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Bruce Momjian 25 years ago
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  1. 116
      doc/FAQ
  2. 112
      doc/src/FAQ/FAQ.html

116
doc/FAQ
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@ -39,24 +39,22 @@
Administrative Questions
3.1) Why does initdb fail?
3.2) How do I install PostgreSQL somewhere other than
3.1) How do I install PostgreSQL somewhere other than
/usr/local/pgsql?
3.3) When I start the postmaster, I get a Bad System Call or core
3.2) When I start the postmaster, I get a Bad System Call or core
dumped message. Why?
3.4) When I try to start the postmaster, I get IpcMemoryCreate errors.
3.3) When I try to start the postmaster, I get IpcMemoryCreate errors.
Why?
3.5) When I try to start the postmaster, I get IpcSemaphoreCreate
3.4) When I try to start the postmaster, I get IpcSemaphoreCreate
errors. Why?
3.6) How do I prevent other hosts from accessing my PostgreSQL
3.5) How do I prevent other hosts from accessing my PostgreSQL
database?
3.7) Why can't I connect to my database from another machine?
3.8) Why can't I access the database as the root user?
3.9) All my servers crash under concurrent table access. Why?
3.10) How do I tune the database engine for better performance?
3.11) What debugging features are available?
3.12) I get "Sorry, too many clients" when trying to connect. Why?
3.13) What are the pg_sorttempNNN.NN files in my database directory?
3.6) Why can't I connect to my database from another machine?
3.7) All my servers crash under concurrent table access. Why?
3.8) How do I tune the database engine for better performance?
3.9) What debugging features are available?
3.10) I get "Sorry, too many clients" when trying to connect. Why?
3.11) What are the pg_sorttempNNN.NN files in my database directory?
Operational Questions
@ -177,15 +175,16 @@
It is possible to compile the libpq C library, psql, and other
interfaces and binaries to run on MS Windows platforms. In this case,
the client is running on MS Windows, and communicates via TCP/IP to a
server running on one of our supported Unix platforms.
server running on one of our supported Unix platforms. A file
win31.mak is included in the distribution for making a Win32 libpq
library and psql.
A file win31.mak is included in the distribution for making a Win32
libpq library and psql.
The database server is now working on Windows NT using Cygwin, the
Cygnus Unix/NT porting library. See pgsql/doc/FAQ_NT in the
distribution. It does not work on MS Windows 9X because Cygwin does
not support the features we need on those platforms.
The database server can run on Windows NT and later using Cygwin, the
Cygnus Unix/NT porting library. See pgsql/doc/FAQ_MSWIN in the
distribution. The database server does not run on MS Windows 9X
because Cygwin does not support the required features on those
platforms. We have no plans to do a native port to any Microsoft
platform.
1.5) Where can I get PostgreSQL?
@ -238,7 +237,7 @@
1.7) What is the latest release?
The latest release of PostgreSQL is version 7.0.2.
The latest release of PostgreSQL is version 7.0.3.
We plan to have major releases every four months.
@ -425,32 +424,18 @@
Administrative Questions
3.1) Why does initdb fail?
Try these:
* check that you don't have any of the previous version's binaries
in your path
* check to see that you have the proper paths set
* check that the postgres user owns the proper files
If you see an error message about oidvector, you definately have a
version mismatch.
3.2) How do I install PostgreSQL somewhere other than /usr/local/pgsql?
3.1) How do I install PostgreSQL somewhere other than /usr/local/pgsql?
The simplest way is to specify the --prefix option when running
configure. If you forgot to do that, you can edit Makefile.global and
change POSTGRESDIR accordingly, or create a Makefile.custom and define
POSTGRESDIR there.
Specify the --prefix option when running configure.
3.3) When I start the postmaster, I get a Bad System Call or core dumped
3.2) When I start the postmaster, I get a Bad System Call or core dumped
message. Why?
It could be a variety of problems, but first check to see that you
have System V extensions installed in your kernel. PostgreSQL requires
kernel support for shared memory and semaphores.
3.4) When I try to start the postmaster, I get IpcMemoryCreate errors. Why?
3.3) When I try to start the postmaster, I get IpcMemoryCreate errors. Why?
You either do not have shared memory configured properly in your
kernel or you need to enlarge the shared memory available in the
@ -459,7 +444,7 @@
For most systems, with default numbers of buffers and processes, you
need a minimum of ~1MB.
3.5) When I try to start the postmaster, I get IpcSemaphoreCreate errors.
3.4) When I try to start the postmaster, I get IpcSemaphoreCreate errors.
Why?
If the error message is IpcSemaphoreCreate: semget failed (No space
@ -473,7 +458,7 @@
If the error message is something else, you might not have semaphore
support configured in your kernel at all.
3.6) How do I prevent other hosts from accessing my PostgreSQL database?
3.5) How do I prevent other hosts from accessing my PostgreSQL database?
By default, PostgreSQL only allows connections from the local machine
using Unix domain sockets. Other machines will not be able to connect
@ -481,26 +466,19 @@
authentication by modifying the file $PGDATA/pg_hba.conf accordingly.
This will allow TCP/IP connections.
3.7) Why can't I connect to my database from another machine?
3.6) Why can't I connect to my database from another machine?
The default configuration allows only unix domain socket connections
from the local machine. To enable TCP/IP connections, make sure the
postmaster has been started with the -i option, and add an appropriate
host entry to the file pgsql/data/pg_hba.conf.
3.8) Why can't I access the database as the root user?
You should not create database users with user id 0 (root). They will
be unable to access the database. This is a security precaution
because of the ability of users to dynamically link object modules
into the database engine.
3.9) All my servers crash under concurrent table access. Why?
3.7) All my servers crash under concurrent table access. Why?
This problem can be caused by a kernel that is not configured to
support semaphores.
3.10) How do I tune the database engine for better performance?
3.8) How do I tune the database engine for better performance?
Certainly, indices can speed up queries. The EXPLAIN command allows
you to see how PostgreSQL is interpreting your query, and which
@ -531,7 +509,7 @@
You can also use the CLUSTER command to group data in tables to match
an index. See the CLUSTER manual page for more details.
3.11) What debugging features are available?
3.9) What debugging features are available?
PostgreSQL has several features that report status information that
can be valuable for debugging purposes.
@ -578,7 +556,7 @@
pgsql/data/base/dbname directory. The client profile file will be put
in the client's current directory.
3.12) I get 'Sorry, too many clients' when trying to connect. Why?
3.10) I get 'Sorry, too many clients' when trying to connect. Why?
You need to increase the postmaster's limit on how many concurrent
backend processes it can start.
@ -606,7 +584,7 @@
was 64, and changing it required a rebuild after altering the
MaxBackendId constant in include/storage/sinvaladt.h.
3.13) What are the pg_sorttempNNN.NN files in my database directory?
3.11) What are the pg_sorttempNNN.NN files in my database directory?
They are temporary files generated by the query executor. For example,
if a sort needs to be done to satisfy an ORDER BY, and the sort
@ -645,9 +623,9 @@
4.4) How do I get a list of tables or other things I can see in psql?
You can read the source code for psql in file
pgsql/src/bin/psql/psql.c. It contains SQL commands that generate the
output for psql's backslash commands. You can also start psql with the
-E option so it will print out the queries it uses to execute the
pgsql/src/bin/psql/describe.c. It contains SQL commands that generate
the output for psql's backslash commands. You can also start psql with
the -E option so it will print out the queries it uses to execute the
commands you give.
4.5) How do you remove a column from a table?
@ -664,20 +642,14 @@
These are the limits:
Maximum size for a database? unlimited (60GB databases exist)
Maximum size for a table? unlimited on all operating systems
Maximum size for a row? 8k, configurable to 32k
Maximum number of rows in a table? unlimited
Maximum size for a row? unlimited in 7.1 and later
Maximum number of rows in a table? unlimited
Maximum number of columns in a table? unlimited
Maximum number of indexes on a table? unlimited
Of course, these are not actually unlimited, but limited to available
disk space.
To change the maximum row size, edit include/config.h and change
BLCKSZ. To use attributes larger than 8K, you can also use the large
object interface.
The row length limit will be removed in 7.1.
4.7) How much database disk space is required to store data from a typical
text file?
@ -969,10 +941,10 @@ SELECT *
4.24) How do I do an outer join?
PostgreSQL does not support outer joins in the current release. They
can be simulated using UNION and NOT IN. For example, when joining
tab1 and tab2, the following query does an outer join of the two
tables:
PostgreSQL 7.1 and later supports outer joins. In previous releases,
outer joins can be simulated using UNION and NOT IN. For example, when
joining tab1 and tab2, the following query does an outer join of the
two tables:
SELECT tab1.col1, tab2.col2
FROM tab1, tab2
WHERE tab1.col1 = tab2.col1
@ -1011,4 +983,6 @@ SELECT *
change?
The Makefiles do not have the proper dependencies for include files.
You have to do a make clean and then another make.
You have to do a make clean and then another make. If you are using
GCC you can use the --enable-depend option of configure to have the
compiler compute the dependencies automatically.

112
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@ -63,30 +63,27 @@
<CENTER>
<H2>Administrative Questions</H2>
</CENTER>
<A href="#3.1">3.1</A>) Why does <I>initdb</I> fail?<BR>
<A href="#3.2">3.2</A>) How do I install PostgreSQL somewhere
<A href="#3.1">3.1</A>) How do I install PostgreSQL somewhere
other than <I>/usr/local/pgsql?</I><BR>
<A href="#3.3">3.3</A>) When I start the <I>postmaster</I>, I get
<A href="#3.2">3.2</A>) When I start the <I>postmaster</I>, I get
a <I>Bad System Call</I> or core dumped message. Why?<BR>
<A href="#3.4">3.4</A>) When I try to start the <I>postmaster</I>,
<A href="#3.3">3.3</A>) When I try to start the <I>postmaster</I>,
I get <I>IpcMemoryCreate</I> errors. Why?<BR>
<A href="#3.5">3.5</A>) When I try to start the <I>postmaster</I>,
<A href="#3.4">3.4</A>) When I try to start the <I>postmaster</I>,
I get <I>IpcSemaphoreCreate</I> errors. Why?<BR>
<A href="#3.6">3.6</A>) How do I prevent other hosts from
<A href="#3.5">3.5</A>) How do I prevent other hosts from
accessing my PostgreSQL database?<BR>
<A href="#3.7">3.7</A>) Why can't I connect to my database from
<A href="#3.6">3.6</A>) Why can't I connect to my database from
another machine?<BR>
<A href="#3.8">3.8</A>) Why can't I access the database as the
<I>root</I> user?<BR>
<A href="#3.9">3.9</A>) All my servers crash under concurrent
<A href="#3.7">3.7</A>) All my servers crash under concurrent
table access. Why?<BR>
<A href="#3.10">3.10</A>) How do I tune the database engine for
<A href="#3.8">3.8</A>) How do I tune the database engine for
better performance?<BR>
<A href="#3.11">3.11</A>) What debugging features are
<A href="#3.9">3.9</A>) What debugging features are
available?<BR>
<A href="#3.12">3.12</A>) I get <I>"Sorry, too many clients"</I>
<A href="#3.10">3.10</A>) I get <I>"Sorry, too many clients"</I>
when trying to connect. Why?<BR>
<A href="#3.13">3.13</A>) What are the <I>pg_sorttempNNN.NN</I>
<A href="#3.11">3.11</A>) What are the <I>pg_sorttempNNN.NN</I>
files in my database directory?<BR>
@ -236,15 +233,14 @@
other interfaces and binaries to run on MS Windows platforms. In
this case, the client is running on MS Windows, and communicates
via TCP/IP to a server running on one of our supported Unix
platforms.</P>
<P>A file <I>win31.mak</I> is included in the distribution for
platforms. A file <I>win31.mak</I> is included in the distribution for
making a Win32 <I>libpq</I> library and psql.</P>
<P>The database server is now working on Windows NT using Cygwin,
the Cygnus Unix/NT porting library. See <I>pgsql/doc/FAQ_NT</I> in
the distribution. It does not work on MS Windows 9X because Cygwin
does not support the features we need on those platforms.</P>
<P>The database server can run on Windows NT and later using
Cygwin, the Cygnus Unix/NT porting library. See <I>pgsql/doc/FAQ_MSWIN</I>
in the distribution. The database server does not run on MS Windows 9X
because Cygwin does not support the required features on those platforms.
We have no plans to do a native port to any Microsoft platform.</P>
<H4><A name="1.5">1.5</A>) Where can I get PostgreSQL?</H4>
@ -317,7 +313,7 @@
<H4><A name="1.7">1.7</A>) What is the latest release?</H4>
<P>The latest release of PostgreSQL is version 7.0.2.</P>
<P>The latest release of PostgreSQL is version 7.0.3.</P>
<P>We plan to have major releases every four months.</P>
@ -565,39 +561,19 @@
<H2>Administrative Questions</H2>
</CENTER>
<H4><A name="3.1">3.1</A>) Why does <I>initdb</I> fail?</H4>
<P>Try these:</P>
<UL>
<LI>check that you don't have any of the previous version's
binaries in your path</LI>
<LI>check to see that you have the proper paths set</LI>
<LI>check that the <I>postgres</I> user owns the proper
files</LI>
</UL>
<P>If you see an error message about <I>oidvector,</I> you
definately have a version mismatch.</P>
<H4><A name="3.2">3.2</A>) How do I install PostgreSQL somewhere
<H4><A name="3.1">3.1</A>) How do I install PostgreSQL somewhere
other than <I>/usr/local/pgsql?</I></H4>
<P>The simplest way is to specify the --prefix option when running
<I>configure.</I> If you forgot to do that, you can edit
<I>Makefile.global</I> and change POSTGRESDIR accordingly, or
create a <I>Makefile.custom</I> and define POSTGRESDIR there.</P>
<P>Specify the <I>--prefix</I> option when running <I>configure.</I></P>
<H4><A name="3.3">3.3</A>) When I start the <I>postmaster</I>, I
<H4><A name="3.2">3.2</A>) When I start the <I>postmaster</I>, I
get a <I>Bad System Call</I> or core dumped message. Why?</H4>
<P>It could be a variety of problems, but first check to see that
you have System V extensions installed in your kernel. PostgreSQL
requires kernel support for shared memory and semaphores.</P>
<H4><A name="3.4">3.4</A>) When I try to start the
<H4><A name="3.3">3.3</A>) When I try to start the
<I>postmaster,</I> I get <I>IpcMemoryCreate</I> errors. Why?</H4>
<P>You either do not have shared memory configured properly in your
@ -607,7 +583,7 @@
<I>postmaster.</I> For most systems, with default numbers of
buffers and processes, you need a minimum of ~1MB.</P>
<H4><A name="3.5">3.5</A>) When I try to start the
<H4><A name="3.4">3.4</A>) When I try to start the
<I>postmaster,</I> I get <I>IpcSemaphoreCreate</I> errors.
Why?</H4>
@ -623,7 +599,7 @@
<P>If the error message is something else, you might not have
semaphore support configured in your kernel at all.</P>
<H4><A name="3.6">3.6</A>) How do I prevent other hosts from
<H4><A name="3.5">3.5</A>) How do I prevent other hosts from
accessing my PostgreSQL database?</H4>
<P>By default, PostgreSQL only allows connections from the local
@ -633,7 +609,7 @@
modifying the file <I>$PGDATA/pg_hba.conf</I> accordingly. This
will allow TCP/IP connections.</P>
<H4><A name="3.7">3.7</A>) Why can't I connect to my database from
<H4><A name="3.6">3.6</A>) Why can't I connect to my database from
another machine?</H4>
<P>The default configuration allows only unix domain socket
@ -642,21 +618,13 @@
option, and add an appropriate host entry to the file
<I>pgsql/data/pg_hba.conf</I>.</P>
<H4><A name="3.8">3.8</A>) Why can't I access the database as the
<I>root</I> user?</H4>
<P>You should not create database users with user id 0 (root). They
will be unable to access the database. This is a security
precaution because of the ability of users to dynamically link
object modules into the database engine.</P>
<H4><A name="3.9">3.9</A>) All my servers crash under concurrent
<H4><A name="3.7">3.7</A>) All my servers crash under concurrent
table access. Why?</H4>
<P>This problem can be caused by a kernel that is not configured to
support semaphores.</P>
<H4><A name="3.10">3.10</A>) How do I tune the database engine for
<H4><A name="3.8">3.8</A>) How do I tune the database engine for
better performance?</H4>
<P>Certainly, indices can speed up queries. The
@ -693,7 +661,7 @@
data in tables to match an index. See the <SMALL>CLUSTER</SMALL>
manual page for more details.</P>
<H4><A name="3.11">3.11</A>) What debugging features are
<H4><A name="3.9">3.9</A>) What debugging features are
available?</H4>
<P>PostgreSQL has several features that report status information
@ -749,7 +717,7 @@
in the <I>pgsql/data/base/dbname</I> directory. The client profile
file will be put in the client's current directory.</P>
<H4><A name="3.12">3.12</A>) I get 'Sorry, too many clients' when
<H4><A name="3.10">3.10</A>) I get 'Sorry, too many clients' when
trying to connect. Why?</H4>
<P>You need to increase the <I>postmaster's</I> limit on how many
@ -784,7 +752,7 @@
the MaxBackendId constant in
<I>include/storage/sinvaladt.h.</I></P>
<H4><A name="3.13">3.13</A>) What are the <I>pg_sorttempNNN.NN</I>
<H4><A name="3.11">3.11</A>) What are the <I>pg_sorttempNNN.NN</I>
files in my database directory?</H4>
<P>They are temporary files generated by the query executor. For
@ -835,7 +803,7 @@
</H4>
<P>You can read the source code for <I>psql</I> in file
<I>pgsql/src/bin/psql/psql.c.</I> It contains SQL commands that
<I>pgsql/src/bin/psql/describe.c.</I> It contains SQL commands that
generate the output for psql's backslash commands. You can also
start <I>psql</I> with the <I>-E</I> option so it will print out
the queries it uses to execute the commands you give.</P>
@ -860,20 +828,14 @@
<PRE>
Maximum size for a database? unlimited (60GB databases exist)
Maximum size for a table? unlimited on all operating systems
Maximum size for a row? 8k, configurable to 32k
Maximum number of rows in a table? unlimited
Maximum size for a row? unlimited in 7.1 and later
Maximum number of rows in a table? unlimited
Maximum number of columns in a table? unlimited
Maximum number of indexes on a table? unlimited
</PRE>
Of course, these are not actually unlimited, but limited to
available disk space.
<P>To change the maximum row size, edit <I>include/config.h</I> and
change <SMALL>BLCKSZ.</SMALL> To use attributes larger than 8K, you
can also use the large object interface.</P>
<P>The row length limit will be removed in 7.1.</P>
<H4><A name="4.7">4.7</A>) How much database disk space is required
to store data from a typical text file?<BR>
</H4>
@ -1242,8 +1204,8 @@ BYTEA bytea variable-length byte array (null-safe)
<H4><A name="4.24">4.24</A>) How do I do an <I>outer</I> join?<BR>
</H4>
<P>PostgreSQL does not support outer joins in the current release.
They can be simulated using <SMALL>UNION</SMALL> and <SMALL>NOT
<P>PostgreSQL 7.1 and later supports outer joins. In previous releases,
outer joins can be simulated using <SMALL>UNION</SMALL> and <SMALL>NOT
IN</SMALL>. For example, when joining <I>tab1</I> and <I>tab2,</I>
the following query does an <I>outer</I> join of the two
tables:</P>
@ -1295,7 +1257,9 @@ BYTEA bytea variable-length byte array (null-safe)
<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
<I>make</I>.</P>
<I>make</I>. If you are using GCC you can use the <i>--enable-depend</i>
option of <i>configure</i> to have the compiler compute the
dependencies automatically.</P>
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