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@ -10,7 +10,7 @@ |
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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 Apr 23 11:22:46 EDT 2005</P> |
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<P>Last updated: Sat Apr 23 14:56:41 EDT 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>) |
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@ -192,10 +192,9 @@ |
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the time of release are listed in the installation |
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instructions.</P> |
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<P>Starting with version 8.0, PostgreSQL now runs natively on |
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Microsoft Windows NT-based operating systems like Win2000, WinXP, |
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and Win2003. A prepackaged installer is available at <a href= |
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"http://pgfoundry.org/projects/pginstaller"> |
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<P>PostgreSQL also runs natively on Microsoft Windows NT-based operating |
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systems like Win2000, WinXP, and Win2003. A prepackaged installer is |
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available at <a href= "http://pgfoundry.org/projects/pginstaller"> |
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http://pgfoundry.org/projects/pginstaller</a>. MSDOS-based versions |
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of Windows (Win95, Win98, WinMe) can run PostgreSQL using Cygwin.</P> |
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@ -207,9 +206,10 @@ |
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<H4><A name="1.4">1.4</A>) Where can I get PostgreSQL?</H4> |
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<P>The primary anonymous ftp site for PostgreSQL is <A href= |
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"ftp://ftp.PostgreSQL.org/pub/">ftp://ftp.PostgreSQL.org/pub/</A>. |
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For mirror sites, see our main web site.</P> |
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<P>Via web browser, use <a href="http://www.postgresql.org/ftp/"> |
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http://www.postgresql.org/ftp/</a>, and via ftp, use |
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<A href="ftp://ftp.PostgreSQL.org/pub/"> |
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ftp://ftp.PostgreSQL.org/pub/</A>.</P> |
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<H4><A name="1.5">1.5</A>) Where can I get support?</H4> |
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@ -222,7 +222,7 @@ |
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<P>The major IRC channel is <I>#postgresql</I> on Freenode |
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(<I>irc.freenode.net</I>). To connect you can use the Unix |
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program <CODE>irc -c '#postgresql' "$USER" irc.freenode.net</CODE> |
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or use any of the other popular IRC clients. A Spanish one also exists |
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or use any other IRC clients. A Spanish one also exists |
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on the same network, (<I>#postgresql-es</I>), and a French one, |
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(<I>#postgresqlfr</I>). There is also a PostgreSQL channel on EFNet.</P> |
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@ -244,7 +244,8 @@ |
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<P>The latest release of PostgreSQL is version 8.0.2.</P> |
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<P>We plan to have major releases every ten to twelve months.</P> |
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<P>We plan to have a major release every year, with minor releases |
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every few months.</P> |
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<H4><A name="1.8">1.8</A>) What documentation is available?</H4> |
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@ -275,18 +276,21 @@ |
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missing features?</H4> |
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<P>PostgreSQL supports an extended subset of <SMALL>SQL</SMALL>-92. |
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See our <A href="http://developer.PostgreSQL.org/todo.php">TODO</A> |
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See our <A href="http://www.postgresql.org/docs/faqs.TODO.html">TODO</A> |
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list for known bugs, missing features, and future plans.</P> |
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<H4><A name="1.10">1.10</A>) How can I learn |
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<SMALL>SQL</SMALL>?</H4> |
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<P>The PostgreSQL book at <A href= |
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"http://www.postgresql.org/docs/books/awbook.html">http://www.postgresql.org/docs/books/awbook.html</A> |
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teaches <SMALL>SQL</SMALL>. There is another PostgreSQL book at <A |
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href= |
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"http://www.commandprompt.com/ppbook/">http://www.commandprompt.com/ppbook.</A> |
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There is a nice tutorial at <A href= |
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<P>First, consider the PostgreSQL-specific books mentioned above. |
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Another one is "Teach Yourself SQL in 21 Days, Second Edition" |
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at <A href= |
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"http://members.tripod.com/er4ebus/sql/index.htm">http://members.tripod.com/er4ebus/sql/index.htm</A></P> |
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Many of our users like <I>The Practical SQL Handbook</I>, |
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Bowman, Judith S., et al., Addison-Wesley. Others like <I>The |
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Complete Reference SQL</I>, Groff et al., McGraw-Hill.</P> |
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There is also a nice tutorial at <A href= |
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"http://www.intermedia.net/support/sql/sqltut.shtm">http://www.intermedia.net/support/sql/sqltut.shtm,</A> |
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at <A href= |
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"http://ourworld.compuserve.com/homepages/graeme_birchall/HTM_COOK.HTM"> |
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@ -294,28 +298,11 @@ |
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and at <A href= |
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"http://sqlcourse.com/">http://sqlcourse.com.</A></P> |
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<P>Another one is "Teach Yourself SQL in 21 Days, Second Edition" |
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at <A href= |
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"http://members.tripod.com/er4ebus/sql/index.htm">http://members.tripod.com/er4ebus/sql/index.htm</A></P> |
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<P>Many of our users like <I>The Practical SQL Handbook</I>, |
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Bowman, Judith S., et al., Addison-Wesley. Others like <I>The |
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Complete Reference SQL</I>, Groff et al., McGraw-Hill.</P> |
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<H4><A name="1.11">1.11</A>) How do I join the development |
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team?</H4> |
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<P>First, download the latest source and read the PostgreSQL |
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Developers FAQ and documentation on our web site, or in the |
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distribution. Second, subscribe to the <I>pgsql-hackers</I> and |
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<I>pgsql-patches</I> mailing lists. Third, submit high quality |
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patches to pgsql-patches.</P> |
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<P>There are about a dozen people who have commit privileges to the |
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PostgreSQL <SMALL>CVS</SMALL> archive. They each have submitted so |
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many high-quality patches that it was impossible for the existing |
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committers to keep up, and we had confidence that patches they |
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committed were of high quality.</P> |
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<P>See the <a href="http://www.postgresql.org/docs/faqs.FAQ_DEV.html"> |
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Developer's FAQ</A>. |
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<H4><A name="1.12">1.12</A>) How does PostgreSQL compare to other |
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<SMALL>DBMS</SMALL>s?</H4> |
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@ -339,14 +326,7 @@ |
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<DD>PostgreSQL's performance is comparable to other commercial and |
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open source databases. It is faster for some things, slower for |
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others. In comparison to MySQL or leaner database systems, we are |
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faster for multiple users, complex queries, and a read/write query |
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load. MySQL is faster for simple SELECT queries done by a few users. |
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Of course, MySQL does not have most of the features mentioned in the |
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<I>Features</I> section above. We are built for reliability and |
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features, and we continue to improve performance in every |
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release. <BR> |
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<BR> |
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others. Our performance is usually +/-10% compared to other databases. |
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</DD> |
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<DT><B>Reliability</B></DT> |
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@ -419,22 +399,8 @@ |
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<H4><A name="2.3">2.3</A>) Does PostgreSQL have a graphical user |
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interface?</H4> |
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<P>Yes, there are several graphical interfaces to PostgreSQL |
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available. These include pgAdmin III (<a |
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href="http://www.pgadmin.org">http://www.pgadmin.org</a>, PgAccess |
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<a href="http://www.pgaccess.org"> http://www.pgaccess.org</a>), |
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RHDB Admin (<a |
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href="http://sources.redhat.com/rhdb/">http://sources.redhat.com/rhdb/ |
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</a>), TORA (<a href="http://www.globecom.net/tora/"> |
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http://www.globecom.net/tora/</a>, partly commercial), and Rekall (<a |
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href="http://www.rekallrevealed.org/"> |
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http://www.rekallrevealed.org/</a>). There is also PhpPgAdmin (<a |
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href="http://phppgadmin.sourceforge.net/"> |
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http://phppgadmin.sourceforge.net/ </a>), a web-based interface to |
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PostgreSQL.</P> |
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<P>See <a href="http://techdocs.postgresql.org/guides/GUITools"> |
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http://techdocs.postgresql.org/guides/GUITools</a> for a more |
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<P>Yes, see <a href="http://techdocs.postgresql.org/guides/GUITools"> |
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http://techdocs.postgresql.org/guides/GUITools</a> for a |
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detailed list.</P> |
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<HR> |
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@ -522,48 +488,6 @@ |
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that enable printing of query and process statistics which can be |
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very useful for debugging and performance measurements.</P> |
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<P><B>The following detailed debug instructions are to be used to |
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provide more detailed information for server developers debugging a |
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problem.</B></P> |
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<P>It is also possible to debug the server if it isn't operating |
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properly. First, by running <I>configure</I> with the --enable-cassert |
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option, many <I>assert()</I>s monitor the progress of the backend |
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and halt the program when something unexpected occurs.</P> |
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<P>The <I>postmaster</I> has a <I>-d</I> option that allows even more |
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detailed information to be reported. The <I>-d</I> option takes a |
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number that specifies the debug level. Be warned that high debug |
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level values generate large log files.</P> |
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<P>If <I>postmaster</I> is not running, you can actually run the |
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<I>postgres</I> backend from the command line, and type your |
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<SMALL>SQL</SMALL> statement directly. This is recommended |
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<B>only</B> for debugging purposes. Note that a newline terminates |
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the query, not a semicolon. If you have compiled with debugging |
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symbols, you can use a debugger to see what is happening. Because |
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the backend was not started from <I>postmaster</I>, it is not |
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running in an identical environment and locking/backend interaction |
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problems may not be duplicated.</P> |
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<P>If <I>postmaster</I> is running, start <I>psql</I> in one |
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window, then find the <SMALL>PID</SMALL> of the <I>postgres</I> |
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process used by <I>psql</I> using <CODE>SELECT pg_backend_pid()</CODE>. |
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Use a debugger to attach to the <I>postgres</I> <SMALL>PID</SMALL>. |
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You can set breakpoints in the debugger and issue queries from |
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<I>psql</I>. If you are debugging <I>postgres</I> startup, you can |
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set PGOPTIONS="-W n", then start <I>psql</I>. This will cause startup |
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to delay for <I>n</I> seconds so you can attach to the process with |
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the debugger, set any breakpoints, and continue through the startup |
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sequence.</P> |
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<P>You can also compile with profiling to see what functions are |
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taking execution time. The backend profile files will be deposited |
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in the <I>pgsql/data/base/dbname</I> directory. The client profile |
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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="3.5">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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@ -577,7 +501,7 @@ |
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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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so upgrading from 7.4 to 7.4.1 does not require a dump and restore. |
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so upgrading from 7.4.0 to 7.4.1 does not require a dump and restore. |
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However, major releases (e.g. from 7.3 to 7.4) often change the internal |
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format of system tables and data files. These changes are often complex, |
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so we don't maintain backward compatibility for data files. A dump outputs |
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@ -727,11 +651,11 @@ table?</TD><TD>unlimited</TD></TR> |
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<H4><A name="4.6">4.6</A>) Why are my queries slow? Why don't they |
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use my indexes?</H4> |
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<P>Indexes are not automatically used by every query. Indexes are only |
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used if the table is larger than a minimum size, and the query |
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selects only a small percentage of the rows in the table. This is |
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because the random disk access caused by an index scan can be |
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slower than a straight read through the table, or sequential scan. </P> |
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<P>Indexes are not used by every query. Indexes are used only if the |
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table is larger than a minimum size, and the query selects only a |
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small percentage of the rows in the table. This is because the random |
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disk access caused by an index scan can be slower than a straight read |
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through the table, or sequential scan. </P> |
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<P>To determine if an index should be used, PostgreSQL must have |
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statistics about the table. These statistics are collected using |
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Bruce Momjian
21 years ago