Re: count syntax
От
Tom Lane
Тема
Re: count syntax
Дата
Msg-id
11375.1050071383@sss.pgh.pa.us
Ответ на
count syntax (Patrick Welche)
Список
Дерево обсуждения
count syntax Patrick Welche <prlw1@newn.cam.ac.uk>
Re: count syntax Tom Lane <tgl@sss.pgh.pa.us>
Re: count syntax Bruce Momjian <pgman@candle.pha.pa.us>
Re: count syntax Tom Lane <tgl@sss.pgh.pa.us>
Re: count syntax Bruce Momjian <pgman@candle.pha.pa.us>
Re: count syntax Tom Lane <tgl@sss.pgh.pa.us>
Re: count syntax Bruce Momjian <pgman@candle.pha.pa.us>
psql: FATAL: Missing or erroneous pg_hba.conf file bijoy@openlx.com
Re: psql: FATAL: Missing or erroneous pg_hba.conf file Bruce Momjian <pgman@candle.pha.pa.us>
Re: psql: FATAL: Missing or erroneous pg_hba.conf Ernest E Vogelsinger <ernest@vogelsinger.at>
Re: psql: FATAL: Missing or erroneous pg_hba.conf file Tom Lane <tgl@sss.pgh.pa.us>
Re: count syntax Bruno Wolff III <bruno@wolff.to>
Patrick Welche writes: > What is the difference between the following? > transatlantic=# select count(*) from trans; This is a SQL-spec-mandated special case meaning "count the number of rows". > transatlantic=# select count(trans.flowindex) from trans; This counts the number of non-null values of trans.flowindex. Also per spec. > transatlantic=# select count(trans.*) from trans; ERROR: Memory exhausted in AllocSetAlloc(204) This syntax is not legal per SQL spec. Postgres interprets it as a command to count the number of non-null values of "trans.*", which in this context is taken as being a whole-row variable. Unfortunately the present implementation of whole-row variables leaks memory ... I don't believe that a whole-row variable will ever be null, so the end result is the same as count(*). You may as well spell it in the spec-approved fashion. regards, tom lane
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