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alink="#0000ff"> |
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<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1> |
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<P>Last updated: Sat Jan 29 22:51:43 EST 2005</P> |
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<P>Last updated: Sat Jan 29 22:59:12 EST 2005</P> |
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<P>Current maintainer: Bruce Momjian (<A href= |
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"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR> |
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@ -56,24 +56,18 @@ |
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<H2 align="center">Administrative Questions</H2> |
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<A href="#3.1">3.1</A>) How do I install PostgreSQL somewhere other |
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than <I>/usr/local/pgsql</I>?<BR> |
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<A href="#3.2">3.2</A>) When I start <I>postmaster</I>, I get a |
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<I>Bad System Call</I> or core dumped message. Why?<BR> |
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<A href="#3.3">3.3</A>) When I try to start <I>postmaster</I>, I |
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get <I>IpcMemoryCreate</I> errors. Why?<BR> |
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<A href="#3.4">3.4</A>) When I try to start <I>postmaster</I>, I |
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get <I>IpcSemaphoreCreate</I> errors. Why?<BR> |
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<A href="#3.5">3.5</A>) How do I control connections from other |
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<A href="#3.2">3.2</A>) How do I control connections from other |
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hosts?<BR> |
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<A href="#3.6">3.6</A>) How do I tune the database engine for |
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<A href="#3.3">3.3</A>) How do I tune the database engine for |
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better performance?<BR> |
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<A href="#3.7">3.7</A>) What debugging features are available?<BR> |
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<A href="#3.8">3.8</A>) Why do I get <I>"Sorry, too many |
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<A href="#3.4">3.4</A>) What debugging features are available?<BR> |
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<A href="#3.5">3.5</A>) Why do I get <I>"Sorry, too many |
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clients"</I> when trying to connect?<BR> |
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<A href="#3.9">3.9</A>) What is in the <I>pgsql_tmp</I> |
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<A href="#3.6">3.6</A>) What is in the <I>pgsql_tmp</I> |
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directory?<BR> |
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<A href="#3.10">3.10</A>) Why do I need to do a dump and restore |
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<A href="#3.7">3.7</A>) Why do I need to do a dump and restore |
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to upgrade PostgreSQL releases?<BR> |
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<A href="#3.11">3.11</A>) What computer hardware should I use?<BR> |
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<A href="#3.8">3.8</A>) What computer hardware should I use?<BR> |
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<H2 align="center">Operational Questions</H2> |
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@ -544,47 +538,7 @@ |
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<P>Specify the <I>--prefix</I> option when running |
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<I>configure</I>.</P> |
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<H4><A name="3.2">3.2</A>) When I start <I>postmaster</I>, I get a |
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<I>Bad System Call</I> or core dumped message. Why?</H4> |
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<P>It could be a variety of problems, but first check to see that |
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you have System V extensions installed in your kernel. PostgreSQL |
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requires kernel support for shared memory and semaphores.</P> |
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<H4><A name="3.3">3.3</A>) When I try to start <I>postmaster</I>, I |
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get <I>IpcMemoryCreate</I> errors. Why?</H4> |
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<P>You either do not have shared memory configured properly in your |
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kernel or you need to enlarge the shared memory available in the |
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kernel. The exact amount you need depends on your architecture and |
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how many buffers and backend processes you configure for |
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<I>postmaster</I>. For most systems, with default numbers of |
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buffers and processes, you need a minimum of ~1 MB. See the <A |
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href="http://www.postgresql.org/docs/current/static/kernel-resources.html">PostgreSQL |
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Administrator's Guide/Server Run-time Environment/Managing Kernel Resources</A> |
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section for more detailed information about shared memory and semaphores.</P> |
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<H4><A name="3.4">3.4</A>) When I try to start <I>postmaster</I>, I |
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get <I>IpcSemaphoreCreate</I> errors. Why?</H4> |
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<P>If the error message is <I>IpcSemaphoreCreate: semget failed (No |
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space left on device)</I> then your kernel is not configured with |
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enough semaphores. Postgres needs one semaphore per potential |
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backend process. A temporary solution is to start <I>postmaster</I> |
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with a smaller limit on the number of backend processes. Use |
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<I>-N</I> with a parameter less than the default of 32. A more |
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permanent solution is to increase your kernel's |
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<SMALL>SEMMNS</SMALL> and <SMALL>SEMMNI</SMALL> parameters.</P> |
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<P>Inoperative semaphores can also cause crashes during heavy |
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database access.</P> |
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<P>If the error message is something else, you might not have |
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semaphore support configured in your kernel at all. See the |
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PostgreSQL Administrator's Guide for more detailed information |
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about shared memory and semaphores.</P> |
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<H4><A name="3.5">3.5</A>) How do I control connections from other |
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<H4><A name="3.2">3.2</A>) How do I control connections from other |
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hosts?</H4> |
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<P>By default, PostgreSQL only allows connections from the local |
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@ -594,7 +548,7 @@ |
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host-based authentication by modifying the file |
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<I>$PGDATA/pg_hba.conf</I> accordingly.</P> |
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<H4><A name="3.6">3.6</A>) How do I tune the database engine for |
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<H4><A name="3.3">3.3</A>) How do I tune the database engine for |
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better performance?</H4> |
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<P>Certainly, indexes can speed up queries. The |
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@ -633,7 +587,7 @@ |
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data in tables to match an index. See the <SMALL>CLUSTER</SMALL> |
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manual page for more details.</P> |
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<H4><A name="3.7">3.7</A>) What debugging features are |
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<H4><A name="3.4">3.4</A>) What debugging features are |
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available?</H4> |
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<P>PostgreSQL has several features that report status information |
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@ -691,7 +645,7 @@ |
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file will be put in the client's current directory. Linux requires |
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a compile with <I>-DLINUX_PROFILE</I> for proper profiling.</P> |
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<H4><A name="3.8">3.8</A>) Why do I get <I>"Sorry, too many |
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<H4><A name="3.5">3.5</A>) Why do I get <I>"Sorry, too many |
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clients"</I> when trying to connect?</H4> |
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<P>You need to increase <I>postmaster</I>'s limit on how many |
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@ -716,7 +670,7 @@ |
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the number of allowed backend processes is so your system won't run |
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out of resources.</P> |
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<H4><A name="3.9">3.9</A>) What is in the <I>pgsql_tmp</I> directory?</H4> |
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<H4><A name="3.6">3.6</A>) What is in the <I>pgsql_tmp</I> directory?</H4> |
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<P>This directory contains temporary files generated by the query |
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executor. For example, if a sort needs to be done to satisfy an |
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@ -728,7 +682,7 @@ |
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remain if a backend crashes during a sort. A stop and restart of the |
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<I>postmaster</I> will remove files from those directories.</P> |
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<H4><A name="3.10">3.10</A>) Why do I need to do a dump and restore |
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<H4><A name="3.7">3.7</A>) Why do I need to do a dump and restore |
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to upgrade between major PostgreSQL releases?</H4> |
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<P>The PostgreSQL team makes only small changes between minor releases, |
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@ -744,7 +698,7 @@ |
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The release notes mention whether <I>pg_upgrade</I> is available for the |
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release.</P> |
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<H4><A name="3.11">3.11</A>) What computer hardware should I use?</H4> |
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<H4><A name="3.8">3.8</A>) What computer hardware should I use?</H4> |
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<P>Because PC hardware is mostly compatible, people tend to believe that |
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all PC hardware is of equal quality. It is not. ECC RAM, SCSI, and |
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Bruce Momjian
21 years ago