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author | Bruce Momjian <bruce@momjian.us> | 2002-10-21 00:47:44 +0000 |
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committer | Bruce Momjian <bruce@momjian.us> | 2002-10-21 00:47:44 +0000 |
commit | 189c3481c447bed619c96b7801f06f75fadf8fdd (patch) | |
tree | f6c2d755f61b594beabd1380c1f5fd6f6fe62d0d /doc/FAQ | |
parent | 24af7929ceb2abc6e531d7053d99f8b66e4d44d6 (diff) | |
download | postgresql-189c3481c447bed619c96b7801f06f75fadf8fdd.tar.gz postgresql-189c3481c447bed619c96b7801f06f75fadf8fdd.zip |
Updates from Ian Barwick.
Diffstat (limited to 'doc/FAQ')
-rw-r--r-- | doc/FAQ | 41 |
1 files changed, 19 insertions, 22 deletions
@@ -1,7 +1,7 @@ Frequently Asked Questions (FAQ) for PostgreSQL - Last updated: Sat Oct 19 22:58:02 EDT 2002 + Last updated: Sun Oct 20 20:47:14 EDT 2002 Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) @@ -339,7 +339,7 @@ the Features section above. We are built for reliability and features, though we continue to improve performance in every release. There is an interesting Web page comparing PostgreSQL - to MySQL at http://openacs.org/why-not-mysql.html + to MySQL at http://openacs.org/philosophy/why-not-mysql.html Reliability We realize that a DBMS must be reliable, or it is worthless. We @@ -596,12 +596,12 @@ was 64, and changing it required a rebuild after altering the MaxBackendId constant in include/storage/sinvaladt.h. - 3.9) What are the pgsql_tmp directory? + 3.9) What is in the pgsql_tmp directory? - They are temporary files generated by the query executor. For example, - if a sort needs to be done to satisfy an ORDER BY, and the sort - requires more space than the backend's -S parameter allows, then - temporary files are created to hold the extra data. + This directory contains temporary files generated by the query + executor. For example, if a sort needs to be done to satisfy an ORDER + BY and the sort requires more space than the backend's -S parameter + allows, then temporary files are created here to hold the extra data. The temporary files are usually deleted automatically, but might remain if a backend crashes during a sort. A stop and restart of the @@ -758,19 +758,16 @@ When using wild-card operators such as LIKE or ~, indexes can only be used in certain circumstances: * The beginning of the search string must be anchored to the start - of the string, i.e.: + of the string, i.e. + + LIKE patterns must not start with %. + + ~ (regular expression) patterns must start with ^. + * The search string can not start with a character class, e.g. + [a-e]. + * Case-insensitive searches such as ILIKE and ~* do not utilise + indexes. Instead, use functional indexes, which are described in + section 4.12. + * The default C locale must be used during initdb. - * LIKE patterns must not start with %. - * ~ (regular expression) patterns must start with ^. - - The search string can not start with a character class, e.g. [a-e]. - - Case-insensitive searches such as ILIKE and ~* do not utilise - indexes. Instead, use functional indexes, which are described in - section 4.12. - - The default C locale must be used during initdb. - 4.9) How do I see how the query optimizer is evaluating my query? See the EXPLAIN manual page. @@ -1057,7 +1054,7 @@ CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP ); Because PostgreSQL loads database-specific system catalogs, it is uncertain how a cross-database query should even behave. - /contrib/dblink allows cross-database queries using function calls. Of + contrib/dblink allows cross-database queries using function calls. Of course, a client can make simultaneous connections to different databases and merge the results on the client side. @@ -1089,8 +1086,8 @@ CREATE TABLE test (x int, modtime timestamp DEFAULT CURRENT_TIMESTAMP ); 4.28) What encryption options are available? - * /contrib/pgcrypto contains many encryption functions for use in - SQL queries. + * contrib/pgcrypto contains many encryption functions for use in SQL + queries. * The only way to encrypt transmission from the client to the server is by using hostssl in pg_hba.conf. * Database user passwords are automatically encrypted when stored in |