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Postgres FD Implementation
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Abuhujair Javed
Postgres FD Implementation
Commits
97a4dad3
Commit
97a4dad3
authored
Apr 23, 2005
by
Bruce Momjian
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Update H4 tag to H3 to be consistent with heading levels.
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doc/FAQ
View file @
97a4dad3
Frequently Asked Questions (FAQ) for PostgreSQL
Frequently Asked Questions (FAQ) for PostgreSQL
Last updated: Sat Apr 23 14:5
6:4
1 EDT 2005
Last updated: Sat Apr 23 14:5
9:0
1 EDT 2005
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
...
@@ -703,8 +703,7 @@
...
@@ -703,8 +703,7 @@
From psql, type SELECT version();
From psql, type SELECT version();
4.15) Why does my large-object operations get "invalid large obj
4.15) Why does my large-object operations get "invalid large obj descriptor"?
descriptor"?
You need to put BEGIN WORK and COMMIT around any use of a large object
You need to put BEGIN WORK and COMMIT around any use of a large object
handle, that is, surrounding lo_open ... lo_close.
handle, that is, surrounding lo_open ... lo_close.
...
@@ -785,8 +784,8 @@
...
@@ -785,8 +784,8 @@
Extending PostgreSQL
Extending PostgreSQL
5.1) I wrote a user-defined function. When I run it in psql, why does it
5.1) I wrote a user-defined function. When I run it in psql, why does it dump
dump
core?
core?
The problem could be a number of things. Try testing your user-defined
The problem could be a number of things. Try testing your user-defined
function in a stand-alone test program first.
function in a stand-alone test program first.
...
@@ -804,8 +803,7 @@
...
@@ -804,8 +803,7 @@
table-returning function defined in C can be found in
table-returning function defined in C can be found in
contrib/tablefunc.
contrib/tablefunc.
5.4) I have changed a source file. Why does the recompile not see the
5.4) I have changed a source file. Why does the recompile not see the change?
change?
The Makefiles do not have the proper dependencies for include files.
The Makefiles do not have the proper dependencies for include files.
You have to do a make clean and then another make. If you are using
You have to do a make clean and then another make. If you are using
...
...
doc/src/FAQ/FAQ.html
View file @
97a4dad3
...
@@ -10,7 +10,7 @@
...
@@ -10,7 +10,7 @@
alink=
"#0000ff"
>
alink=
"#0000ff"
>
<H1>
Frequently Asked Questions (FAQ) for PostgreSQL
</H1>
<H1>
Frequently Asked Questions (FAQ) for PostgreSQL
</H1>
<P>
Last updated: Sat Apr 23 14:5
6:4
1 EDT 2005
</P>
<P>
Last updated: Sat Apr 23 14:5
9:0
1 EDT 2005
</P>
<P>
Current maintainer: Bruce Momjian (
<A
href=
<P>
Current maintainer: Bruce Momjian (
<A
href=
"mailto:pgman@candle.pha.pa.us"
>
pgman@candle.pha.pa.us
</A>
)
"mailto:pgman@candle.pha.pa.us"
>
pgman@candle.pha.pa.us
</A>
)
...
@@ -133,7 +133,7 @@
...
@@ -133,7 +133,7 @@
<H2
align=
"center"
>
General Questions
</H2>
<H2
align=
"center"
>
General Questions
</H2>
<H
4><A
name=
"1.1"
>
1.1
</A>
) What is PostgreSQL? How is it pronounced?
</H4
>
<H
3><A
name=
"1.1"
>
1.1
</A>
) What is PostgreSQL? How is it pronounced?
</H3
>
<P>
PostgreSQL is pronounced
<I>
Post-Gres-Q-L
</I>
, also called just
<P>
PostgreSQL is pronounced
<I>
Post-Gres-Q-L
</I>
, also called just
<I>
Postgres
</I>
.
</P>
<I>
Postgres
</I>
.
</P>
...
@@ -152,8 +152,8 @@
...
@@ -152,8 +152,8 @@
http://www.postgresql.org/files/documentation/faqs/FAQ_DEV.html
</A>
http://www.postgresql.org/files/documentation/faqs/FAQ_DEV.html
</A>
</P>
</P>
<H
4
><A
name=
"1.2"
>
1.2
</A>
) What is the copyright of
<H
3
><A
name=
"1.2"
>
1.2
</A>
) What is the copyright of
PostgreSQL?
</H
4
>
PostgreSQL?
</H
3
>
<P>
PostgreSQL is distributed under the classic BSD license. It has
<P>
PostgreSQL is distributed under the classic BSD license. It has
no restrictions on how the source code can be used. We like it and
no restrictions on how the source code can be used. We like it and
...
@@ -185,7 +185,7 @@
...
@@ -185,7 +185,7 @@
UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
</P>
SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
</P>
<H
4><A
name=
"1.3"
>
1.3
</A>
) What platforms does PostgreSQL support?
</H4
>
<H
3><A
name=
"1.3"
>
1.3
</A>
) What platforms does PostgreSQL support?
</H3
>
<P>
In general, any modern Unix-compatible platform should be able to
<P>
In general, any modern Unix-compatible platform should be able to
run PostgreSQL. The platforms that had received explicit testing at
run PostgreSQL. The platforms that had received explicit testing at
...
@@ -204,14 +204,14 @@
...
@@ -204,14 +204,14 @@
"http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1&button=Search&key=postgreSQL&stype=all&sort=type&dir=%2F"
>
"http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1&button=Search&key=postgreSQL&stype=all&sort=type&dir=%2F"
>
http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1
&
button=Search
&
key=postgreSQL
&
stype=all
&
sort=type
&
dir=%2F
</a>
.
</p>
http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1
&
button=Search
&
key=postgreSQL
&
stype=all
&
sort=type
&
dir=%2F
</a>
.
</p>
<H
4><A
name=
"1.4"
>
1.4
</A>
) Where can I get PostgreSQL?
</H4
>
<H
3><A
name=
"1.4"
>
1.4
</A>
) Where can I get PostgreSQL?
</H3
>
<P>
Via web browser, use
<a
href=
"http://www.postgresql.org/ftp/"
>
<P>
Via web browser, use
<a
href=
"http://www.postgresql.org/ftp/"
>
http://www.postgresql.org/ftp/
</a>
, and via ftp, use
http://www.postgresql.org/ftp/
</a>
, and via ftp, use
<A
href=
"ftp://ftp.PostgreSQL.org/pub/"
>
<A
href=
"ftp://ftp.PostgreSQL.org/pub/"
>
ftp://ftp.PostgreSQL.org/pub/
</A>
.
</P>
ftp://ftp.PostgreSQL.org/pub/
</A>
.
</P>
<H
4><A
name=
"1.5"
>
1.5
</A>
) Where can I get support?
</H4
>
<H
3><A
name=
"1.5"
>
1.5
</A>
) Where can I get support?
</H3
>
<P>
The PostgreSQL community provides assistance to many of its users
<P>
The PostgreSQL community provides assistance to many of its users
via email. The main web site to subscribe to the email lists is
via email. The main web site to subscribe to the email lists is
...
@@ -230,7 +230,7 @@
...
@@ -230,7 +230,7 @@
"http://techdocs.postgresql.org/companies.php"
>
"http://techdocs.postgresql.org/companies.php"
>
http://techdocs.postgresql.org/companies.php
</A>
.
</P>
http://techdocs.postgresql.org/companies.php
</A>
.
</P>
<H
4><A
name=
"1.6"
>
1.6
</A>
) How do I submit a bug report?
</H4
>
<H
3><A
name=
"1.6"
>
1.6
</A>
) How do I submit a bug report?
</H3
>
<P>
Visit the PostgreSQL bug form at
<A
href=
<P>
Visit the PostgreSQL bug form at
<A
href=
"http://www.postgresql.org/support/submitbug"
>
"http://www.postgresql.org/support/submitbug"
>
...
@@ -240,14 +240,14 @@
...
@@ -240,14 +240,14 @@
"ftp://ftp.PostgreSQL.org/pub/"
>
ftp://ftp.PostgreSQL.org/pub/
</A>
to
"ftp://ftp.PostgreSQL.org/pub/"
>
ftp://ftp.PostgreSQL.org/pub/
</A>
to
see if there is a more recent PostgreSQL version.
</P>
see if there is a more recent PostgreSQL version.
</P>
<H
4><A
name=
"1.7"
>
1.7
</A>
) What is the latest release?
</H4
>
<H
3><A
name=
"1.7"
>
1.7
</A>
) What is the latest release?
</H3
>
<P>
The latest release of PostgreSQL is version 8.0.2.
</P>
<P>
The latest release of PostgreSQL is version 8.0.2.
</P>
<P>
We plan to have a major release every year, with minor releases
<P>
We plan to have a major release every year, with minor releases
every few months.
</P>
every few months.
</P>
<H
4><A
name=
"1.8"
>
1.8
</A>
) What documentation is available?
</H4
>
<H
3><A
name=
"1.8"
>
1.8
</A>
) What documentation is available?
</H3
>
<P>
PostgreSQL includes extensive documentation, including a large
<P>
PostgreSQL includes extensive documentation, including a large
manual, manual pages, and some test examples. See the
<I>
/doc
</I>
manual, manual pages, and some test examples. See the
<I>
/doc
</I>
...
@@ -272,15 +272,15 @@
...
@@ -272,15 +272,15 @@
<P>
Our web site contains even more documentation.
</P>
<P>
Our web site contains even more documentation.
</P>
<H
4
><A
name=
"1.9"
>
1.9
</A>
) How do I find out about known bugs or
<H
3
><A
name=
"1.9"
>
1.9
</A>
) How do I find out about known bugs or
missing features?
</H
4
>
missing features?
</H
3
>
<P>
PostgreSQL supports an extended subset of
<SMALL>
SQL
</SMALL>
-92.
<P>
PostgreSQL supports an extended subset of
<SMALL>
SQL
</SMALL>
-92.
See our
<A
href=
"http://www.postgresql.org/docs/faqs.TODO.html"
>
TODO
</A>
See our
<A
href=
"http://www.postgresql.org/docs/faqs.TODO.html"
>
TODO
</A>
list for known bugs, missing features, and future plans.
</P>
list for known bugs, missing features, and future plans.
</P>
<H
4
><A
name=
"1.10"
>
1.10
</A>
) How can I learn
<H
3
><A
name=
"1.10"
>
1.10
</A>
) How can I learn
<SMALL>
SQL
</SMALL>
?
</H
4
>
<SMALL>
SQL
</SMALL>
?
</H
3
>
<P>
First, consider the PostgreSQL-specific books mentioned above.
<P>
First, consider the PostgreSQL-specific books mentioned above.
Another one is "Teach Yourself SQL in 21 Days, Second Edition"
Another one is "Teach Yourself SQL in 21 Days, Second Edition"
...
@@ -298,14 +298,14 @@
...
@@ -298,14 +298,14 @@
and at
<A
href=
and at
<A
href=
"http://sqlcourse.com/"
>
http://sqlcourse.com.
</A></P>
"http://sqlcourse.com/"
>
http://sqlcourse.com.
</A></P>
<H
4
><A
name=
"1.11"
>
1.11
</A>
) How do I join the development
<H
3
><A
name=
"1.11"
>
1.11
</A>
) How do I join the development
team?
</H
4
>
team?
</H
3
>
<P>
See the
<a
href=
"http://www.postgresql.org/docs/faqs.FAQ_DEV.html"
>
<P>
See the
<a
href=
"http://www.postgresql.org/docs/faqs.FAQ_DEV.html"
>
Developer's FAQ
</A>
.
Developer's FAQ
</A>
.
<H
4
><A
name=
"1.12"
>
1.12
</A>
) How does PostgreSQL compare to other
<H
3
><A
name=
"1.12"
>
1.12
</A>
) How does PostgreSQL compare to other
<SMALL>
DBMS
</SMALL>
s?
</H
4
>
<SMALL>
DBMS
</SMALL>
s?
</H
3
>
<P>
There are several ways of measuring software: features,
<P>
There are several ways of measuring software: features,
performance, reliability, support, and price.
</P>
performance, reliability, support, and price.
</P>
...
@@ -368,8 +368,8 @@
...
@@ -368,8 +368,8 @@
<H2
align=
"center"
>
User Client Questions
</H2>
<H2
align=
"center"
>
User Client Questions
</H2>
<H
4
><A
name=
"2.1"
>
2.1
</A>
) What interfaces are available for
<H
3
><A
name=
"2.1"
>
2.1
</A>
) What interfaces are available for
PostgreSQL?
</H
4
>
PostgreSQL?
</H
3
>
<P>
The PostgreSQL install includes only the
<SMALL>
C
</SMALL>
and embedded
<P>
The PostgreSQL install includes only the
<SMALL>
C
</SMALL>
and embedded
<SMALL>
C
</SMALL>
interfaces. All other interfaces are independent projects
<SMALL>
C
</SMALL>
interfaces. All other interfaces are independent projects
...
@@ -383,8 +383,8 @@
...
@@ -383,8 +383,8 @@
in the
<I>
Drivers/Interfaces
</I>
section and via Internet search.
in the
<I>
Drivers/Interfaces
</I>
section and via Internet search.
</P>
</P>
<H
4
><A
name=
"2.2"
>
2.2
</A>
) What tools are available for using
<H
3
><A
name=
"2.2"
>
2.2
</A>
) What tools are available for using
PostgreSQL with Web pages?
</H
4
>
PostgreSQL with Web pages?
</H
3
>
<P>
A nice introduction to Database-backed Web pages can be seen at:
<P>
A nice introduction to Database-backed Web pages can be seen at:
<A
href=
"http://www.webreview.com"
>
http://www.webreview.com
</A></P>
<A
href=
"http://www.webreview.com"
>
http://www.webreview.com
</A></P>
...
@@ -396,8 +396,8 @@
...
@@ -396,8 +396,8 @@
<P>
For complex cases, many use the Perl and DBD::Pg with CGI.pm or
<P>
For complex cases, many use the Perl and DBD::Pg with CGI.pm or
mod_perl.
</P>
mod_perl.
</P>
<H
4
><A
name=
"2.3"
>
2.3
</A>
) Does PostgreSQL have a graphical user
<H
3
><A
name=
"2.3"
>
2.3
</A>
) Does PostgreSQL have a graphical user
interface?
</H
4
>
interface?
</H
3
>
<P>
Yes, see
<a
href=
"http://techdocs.postgresql.org/guides/GUITools"
>
<P>
Yes, see
<a
href=
"http://techdocs.postgresql.org/guides/GUITools"
>
http://techdocs.postgresql.org/guides/GUITools
</a>
for a
http://techdocs.postgresql.org/guides/GUITools
</a>
for a
...
@@ -408,14 +408,14 @@
...
@@ -408,14 +408,14 @@
<H2
align=
"center"
>
Administrative Questions
</H2>
<H2
align=
"center"
>
Administrative Questions
</H2>
<H
4
><A
name=
"3.1"
>
3.1
</A>
) How do I install PostgreSQL somewhere
<H
3
><A
name=
"3.1"
>
3.1
</A>
) How do I install PostgreSQL somewhere
other than
<I>
/usr/local/pgsql
</I>
?
</H
4
>
other than
<I>
/usr/local/pgsql
</I>
?
</H
3
>
<P>
Specify the
<I>
--prefix
</I>
option when running
<P>
Specify the
<I>
--prefix
</I>
option when running
<I>
configure
</I>
.
</P>
<I>
configure
</I>
.
</P>
<H
4
><A
name=
"3.2"
>
3.2
</A>
) How do I control connections from other
<H
3
><A
name=
"3.2"
>
3.2
</A>
) How do I control connections from other
hosts?
</H
4
>
hosts?
</H
3
>
<P>
By default, PostgreSQL only allows connections from the local
<P>
By default, PostgreSQL only allows connections from the local
machine using Unix domain sockets or TCP/IP connections. Other
machine using Unix domain sockets or TCP/IP connections. Other
...
@@ -424,8 +424,8 @@
...
@@ -424,8 +424,8 @@
host-based authentication by modifying the
host-based authentication by modifying the
<I>
$PGDATA/pg_hba.conf
</I>
file, and restart the server.
</P>
<I>
$PGDATA/pg_hba.conf
</I>
file, and restart the server.
</P>
<H
4
><A
name=
"3.3"
>
3.3
</A>
) How do I tune the database engine for
<H
3
><A
name=
"3.3"
>
3.3
</A>
) How do I tune the database engine for
better performance?
</H
4
>
better performance?
</H
3
>
<P>
There are three major areas for potential performance
<P>
There are three major areas for potential performance
improvement:
</P>
improvement:
</P>
...
@@ -481,15 +481,15 @@
...
@@ -481,15 +481,15 @@
</DD>
</DD>
</DL>
</DL>
<H
4
><A
name=
"3.4"
>
3.4
</A>
) What debugging features are
<H
3
><A
name=
"3.4"
>
3.4
</A>
) What debugging features are
available?
</H
4
>
available?
</H
3
>
<P>
There are many
<CODE>
log_*
</CODE>
server configuration variables
<P>
There are many
<CODE>
log_*
</CODE>
server configuration variables
that enable printing of query and process statistics which can be
that enable printing of query and process statistics which can be
very useful for debugging and performance measurements.
</P>
very useful for debugging and performance measurements.
</P>
<H
4
><A
name=
"3.5"
>
3.5
</A>
) Why do I get
<I>
"Sorry, too many
<H
3
><A
name=
"3.5"
>
3.5
</A>
) Why do I get
<I>
"Sorry, too many
clients"
</I>
when trying to connect?
</H
4
>
clients"
</I>
when trying to connect?
</H
3
>
<P>
You have reached the default limit is 100 database sessions. You
<P>
You have reached the default limit is 100 database sessions. You
need to increase the
<I>
postmaster
</I>
's limit on how many
need to increase the
<I>
postmaster
</I>
's limit on how many
...
@@ -497,8 +497,8 @@
...
@@ -497,8 +497,8 @@
<I>
max_connections
</I>
value in
<I>
postgresql.conf
</I>
and
<I>
max_connections
</I>
value in
<I>
postgresql.conf
</I>
and
restarting the
<I>
postmaster
</I>
.
</P>
restarting the
<I>
postmaster
</I>
.
</P>
<H
4
><A
name=
"3.6"
>
3.6
</A>
) Why do I need to do a dump and restore
<H
3
><A
name=
"3.6"
>
3.6
</A>
) Why do I need to do a dump and restore
to upgrade between major PostgreSQL releases?
</H
4
>
to upgrade between major PostgreSQL releases?
</H
3
>
<P>
The PostgreSQL team makes only small changes between minor releases,
<P>
The PostgreSQL team makes only small changes between minor releases,
so upgrading from 7.4.0 to 7.4.1 does not require a dump and restore.
so upgrading from 7.4.0 to 7.4.1 does not require a dump and restore.
...
@@ -508,7 +508,7 @@
...
@@ -508,7 +508,7 @@
data in a generic format that can then be loaded in using the new internal
data in a generic format that can then be loaded in using the new internal
format.
</P>
format.
</P>
<H
4><A
name=
"3.7"
>
3.7
</A>
) What computer hardware should I use?
</H4
>
<H
3><A
name=
"3.7"
>
3.7
</A>
) What computer hardware should I use?
</H3
>
<P>
Because PC hardware is mostly compatible, people tend to believe that
<P>
Because PC hardware is mostly compatible, people tend to believe that
all PC hardware is of equal quality. It is not. ECC RAM, SCSI, and
all PC hardware is of equal quality. It is not. ECC RAM, SCSI, and
...
@@ -522,8 +522,8 @@
...
@@ -522,8 +522,8 @@
<H2
align=
"center"
>
Operational Questions
</H2>
<H2
align=
"center"
>
Operational Questions
</H2>
<H
4
><A
name=
"4.1"
>
4.1
</A>
) How do I
<SMALL>
SELECT
</SMALL>
only the
<H
3
><A
name=
"4.1"
>
4.1
</A>
) How do I
<SMALL>
SELECT
</SMALL>
only the
first few rows of a query? A random row?
</H
4
>
first few rows of a query? A random row?
</H
3
>
<P>
To retrieve only a few rows, if you know at the number of rows
<P>
To retrieve only a few rows, if you know at the number of rows
needed at the time of the
<SMALL>
SELECT
</SMALL>
use
needed at the time of the
<SMALL>
SELECT
</SMALL>
use
...
@@ -541,9 +541,9 @@
...
@@ -541,9 +541,9 @@
LIMIT 1;
LIMIT 1;
</PRE>
</PRE>
<H
4
><A
name=
"4.2"
>
4.2
</A>
) How do I find out what tables, indexes,
<H
3
><A
name=
"4.2"
>
4.2
</A>
) How do I find out what tables, indexes,
databases, and users are defined? How do I see the queries used
databases, and users are defined? How do I see the queries used
by
<I>
psql
</I>
to display them?
</H
4
>
by
<I>
psql
</I>
to display them?
</H
3
>
<P>
Use the \dt command to see tables in
<I>
psql
</I>
. For a complete list of
<P>
Use the \dt command to see tables in
<I>
psql
</I>
. For a complete list of
commands inside psql you can use \?. Alternatively you can read the source
commands inside psql you can use \?. Alternatively you can read the source
...
@@ -564,7 +564,7 @@
...
@@ -564,7 +564,7 @@
illustrates many of the
<SMALL>
SELECT
</SMALL>
s needed to get
illustrates many of the
<SMALL>
SELECT
</SMALL>
s needed to get
information from the database system tables.
</P>
information from the database system tables.
</P>
<H
4><A
name=
"4.3"
>
4.3
</A>
) How do you change a column's data type?
</H4
>
<H
3><A
name=
"4.3"
>
4.3
</A>
) How do you change a column's data type?
</H3
>
<P>
Changing the data type of a column can be done easily in 8.0
<P>
Changing the data type of a column can be done easily in 8.0
and later with
<SMALL>
ALTER TABLE ALTER COLUMN TYPE
</SMALL>
.
</P>
and later with
<SMALL>
ALTER TABLE ALTER COLUMN TYPE
</SMALL>
.
</P>
...
@@ -580,8 +580,8 @@
...
@@ -580,8 +580,8 @@
<P>
You might then want to do
<I>
VACUUM FULL tab
</I>
to reclaim the
<P>
You might then want to do
<I>
VACUUM FULL tab
</I>
to reclaim the
disk space used by the expired rows.
</P>
disk space used by the expired rows.
</P>
<H
4
><A
name=
"4.4"
>
4.4
</A>
) What is the maximum size for a row, a
<H
3
><A
name=
"4.4"
>
4.4
</A>
) What is the maximum size for a row, a
table, and a database?
</H
4
>
table, and a database?
</H
3
>
<P>
These are the limits:
</P>
<P>
These are the limits:
</P>
<BLOCKQUOTE>
<BLOCKQUOTE>
...
@@ -611,8 +611,8 @@ table?</TD><TD>unlimited</TD></TR>
...
@@ -611,8 +611,8 @@ table?</TD><TD>unlimited</TD></TR>
<P>
The maximum table size and maximum number of columns can be
<P>
The maximum table size and maximum number of columns can be
quadrupled by increasing the default block size to 32k.
</P>
quadrupled by increasing the default block size to 32k.
</P>
<H
4
><A
name=
"4.5"
>
4.5
</A>
) How much database disk space is required
<H
3
><A
name=
"4.5"
>
4.5
</A>
) How much database disk space is required
to store data from a typical text file?
</H
4
>
to store data from a typical text file?
</H
3
>
<P>
A PostgreSQL database may require up to five times the disk
<P>
A PostgreSQL database may require up to five times the disk
space to store data from a text file.
</P>
space to store data from a text file.
</P>
...
@@ -648,8 +648,8 @@ table?</TD><TD>unlimited</TD></TR>
...
@@ -648,8 +648,8 @@ table?</TD><TD>unlimited</TD></TR>
<P><SMALL>
NULL
</SMALL>
s are stored as bitmaps, so they
<P><SMALL>
NULL
</SMALL>
s are stored as bitmaps, so they
use very little space.
</P>
use very little space.
</P>
<H
4
><A
name=
"4.6"
>
4.6
</A>
) Why are my queries slow? Why don't they
<H
3
><A
name=
"4.6"
>
4.6
</A>
) Why are my queries slow? Why don't they
use my indexes?
</H
4
>
use my indexes?
</H
3
>
<P>
Indexes are not used by every query. Indexes are used only if the
<P>
Indexes are not used by every query. Indexes are used only if the
table is larger than a minimum size, and the query selects only a
table is larger than a minimum size, and the query selects only a
...
@@ -712,14 +712,14 @@ table?</TD><TD>unlimited</TD></TR>
...
@@ -712,14 +712,14 @@ table?</TD><TD>unlimited</TD></TR>
types exactly match the index's column types. This was particularly
types exactly match the index's column types. This was particularly
true of int2, int8, and numeric column indexes.
</P>
true of int2, int8, and numeric column indexes.
</P>
<H
4
><A
name=
"4.7"
>
4.7
</A>
) How do I see how the query optimizer is
<H
3
><A
name=
"4.7"
>
4.7
</A>
) How do I see how the query optimizer is
evaluating my query?
</H
4
>
evaluating my query?
</H
3
>
<P>
See the
<SMALL>
EXPLAIN
</SMALL>
manual page.
</P>
<P>
See the
<SMALL>
EXPLAIN
</SMALL>
manual page.
</P>
<H
4
><A
name=
"4.8"
>
4.8
</A>
) How do I perform regular expression
<H
3
><A
name=
"4.8"
>
4.8
</A>
) How do I perform regular expression
searches and case-insensitive regular expression searches? How do I
searches and case-insensitive regular expression searches? How do I
use an index for case-insensitive searches?
</H
4
>
use an index for case-insensitive searches?
</H
3
>
<P>
The
<I>
~
</I>
operator does regular expression matching, and
<P>
The
<I>
~
</I>
operator does regular expression matching, and
<I>
~*
</I>
does case-insensitive regular expression matching. The
<I>
~*
</I>
does case-insensitive regular expression matching. The
...
@@ -740,9 +740,9 @@ table?</TD><TD>unlimited</TD></TR>
...
@@ -740,9 +740,9 @@ table?</TD><TD>unlimited</TD></TR>
CREATE INDEX tabindex ON tab (lower(col));
CREATE INDEX tabindex ON tab (lower(col));
</PRE>
</PRE>
<H
4
><A
name=
"4.9"
>
4.9
</A>
) In a query, how do I detect if a field
<H
3
><A
name=
"4.9"
>
4.9
</A>
) In a query, how do I detect if a field
is
<SMALL>
NULL
</SMALL>
? How can I sort on whether a field is
<SMALL>
is
<SMALL>
NULL
</SMALL>
? How can I sort on whether a field is
<SMALL>
NULL
</SMALL>
or not?
</H
4
>
NULL
</SMALL>
or not?
</H
3
>
<P>
You test the column with
<SMALL>
IS NULL
</SMALL>
and
<SMALL>
IS
<P>
You test the column with
<SMALL>
IS NULL
</SMALL>
and
<SMALL>
IS
NOT NULL
</SMALL>
.
</P>
NOT NULL
</SMALL>
.
</P>
...
@@ -764,8 +764,8 @@ table?</TD><TD>unlimited</TD></TR>
...
@@ -764,8 +764,8 @@ table?</TD><TD>unlimited</TD></TR>
ORDER BY (col IS NOT NULL)
ORDER BY (col IS NOT NULL)
</PRE>
</PRE>
<H
4
><A
name=
"4.10"
>
4.10
</A>
) What is the difference between the
<H
3
><A
name=
"4.10"
>
4.10
</A>
) What is the difference between the
various character types?
</H
4
>
various character types?
</H
3
>
<BLOCKQUOTE>
<BLOCKQUOTE>
<TABLE
>
<TABLE
>
<TR><TH>
Type
</TH><TH>
Internal Name
</TH><TH>
Notes
</TH></TR>
<TR><TH>
Type
</TH><TH>
Internal Name
</TH><TH>
Notes
</TH></TR>
...
@@ -801,8 +801,8 @@ length</TD></TR>
...
@@ -801,8 +801,8 @@ length</TD></TR>
particularly values that include
<SMALL>
NULL
</SMALL>
bytes. All the
particularly values that include
<SMALL>
NULL
</SMALL>
bytes. All the
types described here have similar performance characteristics.
</P>
types described here have similar performance characteristics.
</P>
<H
4
><A
name=
"4.11.1"
>
4.11.1
</A>
) How do I create a
<H
3
><A
name=
"4.11.1"
>
4.11.1
</A>
) How do I create a
serial/auto-incrementing field?
</H
4
>
serial/auto-incrementing field?
</H
3
>
<P>
PostgreSQL supports a
<SMALL>
SERIAL
</SMALL>
data type. It
<P>
PostgreSQL supports a
<SMALL>
SERIAL
</SMALL>
data type. It
auto-creates a sequence. For example,
auto-creates a sequence. For example,
...
@@ -826,8 +826,8 @@ length</TD></TR>
...
@@ -826,8 +826,8 @@ length</TD></TR>
See the
<I>
create_sequence
</I>
manual page for more information
See the
<I>
create_sequence
</I>
manual page for more information
about sequences.
about sequences.
<H
4
><A
name=
"4.11.2"
>
4.11.2
</A>
) How do I get the value of a
<H
3
><A
name=
"4.11.2"
>
4.11.2
</A>
) How do I get the value of a
<SMALL>
SERIAL
</SMALL>
insert?
</H
4
>
<SMALL>
SERIAL
</SMALL>
insert?
</H
3
>
<P>
One approach is to retrieve the next
<SMALL>
SERIAL
</SMALL>
value
<P>
One approach is to retrieve the next
<SMALL>
SERIAL
</SMALL>
value
from the sequence object with the
<I>
nextval()
</I>
function
from the sequence object with the
<I>
nextval()
</I>
function
...
@@ -855,23 +855,23 @@ length</TD></TR>
...
@@ -855,23 +855,23 @@ length</TD></TR>
new_id = execute("SELECT currval('person_id_seq')");
new_id = execute("SELECT currval('person_id_seq')");
</PRE>
</PRE>
<H
4
><A
name=
"4.11.3"
>
4.11.3
</A>
) Doesn't
<I>
currval()
</I>
<H
3
><A
name=
"4.11.3"
>
4.11.3
</A>
) Doesn't
<I>
currval()
</I>
lead to a race condition with other users?
</H
4
>
lead to a race condition with other users?
</H
3
>
<P>
No.
<I>
currval()
</I>
returns the current value assigned by your
<P>
No.
<I>
currval()
</I>
returns the current value assigned by your
session, not by all sessions.
</P>
session, not by all sessions.
</P>
<H
4
><A
name=
"4.11.4"
>
4.11.4
</A>
) Why aren't my sequence numbers
<H
3
><A
name=
"4.11.4"
>
4.11.4
</A>
) Why aren't my sequence numbers
reused on transaction abort? Why are there gaps in the numbering of
reused on transaction abort? Why are there gaps in the numbering of
my sequence/SERIAL column?
</H
4
>
my sequence/SERIAL column?
</H
3
>
<P>
To improve concurrency, sequence values are given out to running
<P>
To improve concurrency, sequence values are given out to running
transactions as needed and are not locked until the transaction
transactions as needed and are not locked until the transaction
completes. This causes gaps in numbering from aborted
completes. This causes gaps in numbering from aborted
transactions.
</P>
transactions.
</P>
<H
4
><A
name=
"4.12"
>
4.12
</A>
) What is an
<SMALL>
OID
</SMALL>
? What is
<H
3
><A
name=
"4.12"
>
4.12
</A>
) What is an
<SMALL>
OID
</SMALL>
? What is
a
<SMALL>
TID
</SMALL>
?
</H
4
>
a
<SMALL>
TID
</SMALL>
?
</H
3
>
<P>
Every row that is created in PostgreSQL gets a unique
<P>
Every row that is created in PostgreSQL gets a unique
<SMALL>
OID
</SMALL>
unless created
<SMALL>
WITHOUT OIDS
</SMALL>
.
<SMALL>
OID
</SMALL>
unless created
<SMALL>
WITHOUT OIDS
</SMALL>
.
...
@@ -893,8 +893,8 @@ length</TD></TR>
...
@@ -893,8 +893,8 @@ length</TD></TR>
are modified or reloaded. They are used by index entries to point
are modified or reloaded. They are used by index entries to point
to physical rows.
</P>
to physical rows.
</P>
<H
4
><A
name=
"4.13"
>
4.13
</A>
) Why do I get the error
<I>
"ERROR:
<H
3
><A
name=
"4.13"
>
4.13
</A>
) Why do I get the error
<I>
"ERROR:
Memory exhausted in AllocSetAlloc()"
</I>
?
</H
4
>
Memory exhausted in AllocSetAlloc()"
</I>
?
</H
3
>
<P>
You probably have run out of virtual memory on your system,
<P>
You probably have run out of virtual memory on your system,
or your kernel has a low limit for certain resources. Try this
or your kernel has a low limit for certain resources. Try this
...
@@ -912,13 +912,13 @@ length</TD></TR>
...
@@ -912,13 +912,13 @@ length</TD></TR>
backend is returning too much data, try it before starting the
backend is returning too much data, try it before starting the
client.
client.
<H
4
><A
name=
"4.14"
>
4.14
</A>
) How do I tell what PostgreSQL version
<H
3
><A
name=
"4.14"
>
4.14
</A>
) How do I tell what PostgreSQL version
I am running?
</H
4
>
I am running?
</H
3
>
<P>
From
<I>
psql
</I>
, type
<CODE>
SELECT version();
</CODE></P>
<P>
From
<I>
psql
</I>
, type
<CODE>
SELECT version();
</CODE></P>
<H
4
><A
name=
"4.15"
>
4.15
</A>
) Why does my large-object operations
<H
3
><A
name=
"4.15"
>
4.15
</A>
) Why does my large-object operations
get
<I>
"invalid large obj descriptor"
</I>
?
</H
4
>
get
<I>
"invalid large obj descriptor"
</I>
?
</H
3
>
<P>
You need to put
<CODE>
BEGIN WORK
</CODE>
and
<CODE>
COMMIT
</CODE>
<P>
You need to put
<CODE>
BEGIN WORK
</CODE>
and
<CODE>
COMMIT
</CODE>
around any use of a large object handle, that is, surrounding
around any use of a large object handle, that is, surrounding
...
@@ -933,15 +933,15 @@ length</TD></TR>
...
@@ -933,15 +933,15 @@ length</TD></TR>
<P>
If you are using a client interface like
<SMALL>
ODBC
</SMALL>
you
<P>
If you are using a client interface like
<SMALL>
ODBC
</SMALL>
you
may need to set
<CODE>
auto-commit off.
</CODE></P>
may need to set
<CODE>
auto-commit off.
</CODE></P>
<H
4
><A
name=
"4.16"
>
4.16
</A>
) How do I create a column that will
<H
3
><A
name=
"4.16"
>
4.16
</A>
) How do I create a column that will
default to the current time?
</H
4
>
default to the current time?
</H
3
>
<P>
Use
<I>
CURRENT_TIMESTAMP
</I>
:
</P>
<P>
Use
<I>
CURRENT_TIMESTAMP
</I>
:
</P>
<PRE>
<PRE>
CREATE TABLE test (x int, modtime TIMESTAMP DEFAULT CURRENT_TIMESTAMP );
CREATE TABLE test (x int, modtime TIMESTAMP DEFAULT CURRENT_TIMESTAMP );
</PRE>
</PRE>
<H
4><A
name=
"4.17"
>
4.17
</A>
) How do I perform an outer join?
</H4
>
<H
3><A
name=
"4.17"
>
4.17
</A>
) How do I perform an outer join?
</H3
>
<P>
PostgreSQL supports outer joins using the SQL standard syntax.
<P>
PostgreSQL supports outer joins using the SQL standard syntax.
Here are two examples:
</P>
Here are two examples:
</P>
...
@@ -964,8 +964,8 @@ length</TD></TR>
...
@@ -964,8 +964,8 @@ length</TD></TR>
<SMALL>
RIGHT
</SMALL>
, and
<SMALL>
FULL
</SMALL>
joins. Ordinary joins
<SMALL>
RIGHT
</SMALL>
, and
<SMALL>
FULL
</SMALL>
joins. Ordinary joins
are called
<SMALL>
INNER
</SMALL>
joins.
</P>
are called
<SMALL>
INNER
</SMALL>
joins.
</P>
<H
4
><A
name=
"4.18"
>
4.18
</A>
) How do I perform queries using
<H
3
><A
name=
"4.18"
>
4.18
</A>
) How do I perform queries using
multiple databases?
</H
4
>
multiple databases?
</H
3
>
<P>
There is no way to query a database other than the current one.
<P>
There is no way to query a database other than the current one.
Because PostgreSQL loads database-specific system catalogs, it is
Because PostgreSQL loads database-specific system catalogs, it is
...
@@ -976,16 +976,16 @@ length</TD></TR>
...
@@ -976,16 +976,16 @@ length</TD></TR>
connections to different databases and merge the results on the
connections to different databases and merge the results on the
client side.
</P>
client side.
</P>
<H
4
><A
name=
"4.19"
>
4.19
</A>
) How do I return multiple rows or
<H
3
><A
name=
"4.19"
>
4.19
</A>
) How do I return multiple rows or
columns from a function?
</H
4
>
columns from a function?
</H
3
>
<P>
It is easy using set-returning functions,
<P>
It is easy using set-returning functions,
<a
href=
"http://techdocs.postgresql.org/guides/SetReturningFunctions"
>
<a
href=
"http://techdocs.postgresql.org/guides/SetReturningFunctions"
>
http://techdocs.postgresql.org/guides/SetReturningFunctions
</a></P>
.
http://techdocs.postgresql.org/guides/SetReturningFunctions
</a></P>
.
<H
4
><A
name=
"4.20"
>
4.20
</A>
) Why do I get "relation with OID #####
<H
3
><A
name=
"4.20"
>
4.20
</A>
) Why do I get "relation with OID #####
does not exist" errors when accessing temporary tables in PL/PgSQL
does not exist" errors when accessing temporary tables in PL/PgSQL
functions?
</H
4
>
functions?
</H
3
>
<P>
PL/PgSQL caches function scripts, and an unfortunate side effect
<P>
PL/PgSQL caches function scripts, and an unfortunate side effect
is that if a PL/PgSQL function accesses a temporary table, and that
is that if a PL/PgSQL function accesses a temporary table, and that
...
@@ -995,8 +995,8 @@ length</TD></TR>
...
@@ -995,8 +995,8 @@ length</TD></TR>
<SMALL>
EXECUTE
</SMALL>
for temporary table access in PL/PgSQL. This
<SMALL>
EXECUTE
</SMALL>
for temporary table access in PL/PgSQL. This
will cause the query to be reparsed every time.
</P>
will cause the query to be reparsed every time.
</P>
<H
4
><A
name=
"4.21"
>
4.21
</A>
) What encryption options are available?
<H
3
><A
name=
"4.21"
>
4.21
</A>
) What encryption options are available?
</H
4
>
</H
3
>
<UL>
<UL>
<LI><I>
contrib/pgcrypto
</I>
contains many encryption functions for
<LI><I>
contrib/pgcrypto
</I>
contains many encryption functions for
use in
<SMALL>
SQL
</SMALL>
queries.
</LI>
use in
<SMALL>
SQL
</SMALL>
queries.
</LI>
...
@@ -1016,21 +1016,21 @@ length</TD></TR>
...
@@ -1016,21 +1016,21 @@ length</TD></TR>
<H2
align=
"center"
>
Extending PostgreSQL
</H2>
<H2
align=
"center"
>
Extending PostgreSQL
</H2>
<H
4
><A
name=
"5.1"
>
5.1
</A>
) I wrote a user-defined function. When I
<H
3
><A
name=
"5.1"
>
5.1
</A>
) I wrote a user-defined function. When I
run it in
<I>
psql
</I>
, why does it dump core?
</H
4
>
run it in
<I>
psql
</I>
, why does it dump core?
</H
3
>
<P>
The problem could be a number of things. Try testing your
<P>
The problem could be a number of things. Try testing your
user-defined function in a stand-alone test program first.
</P>
user-defined function in a stand-alone test program first.
</P>
<H
4
><A
name=
"5.2"
>
5.2
</A>
) How can I contribute some nifty new
<H
3
><A
name=
"5.2"
>
5.2
</A>
) How can I contribute some nifty new
types and functions to PostgreSQL?
</H
4
>
types and functions to PostgreSQL?
</H
3
>
<P>
Send your extensions to the
<I>
pgsql-hackers
</I>
mailing list,
<P>
Send your extensions to the
<I>
pgsql-hackers
</I>
mailing list,
and they will eventually end up in the
<I>
contrib/
</I>
and they will eventually end up in the
<I>
contrib/
</I>
subdirectory.
</P>
subdirectory.
</P>
<H
4
><A
name=
"5.3"
>
5.3
</A>
) How do I write a C function to return a
<H
3
><A
name=
"5.3"
>
5.3
</A>
) How do I write a C function to return a
tuple?
</H
4
>
tuple?
</H
3
>
<P>
In versions of PostgreSQL beginning with 7.3, table-returning
<P>
In versions of PostgreSQL beginning with 7.3, table-returning
functions are fully supported in C, PL/PgSQL, and SQL. See the
functions are fully supported in C, PL/PgSQL, and SQL. See the
...
@@ -1038,8 +1038,8 @@ length</TD></TR>
...
@@ -1038,8 +1038,8 @@ length</TD></TR>
table-returning function defined in C can be found in
table-returning function defined in C can be found in
<I>
contrib/tablefunc
</I>
.
</P>
<I>
contrib/tablefunc
</I>
.
</P>
<H
4
><A
name=
"5.4"
>
5.4
</A>
) I have changed a source file. Why does
<H
3
><A
name=
"5.4"
>
5.4
</A>
) I have changed a source file. Why does
the recompile not see the change?
</H
4
>
the recompile not see the change?
</H
3
>
<P>
The
<I>
Makefiles
</I>
do not have the proper dependencies for
<P>
The
<I>
Makefiles
</I>
do not have the proper dependencies for
include files. You have to do a
<I>
make clean
</I>
and then another
include files. You have to do a
<I>
make clean
</I>
and then another
...
...
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