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Updates from Ian Barwick.

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Bruce Momjian
2002-10-21 00:47:44 +00:00
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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
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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
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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.
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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