Developer's Frequently Asked Questions (FAQ) for PostgreSQL
- Last updated: Sun Mar 13 22:07:18 EST 2005
+ Last updated: Sat Apr 23 14:57:40 EDT 2005
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
2.5) Why do we use palloc() and pfree() to allocate memory?
2.6) What is ereport()?
2.7) What is CommandCounterIncrement()?
+ 2.8) What debugging features are available?
_________________________________________________________________
General Questions
to be broken into pieces so each piece can see rows modified by
previous pieces. CommandCounterIncrement() increments the Command
Counter, creating a new part of the transaction.
+
+ 2.8) What debugging features are available?
+
+ First, try running configure with the --enable-cassert option, many
+ assert()s monitor the progress of the backend and halt the program
+ when something unexpected occurs.
+
+ The postmaster has a -d option that allows even more detailed
+ information to be reported. The -d option takes a number that
+ specifies the debug level. Be warned that high debug level values
+ generate large log files.
+
+ If the postmaster is not running, you can actually run the postgres
+ backend from the command line, and type your SQL statement directly.
+ This is recommended only for debugging purposes. If you have compiled
+ with debugging symbols, you can use a debugger to see what is
+ happening. Because the backend was not started from postmaster, it is
+ not running in an identical environment and locking/backend
+ interaction problems may not be duplicated.
+
+ If the postmaster is running, start psql in one window, then find the
+ PID of the postgres process used by psql using SELECT
+ pg_backend_pid(). Use a debugger to attach to the postgres PID. You
+ can set breakpoints in the debugger and issue queries from psql. If
+ you are debugging postgres startup, you can set PGOPTIONS="-W n", then
+ start psql. This will cause startup to delay for n seconds so you can
+ attach to the process with the debugger, set any breakpoints, and
+ continue through the startup sequence.
+
+ You can also compile with profiling to see what functions are taking
+ execution time. The backend profile files will be deposited in the
+ pgsql/data/base/dbname directory. The client profile file will be put
+ in the client's current directory. Linux requires a compile with
+ -DLINUX_PROFILE for proper profiling.
<H1>Developer's Frequently Asked Questions (FAQ) for
PostgreSQL</H1>
- <P>Last updated: Sun Mar 13 22:07:18 EST 2005</P>
+ <P>Last updated: Sat Apr 23 14:57:40 EDT 2005</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR>
<I>pfree</I>() to allocate memory?<BR>
<A href="#2.6">2.6</A>) What is ereport()?<BR>
<A href="#2.7">2.7</A>) What is CommandCounterIncrement()?<BR>
+ <A href="#2.8">2.8</A>) What debugging features are available?<BR>
+
<BR>
<HR>
modified by previous pieces. <I>CommandCounterIncrement()</I>
increments the Command Counter, creating a new part of the
transaction.</P>
+
+ <H3><A name="2.8">2.8</A>) What debugging features are
+ available?</H3>
+
+ <P>First, try running <I>configure</I> with the --enable-cassert
+ option, many <I>assert()</I>s monitor the progress of the backend
+ and halt the program when something unexpected occurs.</P>
+
+ <P>The <I>postmaster</I> has a <I>-d</I> option that allows even more
+ detailed information to be reported. The <I>-d</I> option takes a
+ number that specifies the debug level. Be warned that high debug
+ level values generate large log files.</P>
+
+ <P>If the <I>postmaster</I> is not running, you can actually run the
+ <I>postgres</I> backend from the command line, and type your
+ <SMALL>SQL</SMALL> statement directly. This is recommended
+ <B>only</B> for debugging purposes. If you have compiled with debugging
+ symbols, you can use a debugger to see what is happening. Because
+ the backend was not started from <I>postmaster</I>, it is not
+ running in an identical environment and locking/backend interaction
+ problems may not be duplicated.</P>
+
+ <P>If the <I>postmaster</I> is running, start <I>psql</I> in one
+ window, then find the <SMALL>PID</SMALL> of the <I>postgres</I>
+ process used by <I>psql</I> using <CODE>SELECT pg_backend_pid()</CODE>.
+ Use a debugger to attach to the <I>postgres</I> <SMALL>PID</SMALL>.
+ You can set breakpoints in the debugger and issue queries from
+
+ <I>psql</I>. If you are debugging <I>postgres</I> startup, you can
+ set PGOPTIONS="-W n", then start <I>psql</I>. This will cause startup
+ to delay for <I>n</I> seconds so you can attach to the process with
+ the debugger, set any breakpoints, and continue through the startup
+ sequence.</P>
+
+ <P>You can also compile with profiling to see what functions are
+ taking execution time. The backend profile files will be deposited
+ in the <I>pgsql/data/base/dbname</I> directory. The client profile
+ file will be put in the client's current directory. Linux requires
+ a compile with <I>-DLINUX_PROFILE</I> for proper profiling.</P>
</BODY>
</HTML>