats_key ON stats (aggregated); CREATE INDEX ip_stats_key ON stats (ip); stats= explain select count(*) from stats; NOTICE: QUERY PLAN: Aggregate (cost=113331.10..113331.10 rows=1 width=0) - Seq Scan on stats (cost=0.00..110085.28 rows=1298328 width=0) EXPLAIN stats= select count(*) from stats; count - 1298328 (1 row) The system is FreeBSD-4.6-stable, softupdates on, Athlon XP 1500+, 512 Mb DDR, ATA 100 HDD. Thanks in advance, Yar ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [HACKERS] []performance issues
Christopher Kings-Lynne wrote: Doing a row count requires a sequential scan in Postgres. Try creating another summary table that just has one row and one column and is an integer. I have THREE summary tables derived from stats with different levels of aggregation. They work quite fast, But: 1) Summary tables grow too 2) There are requests which cannot be predicted, so they involve the stats table itself. So I am still interested in PostgreSQL's ability to deal with multimillon records tables. Best regards, Yar. ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly