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

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?

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.

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

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

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

unless you add the -i flag to the postmaster, and enable host-based

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

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.

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.

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

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

theoutput 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?

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?

4.24) How do I do an outer join?

PostgreSQLdoes not supportouter 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:

PostgreSQL7.1 and later supportsouter joins. In previous releases,

outer joinscan be simulated using UNION and NOT IN. For example, when

joiningtab1 and tab2, the following query does an outer join of the

twotables:

SELECT tab1.col1, tab2.col2

FROM tab1, tab2

WHERE tab1.col1 = tab2.col1

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.