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Bruce Momjian 2005-04-23 18:57:46 +00:00
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doc/FAQ_DEV
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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)
@ -42,6 +42,7 @@ Technical Questions
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
@ -762,3 +763,37 @@ typedef struct nameData
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.

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doc/src/FAQ/FAQ_DEV.html
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<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>
@ -71,6 +71,8 @@
<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>
@ -941,6 +943,45 @@
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>
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