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==================================================
Frequently Asked Questions (FAQ) for Postgres95 Frequently Asked Questions (FAQ) for Postgres95
==================================================
last updated: Sun Aug 11 01:35:34 EDT 1996 Last updated: Fri Sep 27 17:48:23 EDT 1996
Version: 2.0
current maintainer: Bruce Momjian (maillist@candle.pha.pa.us)
original author: Jolly Chen (jolly@cs.berkeley.edu) Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us)
changes in this version (* = modified, + = new): The most recent version of this document can be viewed at the postgres95 Web
* 1.8) What documentation is available for Postgres95? site, http://www.ki.net/postgres95.
* 3.13) What is the maximum size for a tuple?
* 3.14) I defined indices but my queries don't seem to make use of them. Why? Changes in this version (* = modified, + = new):
* 3.37) What is the time-warp feature and how does it relate to vacuum?
+ 3.38) How do I tune the database engine for better performace? * *3.23) How do I create a serial field?
This file is divided approximately as follows: ----------------------------------------------------------------------------
1.*) General questions
2.*) Installation questions
3.*) Postgres95 Features questions
4.*) Questions about extending Postgres95
5.*) Bugs
Questions answered: Questions answered:
1.1) What is Postgres95?
1.2) What does Postgres95 run on? 1) General questions
1.3) Where can I get Postgres95?
1.4) What's the copyright on Postgres95? 1.1) What is Postgres95?
1.5) Support for Postgres95 1.2) What does Postgres95 run on?
1.6) Future releases of Postgres95 1.3) Where can I get Postgres95?
1.7) Is there a commercial version of Postgres95? 1.4) What's the copyright on Postgres95?
1.9) What version of SQL does Postgres95 use? 1.5) Support for Postgres95
1.10) Does Postgres95 work with databases from earlier versions of postgres? 1.6) Latest release of Postgres95
1.11) How many people use Postgres95? 1.7) Is there a commercial version of Postgres95?
2.1) I get the error "cpp: command not found" when I try to compile 1.9) What version of SQL does Postgres95 use?
2.2) I get 'yy_flush_buffer undefined' when I try to compile the backend 1.10) Does Postgres95 work with databases from earlier versions of postgres?
2.3) initdb doesn't run 1.11) How many people use Postgres95?
2.4) when I start up the postmaster, I get
2.5) The system seems to be confused about commas, decimal points, and 2) Installation questions
2.6) How do I install postgres95 somewhere other than /usr/local/postgres95?
2.7) The backend compiled successfully, but compiling libpq resulted 2.1) I get the error "cpp: command not found" when I try to compile
in a complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c. 2.2) I get 'yy_flush_buffer undefined' when I try to compile the backend
2.8) Where can I find the bug fixes for postgres95? 2.3) initdb doesn't run
2.9) I can't apply the patches even though everything looks like it should 2.4) when I start up the postmaster, I get
work. 2.5) The system seems to be confused about commas, decimal points, and date
2.10) When I run postmaster, I get a Bad System Call core dumped message. formats.
2.11) I get the error message "obj/fmgr.h: No such file or directory" 2.6) How do I install postgres95 somewhere other than /usr/local/postgres95?
2.12) When I try to start the postmaster, I get IpcMemoryCreate errors. 2.7) The backend compiled successfully, but compiling libpq resulted in a
2.13) I get the strange make errors right at the beginning: complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c.
2.14) I have changed a source file, but a recompile does not see the 2.8) Where can I find the bug fixes for postgres95?
3.1) How do I specify a KEY or other constraints on a column? 2.9) I can't apply the patches even though everything looks like it should
3.2) Does Postgres95 support nested subqueries? work.
3.3) How do I define a unique indices? 2.10) When I run postmaster, I get a Bad System Call core dumped message.
3.4) I've having a lot of problems with using rules. 2.11) I get the error message "obj/fmgr.h: No such file or directory"
3.5) I can't seem to write into the middle of large objects reliably. 2.12) When I try to start the postmaster, I get IpcMemoryCreate errors.
3.6) Does postgres95 have a graphical user interface? A report 2.13) I get the strange make errors right at the beginning:
3.7) How can I write client applications to Postgres95? 2.14) I have changed a source file, but a recompile does not see the change.
3.8) How do I prevent other hosts from accessing my Postgres95
3.9) How do I set up a pg_group? 3) Postgres95 Features questions
3.10) What is the exact difference between binary cursors and normal cursors?
3.11) Why doesn't the != operator work? 3.1) How do I specify a KEY or other constraints on a column?
3.12) What is a R-tree index and what is it used for? 3.2) Does Postgres95 support nested subqueries?
3.13) What is the maximum size for a tuple? 3.3) How do I define a unique indices?
3.14) I defined indices but my queries don't seem to make use of them. Why? 3.4) I've having a lot of problems with using rules.
3.15) Are there ODBC drivers for Postgres95? 3.5) I can't seem to write into the middle of large objects reliably.
3.16) How do I use postgres for multi-dimensional indexing (> 2 dimensions)? 3.6) Does postgres95 have a graphical user interface? A report
3.17) How do I do regular expression searches? case-insensitive 3.7) How can I write client applications to Postgres95?
regexp searching? 3.8) How do I prevent other hosts from accessing my Postgres95
3.18) I can't access the database as the 'root' user. 3.9) How do I set up a pg_group?
3.19) I experienced a server crash during a vacuum. How do I remove the 3.10) What is the exact difference between binary cursors and normal
lock file? cursors?
3.20) What is the difference between the various character types? 3.11) Why doesn't the != operator work?
3.21) In a query, how do I detect if a field is NULL? 3.12) What is a R-tree index and what is it used for?
3.22) How do I see how the query optimizer is evaluating my query? 3.13) What is the maximum size for a tuple?
3.23) How do I create a serial field? 3.14) I defined indices but my queries don't seem to make use of them. Why?
3.24) How do I create a multi-column index? 3.15) Are there ODBC drivers for Postgres95?
3.25) What are the temp_XXX files in my database directory? 3.16) How do I use postgres for multi-dimensional indexing (> 2 dimensions)?
3.26) Why are my table files not getting any smaller after a delete? 3.17) How do I do regular expression searches? case-insensitive regexp
3.27) Why can't I connect to my database from another machine? searching?
3.28) I get the error 'default index class unsupported' when creating an 3.18) I can't access the database as the 'root' user.
index. How do I do it? 3.19) I experienced a server crash during a vacuum. How do I remove the lock
3.29) Why does creating an index crash the backend server? file?
3.30) How do I specify a decimal constant as a float8, or a string as a text? 3.20) What is the difference between the various character types?
3.31) How do I find out what indexes or operations are defined in the 3.21) In a query, how do I detect if a field is NULL?
database? 3.22) How do I see how the query optimizer is evaluating my query?
3.32) My database is corrupt. I can't do anything. What should I do? 3.23) How do I create a serial field?
3.33) Createdb, destroydb, createuser,destroyuser don't run. Why? 3.24) How do I create a multi-column index?
3.34) Why does 'createuser' return 'unexpected last match in input()'? 3.25) What are the temp_XXX files in my database directory?
3.35) All my servers crash under concurrent table access. Why? 3.26) Why are my table files not getting any smaller after a delete?
3.36) What tools are available for hooking postgres to Web pages? 3.27) Why can't I connect to my database from another machine?
3.37) What is the time-warp feature and how does it relate to vacuum? 3.28) I get the error 'default index class unsupported' when creating an
3.38) How do I tune the database engine for better performace? index. How do I do it?
4.1) I wrote a user-defined function and when I run it in psql, it 3.29) Why does creating an index crash the backend server?
dumps core. 3.30) How do I specify a decimal constant as a float8, or a string as a
4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0 text? Why am I getting poor precision?
4.3) I've written some nifty new types and functions for Postgres95. 3.30) How do I specify a decimal constant as a float8, or a string as a
4.4) How do I write a C function to return a tuple? text? Why am I getting poor precision?
5.1) How do I find out about bug fixes? 3.31) How do I find out what indexes or operations are defined in the
5.2) How do I make a bug report? database?
3.32) My database is corrupt. I can't do anything. What should I do?
3.33) Createdb, destroydb, createuser,destroyuser don't run. Why?
---------------------------------------------------------------------- 3.34) Why does 'createuser' return 'unexpected last match in input()'?
Section 1: General Questions 3.35) All my servers crash under concurrent table access. Why?
---------------------------------------------------------------------- 3.36) What tools are available for hooking postgres to Web pages?
3.37) What is the time-warp feature and how does it relate to vacuum?
1.1) What is Postgres95? 3.38) How do I tune the database engine for better performance?
3.39) What debugging features are available in Postgres95?
Postgres95 is an enhancement of the POSTGRES database 3.40) What is an oid? What is a tid?
management system, a next-generation DBMS research prototype. 3.41) What is the meaning of some of the terms used in Postgres?
While Postgres95 retains the powerful data model and rich data
types of POSTGRES, it replaces the PostQuel query language with an 4) Questions about extending Postgres95
extended subset of SQL. Postgres95 is free and the complete
source is available. 4.1) I wrote a user-defined function and when I run it in psql, it dumps
core.
Postgres95 development is being performed by a team of Internet 4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0
developers who all subscribe to the Postgres95 development mailing 4.3) I've written some nifty new types and functions for Postgres95.
list. The current coordinator is Marc G. Fournier (scrappy@ki.net). 4.4) How do I write a C function to return a tuple?
(See below on how to join). This team is now responsible for all
current and future development of Postgres95. 5) Bugs
The authors of Postgres95 1.01 were Andrew Yu and Jolly Chen. 5.1) How do I find out about bug fixes?
Many others have contributed to the porting, testing, debugging and 5.2) How do I make a bug report?
enhancement of the code. The original Postgres code, from which ----------------------------------------------------------------------------
Postgres95 is derived, was the effort of many graduate
students, undergraduate students, and staff programmers Section 1: General Questions
working under the direction of Professor Michael Stonebraker
at the University of California, Berkeley. 1.1) What is Postgres95?
1.2) What does Postgres95 run on? Postgres95 is an enhancement of the POSTGRES database management system, a
next-generation DBMS research prototype. While Postgres95 retains the
The authors have compiled and tested Postgres95 on the following powerful data model and rich data types of POSTGRES, it replaces the
platforms(some of these compiles require gcc 2.7.0): PostQuel query language with an extended subset of SQL. Postgres95 is free
and the complete source is available.
- DEC Alpha AXP on OSF/1 2.0
- HP PA-RISC on HP-UX 9.0 Postgres95 development is being performed by a team of Internet developers
- i386 Solaris who all subscribe to the Postgres95 development mailing list. The current
- SUN SPARC on Solaris 2.4 coordinator is Marc G. Fournier (scrappy@ki.net). (See below on how to
- SUN SPARC on SunOS 4.1.3 join). This team is now responsible for all current and future development
- DEC MIPS on Ultrix 4.4 of Postgres95.
- Intel x86 on Linux 1.2 and Linux ELF
- OSs derived from 4.4-lite BSD (NetBSD, FreeBSD) The authors of Postgres95 1.01 were Andrew Yu and Jolly Chen. Many others
- IBM on AIX 3.2.5 have contributed to the porting, testing, debugging and enhancement of the
- BSD/OS 2.0, 2.01 & 2.1 code. The original Postgres code, from which Postgres95 is derived, was the
- SGI MIPS on IRIX 5.3 effort of many graduate students, undergraduate students, and staff
programmers working under the direction of Professor Michael Stonebraker at
The following ports are bundled with the Postgres95 distribution. The the University of California, Berkeley.
authors do not have handy access to these platforms but the
ports have been tested by the others. 1.2) What does Postgres95 run on?
- Motorola MC68K or Intel x86 on NeXTSTEP 3.2 The authors have compiled and tested Postgres95 on the following
- Intel x86 on Intel SVR4 platforms(some of these compiles require gcc 2.7.0):
1.3) Where can I get Postgres95? * DEC Alpha AXP on OSF/1 2.0
* HP PA-RISC on HP-UX 9.0
The primary anonymous ftp site for postgres95 is: * i386 Solaris
* SUN SPARC on Solaris 2.4
ftp://ftp.ki.net/pub/postgres95 * SUN SPARC on SunOS 4.1.3
* DEC MIPS on Ultrix 4.4
A mirror site exists at: * Intel x86 on Linux 1.2 and Linux ELF
* OSs derived from 4.4-lite BSD (NetBSD, FreeBSD)
ftp://postgres95.vnet.net/pub/postgres95 * IBM on AIX 3.2.5
* BSD/OS 2.0, 2.01 & 2.1
1.4) What's the copyright on Postgres95? * SGI MIPS on IRIX 5.3
Postgres95 is subject to the following COPYRIGHT. The following ports are bundled with the Postgres95 distribution. The
authors do not have handy access to these platforms but the ports have been
tested by the others.
* Motorola MC68K or Intel x86 on NeXTSTEP 3.2
* Intel x86 on Intel SVR4
1.3) Where can I get Postgres95?
The primary anonymous ftp site for postgres95 is:
* ftp://ftp.ki.net/pub/postgres95
A mirror site exists at:
* ftp://postgres95.vnet.net/pub/postgres95
* ftp://ftp.luga.or.at/pub/postgres95
* ftp://cal011111.student.utwente.nl/pub/postgres95
1.4) What's the copyright on Postgres95?
Postgres95 is subject to the following COPYRIGHT.
POSTGRES95 Data Base Management System POSTGRES95 Data Base Management System
Copyright (c) 1994-6 Regents of the University of California Copyright (c) 1994-6 Regents of the University of California
...@@ -174,654 +189,717 @@ paragraph and the following two paragraphs appear in all copies. ...@@ -174,654 +189,717 @@ paragraph and the following two paragraphs appear in all copies.
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION,
DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
POSSIBILITY OF SUCH DAMAGE. SUCH DAMAGE.
THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN
ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO
PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
1.5) Support for Postgres95 1.5) Support for Postgres95
There is no official support for Postgres95 from the original There is no official support for Postgres95 from the original maintainers or
maintainers or from University of California, Berkeley. It is from University of California, Berkeley. It is maintained through volunteer
maintained through volunteer effort only. effort only.
With the generosity of the Jason Wright and others at Vnet, With the generosity of the Jason Wright and others at Vnet, the postgres95
the postgres95 mailing list now has a new home -- mailing list now has a new home -- postgres95@postgres95.vnet.net. It is
postgres95@postgres95.vnet.net. It is available for available for discussion of matters pertaining to Postgres95, including but
discussion of matters pertaining to Postgres95, including but not limited to bug reports and fixes. For info on how to subscribe, send a
not limited to bug reports and fixes. For info on how to mail with the lines in the body (not the subject line)
subscribe, send a mail with the lines in the body (not the
subject line): help
help info postgres95
info postgres95
to to majordomo@postgres95.vnet.net.
majordomo@postgres95.vnet.net
There is also a digest list available. To subscribe to this list, send email
There is also a digest list available. To subscribe to this list, to majordomo@postgres95.vnet.net with a BODY of:
send email to majordomo@postgres95.vnet.net with a BODY of:
subscribe postgres95-digest subscribe postgres95-digest
Digests are sent out to members of this list whenever the main list has
received around 30k of messages. Digests are sent out to members of this list whenever the main list has
received around 30k of messages.
Archives and digests of the new mailing list at Vnet can be found at:
ftp://postgres95.vnet.net/pub/postgres95/archives Archives and digests of the new mailing list at Vnet can be found at:
ftp://postgres95.vnet.net/pub/postgres95/digests
* ftp://postgres95.vnet.net/pub/postgres95/archives
There is also a developers mailing list available. To subscribe to * ftp://postgres95.vnet.net/pub/postgres95/digests
this list, send email to pg95-dev-request@ki.net with a BODY of:
There is also a developers mailing list available. To subscribe to this
subscribe pg95-dev list, send email to pg95-dev-request@ki.net with a BODY of:
Additional information about Postgres95 can be found via the subscribe pg95-dev
postgres95 WWW home page at:
http://www.ki.net/postgres95 Additional information about Postgres95 can be found via the postgres95 WWW
home page at:
http://www.ki.net/postgres95
1.6) Latest release of Postgres95
The latest release of postgres95 is version 1.07.
1.7) Is there a commercial version of Postgres95?
Illustra Information Technology (a wholly owned subsidiary of Informix
Software, Inc.) sells an object-relational DBMS called Illustra that was
originally based on postgres. Illustra has cosmetic similarities to
postgres95 but has more features, is more robust, performs better, and
offers real documentation and support. On the flip side, it costs money. For
more information, contact sales@illustra.com
1.8) What documentation is available for Postgres95?
A user manual, manual pages, and some small test examples are included in
the distribution. The sql and built-in manual pages are particularly
important.
The www page contains pointers to an implementation guide and five papers
written about postgres design concepts and features.
1.9) What version of SQL does Postgres95 use?
Postgres95 supports a subset of SQL-92. It has most of the important
constructs but lacks some of the functionality. The most visible differences
are:
* no support for primary keys or column constraints
* no support for nested subqueries
* no HAVING clause under a GROUP BY
On the other hand, you get to create user-defined types, functions,
inheritance etc. If you're willing to help with postgres95 coding,
eventually we can also add the missing features listed above.
1.10) Does Postgres95 work with databases from earlier versions of postgres?
Postgres95 v1.07 is compatible with databases created with v1.01. Those
upgrading from 1.0 should read the directions in the MIGRATION_1.0_TO_1.02
directory.
1.11) How many people use Postgres95?
Since we don't have any licensing or registration scheme, it's impossible to
tell. We do know hundreds copies of postgres95 v1.* have been downloaded,
and that there many hundreds of subscribers to the mailing lists.
----------------------------------------------------------------------------
Section 2: Installation Questions
2.1) I get the error "cpp: command not found" when I try to compile the
backend.
Edit the src/backend/utils/Gen_fmgrtab.sh script to include the path for the
cpp for your particular site.
2.2) I get 'yy_flush_buffer undefined' when I try to compile the backend
Use a more recent version of flex, version 2.5.2. Version 2.5.3 has a known
bug.
2.3) initdb doesn't run
* check to see that you have the proper paths set
* check that the 'postgres' user owns all the right files
* ensure that there are files in $PGDATA/files, and that they are
non-empty. If they aren't, then "gmake install" failed for some reason
2.4) when I start up the postmaster, I get "FindBackend: could not find a
backend to execute..." "postmaster: could not find backend to execute..."
You probably do not have the right path set up. The 'postgres' executable
needs to be in your path.
2.5) The system seems to be confused about commas, decimal points, and date
formats.
Check your locale configuration. postgres95 uses the locale settings of the
user that ran the postmaster process. Set those accordingly for your
operating environment.
2.6) How do I install postgres95 somewhere other than /usr/local/postgres95?
You need to manually edit the paths in src/Makefile.global to your site
configuration.
2.7) The backend compiled successfully, but compiling libpq resulted in a
complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c.
You've probably installed postgres95 somewhere other than
/usr/local/postgres, but didn't edit the src/Makefile.global accordingly.
See question 2.6.
2.8) Where can I find the bug fixes for postgres95?
The patches should be applied in the order listed. The patch files can be
ftp'ed directly from the directory:
* ftp://ftp.ki.net/pub/postgres95
2.9) I can't apply the patches even though everything looks like it should
work.
If you cut and paste directly off your web browser, tabs and whitespaces may
not be preserved properly. Use the 'save as file' option from your web
browser instead.
2.10) When I run postmaster, I get a Bad System Call core dumped message.
It could be a variety of problems, but first check to see that you have
system V extensions installed on your kernel. Postgres95 requires kernel
support for shared memory.
2.11) I get the error message "obj/fmgr.h: No such file or directory"
This indicates that you did not generate the file fmgr.h properly. Something
failed in the running of the src/backend/utils/Gen_fmgrtab.sh script. Check
to see the paths used in that script is appropriate to your system.
2.12) When I try to start the postmaster, I get IpcMemoryCreate errors.
You either do not have shared memory configured properly in kernel or you
need to enlarge the shared memory available in the kernel. The exact amount
you need depends on your architecture and how many buffers you configure
postmaster to run with. For most systems, with default buffer sizes, you
need a minimum of ~760K.
2.13) I get the strange make errors right at the beginning:
warning: NUL character seen; rest of line ignored
*** missing separator. Stop.
or
Is a directory. Stop.
Eliminate any whitespaces at the end of the PORTNAME line in
Makefile.global. Extraneous tabs or spaces will confuse the make templates.
2.14) I have changed a source file, but a recompile does not see the change?
The Makefiles do not have the proper dependencies. You have to do a 'make
clean' and then another 'make'.
----------------------------------------------------------------------------
1.6) Future releases of Postgres95 Section 3: Postgres95 Features
The latest release of postgres95 is version 1.02.
1.7) Is there a commercial version of Postgres95? 3.1) How do I specify a KEY or other constraints on a column?
Illustra Information Technology (a wholly owned subsidiary of
Informix Software, Inc.) sells an object-relational
DBMS called Illustra that was originally based on postgres.
Illustra has cosmetic similarities to postgres95 but has more
features, is more robust, performs better, and offers real
documentation and support. On the flip side, it costs money.
For more information, contact sales@illustra.com
1.8) What documentation is available for Postgres95? Column constraints are not supported in postgres95. As a consequence, the
system does not check for duplicates.
A user manual, manual pages, and some small test examples 3.2) Does Postgres95 support nested subqueries?
are included in the distribution. The www page contains
pointers to an implementation guide and five papers written
about postgres design concepts and features.
1.9) What version of SQL does Postgres95 use? Subqueries are not implemented, but they can be simulated using sql
functions.
Postgres95 supports a subset of SQL-92. It has most of the 3.3) How do I define a unique indices?
important constructs but lacks some of the functionality.
The most visible differences are:
- no support for primary keys or column constraints
- no support for nested subqueries
- no HAVING clause under a GROUP BY
On the other hand, you get to create user-defined types,
functions, inheritance etc. If you're willing to help with
postgres95 coding, eventually we can also add the missing
features listed above.
1.10) Does Postgres95 work with databases from earlier versions of postgres?
Postgres95 v1.02 is compatible with databases created with v1.01.
Those upgrading from 1.0 to 1.02 should read the directions in the
MIGRATION_1.0_TO_1.02 directory.
1.11) How many people use Postgres95? Postgres95 does not support unique indices. Defining an index does not
preclude insertion of duplicate index key values.
Since we don't have any licensing or registration scheme, it's
impossible to tell. We do know hundreds copies of postgres95
v1.* have been downloaded, and that there many hundreds of
subscribers to the mailing lists.
----------------------------------------------------------------------
Section 2: Installation Questions
----------------------------------------------------------------------
2.1) I get the error "cpp: command not found" when I try to compile 3.4) I've having a lot of problems with using rules.
the backend.
Edit the src/backend/utils/Gen_fmgrtab.sh script to include the path Currently, the rule system in postgres95 is mostly broken. It works enough
for the cpp for your particular site. to support the view mechanism, but that's about it. Use postgres95 rules at
your own peril.
2.2) I get 'yy_flush_buffer undefined' when I try to compile the backend 3.5) I can't seem to write into the middle of large objects reliably.
Use a more recent version of flex, version 2.5.2. Version 2.5.3 The Inversion large object system in postgres95 is also mostly broken. It
has a known bug. works well enough for storing large wads of data and reading them back out,
but the implementation has some underlying problems. Use postgres95 large
objects at your own peril.
2.3) initdb doesn't run 3.6) Does postgres95 have a graphical user interface? A report generator? A
embedded query language interface?
* check to see that you have the proper paths set No. No. No. Not in the official distribution at least. Some users have
* check that the 'postgres' user owns all the right files reported some success at using 'pgbrowse' and 'onyx' as frontends to
* ensure that there are files in $PGDATA/files, and that they postgres95. Several contributions are working on tk based frontend tools.
are non-empty. If they aren't, then "gmake install" failed for Ask on the mailing list.
some reason
2.4) when I start up the postmaster, I get
"FindBackend: could not find a backend to execute..."
"postmaster: could not find backend to execute..."
You probably do not have the right path set up. the 'postgres' 3.7) How can I write client applications to Postgres95?
executable needs to be in your path.
2.5) The system seems to be confused about commas, decimal points, and Postgres95 supports a C-callable library interface called libpq as well as a
date formats. Tcl-based library interface called libtcl.
Check your locale configuration. postgres95 uses the locale Others have contributed a perl interface and a WWW gateway to postgres95.
settings of the user that ran the postmaster process. Set those See the postgres95 home pages for more details.
accordingly for your operating environment.
2.6) How do I install postgres95 somewhere other than /usr/local/postgres95? 3.8) How do I prevent other hosts from accessing my Postgres95 backend?
You need to manually edit the paths in src/Makefile.global to Use host-based authentication by modifying the file $PGDATA/pg_hba
your site configuration. accordingly.
2.7) The backend compiled successfully, but compiling libpq resulted 3.9) How do I set up a pg_group?
in a complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c.
You've probably installed postgres95 somewhere other than Currently, there is no easy interface to set up user groups. You have to
/usr/local/postgres, but didn't edit the src/Makefile.global explicitly insert/update the pg_group table. For example:
accordingly. See question 2.6.
2.8) Where can I find the bug fixes for postgres95? jolly=> insert into pg_group (groname, grosysid, grolist)
jolly=> values ('posthackers', '1234', '{5443, 8261}');
INSERT 548224
jolly=> grant insert on foo to group posthackers;
CHANGE
jolly=>
The patches should be applied in the order listed. The patch files The fields in pg_group are:
can be ftp'ed directly from the directory:
ftp://ftp.ki.net/pub/postgres95
2.9) I can't apply the patches even though everything looks like it should * groname: the group name. This a char16 and should be purely
work. alphanumeric. Do not include underscores or other punctuation.
* grosysid: the group id. This is an int4. This should be unique for each
If you cut and paste directly off your web browser, tabs and group.
whitespaces may not be preserved properly. Use the 'save as file' * grolist: the list of pg_user id's that belong in the group. This is an
option from your web browser instead. int4[].
2.10) When I run postmaster, I get a Bad System Call core dumped message. 3.10) What is the exact difference between binary cursors and normal
cursors?
It could be a variety of problems, but first check to see that you Normal cursors return data back in ASCII format. Since data is stored
have system V extensions installed on your kernel. Postgres95 natively in binary format, the system must do a conversion to produce the
requires kernel support for shared memory. ASCII format. In addition, ASCII formats are often large in size than binary
format. Once the attributes come back in ASCII, often the client application
then has to convert it to a binary format to manipulate it anyway.
2.11) I get the error message "obj/fmgr.h: No such file or directory" Binary cursors give you back the data in the native binary representation.
Thus, binary cursors will tend to be a little faster since there's less
This indicates that you did not generate the file fmgr.h overhead of conversion.
properly. Something failed in the running of the
src/backend/utils/Gen_fmgrtab.sh script. Check to see the However, ASCII is architectural neutral whereas binary representation can
paths used in that script is appropriate to your system. differ between different machine architecture. Thus, if your client machine
uses a different representation than you server machine, getting back
2.12) When I try to start the postmaster, I get IpcMemoryCreate errors. attributes in binary format is probably not what you want. Also, if your
main purpose is displaying the data in ASCII, then getting it back in ASCII
You either do not have shared memory configured properly in kernel will save you some effort on the client side.
or you need to enlarge the shared memory available in the kernel.
The exact amount you need depends on your architecture and how 3.11) Why doesn't the != operator work?
many buffers you configure postmaster to run with. For most
systems, with default buffer sizes, you need a minimum of ~760K. SQL specifies <> as the inequality operator, and that is what we have
defined for the built-in types. You are free, however, to extend postgres95
2.13) I get the strange make errors right at the beginning: to include the != operator if you like.
warning: NUL character seen; rest of line ignored
*** missing separator. Stop. 3.12) What is a R-tree index and what is it used for?
or
Is a directory. Stop. An r-tree index is used for indexing spatial data. A hash index can't handle
range searches. A B-tree index only handles range searches in a single
Eliminate any whitespaces at the end of the PORTNAME line in dimension. R-tree's can handle multi-dimensional data. For example, if a
Makefile.global. Extraneous tabs or spaces will confuse the make R-tree index can be built on an attribute of type 'point', the system can
templates. more efficient answer queries like select all points within a bounding
rectangle.
2.14) I have changed a source file, but a recompile does not see the
change? The canonical paper that describes the original R-Tree design is:
The Makefiles do not have the proper dependencies. You have to Guttman, A. "R-Trees: A Dynamic Index Structure for Spatial Searching." Proc
do a 'make clean' and then another 'make'. of the 1984 ACM SIGMOD Int'l Conf on Mgmt of Data, 45-57.
---------------------------------------------------------------------- You can also find this paper in Stonebraker's "Readings in Database Systems"
Section 3: Postgres95 Features
---------------------------------------------------------------------- 3.13) What is the maximum size for a tuple?
3.1) How do I specify a KEY or other constraints on a column? Tuples are limited to 8K bytes. Taking into account system attributes and
other overhead, one should stay well shy of 8,000 bytes to be on the safe
Column constraints are not supported in postgres95. side. To use attributes larger than 8K, try using the large objects
As a consequence, the system does not check for duplicates. interface.
3.2) Does Postgres95 support nested subqueries? Tuples do not cross 8k boundaries so a 5k tuple will require 8k of storage.
Subqueries are not implemented, but they can be simulated using sql 3.14) I defined indices but my queries don't seem to make use of them. Why?
functions.
Postgres95 does not automatically maintain statistics. One has to make an
3.3) How do I define a unique indices? explicit 'vacuum' call to update the statistics. After statistics are
updated, the optimizer has a better shot at using indices. Note that the
Postgres95 does not support unique indices. Defining an index does optimizer is limited and does not use indices in some circumstances (such as
not preclude insertion of duplicate index key values. OR clauses).
3.4) I've having a lot of problems with using rules. If the system still does not see the index, it is probably because you have
created an index on a field with the improper *_ops type. For example, you
Currently, the rule system in postgres95 is mostly broken. It have created a CHAR(4) field, but have specified a char_ops index
works enough to support the view mechanism, but that's about it. Use type_class.
postgres95 rules at your own peril.
See the create_index manual page for information on what type classes are
3.5) I can't seem to write into the middle of large objects reliably. available. It must match the field type.
The Inversion large object system in postgres95 is also Postgres does not warn the user when the improper index is created.
mostly broken. It works well enough for storing large wads
of data and reading them back out, but the implementation has Indexes not used for ORDER BY operations.
some underlying problems. Use postgres95 large objects at
your own peril. 3.15) Are there ODBC drivers for Postgres95?
3.6) Does postgres95 have a graphical user interface? A report There are two ODBC drivers available, PostODBC and OpenLink ODBC.
generator? A embedded query language interface?
For all people being interested in PostODBC, there are now two mailing lists
No. No. No. Not in the official distribution at least. Some devoted to the discussion of PostODBC. The mailing lists are:
users have reported some success at using 'pgbrowse' and 'onyx' as
frontends to postgres95. Several contributions are working on * postodbc-users@listserv.direct. net
tk based frontend tools. Ask on the mailing list. * postodbc-developers@listse rv.direct.net
3.7) How can I write client applications to Postgres95? these lists are ordinary majordomo mailing lists. You can subscribe by
sending a mail to:
Postgres95 supports a C-callable library interface called libpq
as well as a Tcl-based library interface called libtcl. * majordomo@listserv.direct.net
Others have contributed a perl interface and a WWW gateway OpenLink ODBC is currently in beta under Linux. You can get it from
to postgres95. See the postgres95 home pages for more details. http://www.openlinksw.com/postgre s.html. It works with our standard ODBC
client software so you'll have Postgres ODBC available on every client
3.8) How do I prevent other hosts from accessing my Postgres95 platform we support (Win, Mac, Unix, VMS).
backend?
We will probably be selling this product to people who need
Use host-based authentication by modifying the file commercial-quality support, but a freeware version will always be available.
$PGDATA/pg_hba accordingly. Questions to postgres95@openlink.co.uk.
3.9) How do I set up a pg_group? 3.16) How do I use postgres for multi-dimensional indexing (> 2
dimensions">)?
Currently, there is no easy interface to set up user groups.
You have to explicitly insert/update the pg_group table. For example: Builtin R-Trees can handle polygons and boxes. In theory, R-trees can be
extended to handle higher number of dimensions. In practice, extending
jolly=> insert into pg_group (groname, grosysid, grolist) R-trees require a bit of work and we don't currently have any documentation
jolly=> values ('posthackers', '1234', '{5443, 8261}'); on how to do it.
INSERT 548224
jolly=> grant insert on foo to group posthackers; 3.17) How do I do regular expression searches? case-insensitive regexp
CHANGE searching?
jolly=>
Postgres95 supports the SQL LIKE syntax as well as more general regular
The fields in pg_group are: expression searching with the ~ operator. The !~ is the negated regexp
groname: the group name. This a char16 and should operator. ~* and !~* are the case-insensitive regular expression operators.
be purely alphanumeric. Do not include underscores
or other punctuation. 3.18) I can't access the database as the 'root' user.
grosysid: the group id. This is an int4.
This should be unique for each group. You should not create database users with user id 0(root). They will be
grolist: the list of pg_user id's that belong in the group. unable to access the database. This is a security precaution because of the
This is an int4[]. ability of any user to dynamically link object modules into the database
engine.
3.10) What is the exact difference between binary cursors and normal cursors?
3.19) I experienced a server crash during a vacuum. How do I remove the lock
Normal cursors return data back in ASCII format. Since data is stored file?
natively in binary format, the system must do a conversion to produce
the ASCII format. In addition, ASCII formats are often large in size If the server crashes during a vacuum command, chances are it will leave a
than binary format. Once the attributes come back in ASCII, often the lock file hanging around. Attempts to re-run the vacuum command result in
client application then has to convert it to a binary format to
manipulate it anyway. WARN:can't create lock file -- another vacuum cleaner running?
Binary cursors give you back the data in the native binary If you are sure that no vacuum is actually running, you can remove the file
representation. Thus, binary cursors will tend to be a little faster called "pg_vlock" in your database directory (which is $PGDATA/base/)
since there's less overhead of conversion.
3.20) What is the difference between the various character types?
However, ASCII is architectural neutral whereas binary representation
can differ between different machine architecture. Thus, if your client Type Internal Name Notes
machine uses a different representation than you server machine, getting
back attributes in binary format is probably not what you want. Also,
if your main purpose is displaying the data in ASCII, then getting it
back in ASCII will save you some effort on the client side.
3.11) Why doesn't the != operator work?
SQL specifies <> as the inequality operator, and that is what
we have defined for the built-in types. You are free, however, to
extend postgres95 to include the != operator if you like.
3.12) What is a R-tree index and what is it used for?
An r-tree index is used for indexing spatial data. A hash index can't
handle range searches. A B-tree index only handles range searches in a
single dimension. R-tree's can handle multi-dimensional data. For
example, if a R-tree index can be built on an attribute of type
'point', the system can more efficient answer queries like select all
points within a bounding rectangle.
The canonical paper that describes the original R-Tree design is:
Guttman, A. "R-Trees: A Dynamic Index Structure for Spatial Searching."
Proc of the 1984 ACM SIGMOD Int'l Conf on Mgmt of Data, 45-57.
You can also find this paper in Stonebraker's "Readings in Database
Systems"
3.13) What is the maximum size for a tuple?
Tuples are limited to 8K bytes. Taking into account system attributes
and other overhead, one should stay well shy of 8,000 bytes to be on
the safe side. To use attributes larger than 8K, try using the large
objects interface.
Tuples do not cross 8k boundaries so a 5k tuple will require 8k
of storage.
3.14) I defined indices but my queries don't seem to make use of them. Why?
Postgres95 does not automatically maintain statistics. One has to
make an explicit 'vacuum' call to update the statistics. After
statistics are updated, the optimizer has a better shot at using
indices. Note that the optimizer is limited and does not use indices
in some circumstances (such as OR clauses).
If the system still does not see the index, it is probably because you
have created an index on a field with the improper *_ops type. For
example, you have created a CHAR(4) field, but have specified a
char_ops index type_class.
See the create_index manual page for information on what type classes
are available. It must match the field type.
Postgres does not warn the user when the improper index is created.
Indexes not used for ORDER BY operations.
3.15) Are there ODBC drivers for Postgres95?
PostODBC is available as an ODBC driver for Postgres95.
For all people being interested in PostODBC, a freely available ODBC
driver for Postgres95, there are now two mailing lists devoted to the
discussion of PostODBC. The mailing lists are:
postodbc-users@listserv.direct.net
and
postodbc-developers@listserv.direct.net
these lists are ordinary majordomo mailing lists. You can subscribe
by sending a mail to
majordomo@listserv.direct.net
3.16) How do I use postgres for multi-dimensional indexing (> 2 dimensions)?
Builtin R-Trees can handle polygons and boxes. In theory, R-trees can
be extended to handle higher number of dimensions. In practice,
extending R-trees require a bit of work and we don't currently have
any documentation on how to do it.
3.17) How do I do regular expression searches? case-insensitive
regexp searching?
Postgres95 supports the SQL LIKE syntax as well as more general
regular expression searching with the ~ operator. The !~ is the
negated regexp operator. ~* and !~* are the case-insensitive regular
expression operators.
3.18) I can't 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 any user to dynamically link object modules
into the database engine.
3.19) I experienced a server crash during a vacuum. How do I remove the
lock file?
If the server crashes during a vacuum command, chances are it will
leave a lock file hanging around. Attempts to re-run the vacuum
command result in
WARN:can't create lock file -- another vacuum cleaner running?
If you are sure that no vacuum is actually running, you can remove the
file called "pg_vlock" in your database directory (which is
$PGDATA/base/<dbName>)
3.20) What is the difference between the various character types?
Type Internal Name Notes
-------------------------------------------------- --------------------------------------------------
CHAR char 1 character } CHAR char 1 character }
CHAR2 char2 2 characters } CHAR2 char2 2 characters }
CHAR4 char4 4 characters } optimized for a fixed length CHAR4 char4 4 characters } optimized for a fixed length
CHAR8 char8 8 characters } CHAR8 char8 8 characters }
CHAR16 char16 16 characters } CHAR16 char16 16 characters }
CHAR(#) bpchar blank padded to the specified fixed length CHAR(#) bpchar blank padded to the specified fixed length
VARCHAR(#) varchar size specifies maximum length, no padding VARCHAR(#) varchar size specifies maximum length, no padding
TEXT text length limited only by maximum tuple length TEXT text length limited only by maximum tuple length
BYTEA bytea variable-length array of bytes BYTEA bytea variable-length array of bytes
Remember, you need to use the internal name when creating indexes Remember, you need to use the internal name when creating indexes on these
on these fields or when doing other internal operations. fields or when doing other internal operations.
The last four types above are "varlena" types (i.e. the first The last four types above are "varlena" types (i.e. the first four bytes is
four bytes is the length, followed by the data). CHAR(#) and the length, followed by the data). CHAR(#) and VARCHAR(#) allocate the
VARCHAR(#) allocate the maximum number of bytes no matter how maximum number of bytes no matter how much data is stored in the field. TEXT
much data is stored in the field. TEXT and BYTEA are the only and BYTEA are the only character types that have variable length on the
character types that have variable length on the disk. disk.
3.21) In a query, how do I detect if a field is NULL? 3.21) In a query, how do I detect if a field is NULL?
Postgres95 has two builtin keywords, "isnull" and "notnull" (note no Postgres95 has two builtin keywords, "isnull" and "notnull" (note no
spaces). For example: spaces). Version 1.05 and later and 2.* understand IS NULL and IS NOT NULL.
select * from tbl where field isnull
will return rows from tbl where the field is null valued. 3.22) How do I see how the query optimizer is evaluating my query?
3.22) How do I see how the query optimizer is evaluating my query? Place the word 'EXPLAIN' at the beginning of the query, for example:
Place the word 'EXPLAIN' at the beginning of the query, for example: EXPLAIN SELECT * FROM table1 WHERE age = 23;
EXPLAIN SELECT * FROM table1 WHERE age = 23; 3.23) How do I create a serial field?
3.23) How do I create a serial field? Postgres does not allow the user to specifiy a user column as type SERIAL.
Instead, you can use each row's oid field as a unique value. However, if you
There is no way to create a serial or unique field in Postgres95. You need to dump and reload the database, you need to be using postgres version
can use each row's oid field as a unique value. However, if you need 1.07 or 2.* with pgdump's -o option or COPY's WITH OIDS option to preserver
to dump and reload the database, you will be assigned new oid's. the oids.
There is no way to restore the original oids.
Another valid way of doing this is to create a function:
One valid way of doing this is to create a function:
create table my_oids (f1 int4); create table my_oids (f1 int4);
insert into my_oids values (1); insert into my_oids values (1);
create function new_oid () returns int4 as create function new_oid () returns int4 as
'update my_oids set f1 = f1 + 1; select f1 from my_oids; ' 'update my_oids set f1 = f1 + 1; select f1 from my_oids; '
language 'sql'; language 'sql';
then: then:
create table my_stuff (my_key int4, value text); create table my_stuff (my_key int4, value text);
insert into my_stuff values (new_oid(), 'hello'); insert into my_stuff values (new_oid(), 'hello');
However, keep in mind there is a race condition here where one However, keep in mind there is a race condition here where one server could
server could do the update, then another one do an update, and do the update, then another one do an update, and they both could select the
they both could select the same new id. This statement should same new id. This statement should be performed within a transaction.
be performed within a transaction.
3.24) How do I create a multi-column index?
3.24) How do I create a multi-column index?
You can not directly create a multi-column index using create index. You
You can not directly create a multi-column index using create index. need to define a function which acts on the multiple columns, then use
You need to define a function which acts on the multiple columns, then create index with that function.
use create index with that function.
3.25) What are the temp_XXX files in my database directory?
3.25) What are the temp_XXX files in my database directory?
They are temp_ files generated by the query executor. For example, if a sort
They are temp_ files generated by the query executor. For example, needs to be done to satisfy an ORDER BY, some temp files are generated as a
if a sort needs to be done to satisfy an ORDER BY, some temp files are result of the sort.
generated as a result of the sort.
If you have no transactions or sorts running at the time, it is safe to
If you have no transactions or sorts running at the time, it is safe to delete the temp_ files.
delete the temp_ files.
3.26) Why are my table files not getting any smaller after a delete?
3.26) Why are my table files not getting any smaller after a delete?
If you run vacuum, unused rows will be marked for reuse, but the file blocks
If you run vacuum, unused rows will be marked for reuse, but the file are not released. We could move the unused rows to the end of the file and
blocks are not released. We could move the unused rows to the end of use ftruncate() to decrease the file size, but no one has implemented this
the file and use ftruncate() to decrease the file size, but no one has yet.
implemented this yet.
3.27) Why can't I connect to my database from another machine?
3.27) Why can't I connect to my database from another machine?
The default configuration allows only connections from tcp/ip host
The default configuration allows only connections from tcp/ip host localhost. You need to add a host entry to the file postgres95/data/pg_hba.
localhost. You need to add a host entry to the file
postgres95/data/pg_hba. 3.28) I get the error 'default index class unsupported' when creating an
index. How do I do it?
3.28) I get the error 'default index class unsupported' when creating an
index. How do I do it? You probably used:
You probably used: create index idx1 on person using btree (name);
create index idx1 on person using btree (name); Postgres95 indexes are extensible, and therefore you must specify a
class_type when creating an index. Read the manual page for create index
Postgres95 indexes are extensible, and therefore you must specify a (called create_index). Version 2.0 will correct this deficiency.
class_type when creating an index. Read the manual page for create
index (called create_index). 3.29) Why does creating an index crash the backend server?
3.29) Why does creating an index crash the backend server? You have probably defined an incorrect *_ops type class for the field you
are indexing.
You have probably defined an incorrect *_ops type class for the field
you are indexing. 3.30) How do I specify a decimal constant as a float8, or a string as a
text? Why am I getting poor precision?
3.30) How do I specify a decimal constant as a float8, or a string as a text?
Use the :: operator. It is needed only when the default promotion rules
Use the :: operator. It is needed only when the default promotion fail. i.e.:
rules fail. i.e.:
insert into tab1 values (4.23::float8, '2343'::text)
insert into tab1 values (4.23::float8, '2343'::text)
The default floating-point constant is a float4 in releases prior to 1.05.
3.31) How do I find out what indexes or operations are defined in the Later releases default to float8.
3.31) How do I find out what indexes or operations are defined in the
database? database?
Run the file postgres95/src/tutorial/syscat.source. It illustrates
many of the 'select's needed to get information out of the database
system tables.
3.32) My database is corrupt. I can't do anything. What should I do? Run the file postgres95/src/tutorial/syscat.source. It illustrates many of
the 'select's needed to get information out of the database system tables.
3.32) My database is corrupt. I can't do anything. What should I do?
The 1.02 release has a README file and utility that describes a possible
cause of the problem and a workaround. See the file
postgres95/contrib/zap_ltv/README for more information. Also please contact
the README author to help generate a complete fix for this bug.
This bug may be fixed in 1.02.
3.33) Createdb, destroydb, createuser,destroyuser don't run. Why?
Release 1.02 does not have this problem.
The 1.01 release of postgres95 uses a variable called PAGER to filter the
output of SELECT statements. Unfortunately, this PAGER is used even when the
standard output is not a terminal.
3.34) Why does 'createuser' return 'unexpected last match in input(">)'?
You have compile postgres with flex version 2.5.3. There is bug in this
version of flex. Use flex version 2.5.2 instead. There is a doc/README.flex
file which will properly patch the flex 2.5.3 source code.
3.35) All my servers crash under concurrent table access. Why?
This problem can be caused by a kernel that is not configured to support
semaphores.
3.36) What tools are available for hooking postgres to Web pages?
For web integration, PHP/FI is an excellent interface. The URL for that is
http://www.vex.net/php/
PHP is great for simple stuff, but for more complex stuff, some still use
the perl interface and CGI.pm.
An example of using WWW with C to talk to Postgres is can be tried at:
* http://www.ki.net/~mlc
An WWW gatway based on WDB using perl can be downloaded from:
* http://www.eol.ists.ca/~dunlop/wdb -p95
3.37) What is the time-warp feature and how does it relate to vacuum?
Postgres95 handles data changes differently than most database systems. When
a row is changed in a table, the original row is marked with the time it was
changed, and a new row is created with the current data. By default, only
current rows are used in a table. If you specify a date/time after the table
name in a FROM clause, you can access the data that was current at that
time, i.e.
SELECT *
FROM employees ['July 24, 1996 09:00:00']
The 1.02 release has a README file and utility that describes a displays employee rows in the table at the specified time. You can specify
possible cause of the problem and a workaround. See the file intervals like [date,date], [date,], [,date], or [,]. This last option
postgres95/contrib/zap_ltv/README for more information. Also accesses all rows that ever existed.
please contact the README author to help generate a complete
fix for this bug.
This bug may be fixed in 1.02. INSERTed rows get a timestamp too, so rows that were not in the table at the
desired time will not appear.
3.33) Createdb, destroydb, createuser,destroyuser don't run. Why? Vacuum removes rows that are no longer current. This time-warp feature is
used by the engine for rollback and crash recovery.
Release 1.02 does not have this problem. 3.38) How do I tune the database engine for better performance?
The 1.01 release of postgres95 uses a variable called PAGER to There are two things that can be done. You can use Openlink's option to
filter the output of SELECT statements. Unfortunately, this disable fsync() by starting the postmaster with a '-o -F' option. This will
PAGER is used even when the standard output is not a terminal. prevent fsync()'s from flushing to disk after every transaction.
Upgrade to 1.02, due out August 1996, or undefine your PAGER
variable. There is also a patch located in the July archives of
the mailing list that fixes this problem on 1.01.
3.34) Why does 'createuser' return 'unexpected last match in input()'? You can also use the postmaster -B option to increase the number of shared
memory buffers shared among the backend processes. If you make this
parameter too high, the process will not start or crash unexpectedly. Each
buffer is 8K and the defualt is 64 buffers.
You have compile postgres with flex version 2.5.3. There is bug 3.39) What debugging features are available in Postgres95?
in this version of flex. Use flex version 2.5.2 instead. There
is a doc/README.flex file which will properly patch the flex 2.5.3
source code.
3.35) All my servers crash under concurrent table access. Why? Postgres95 has several features that report status information that can be
valuable for debugging purposes.
This problem can be caused by a kernel that is not configured to First, by compiling with DEBUG defined, many assert()'s monitor the progress
support semaphores. of the backend and halt the program when something unexpected occurs.
3.36) What tools are available for hooking postgres to Web pages? Both postmaster and postgres have several debug options available. First,
whenever you start the postmaster, make sure you send the standard output
and error to a log file, like:
For web integration, PHP/FI is an excellent interface. The URL for cd /usr/local/postgres95
that is http://www.vex.net/php/ ./bin/postmaster >server.log 2>&1 &
PHP is great for simple stuff, but for more complex stuff, some This will put a server.log file in the top-level postgres95 directory. This
still use the perl interface and CGI.pm. file can contain useful information about problems or errors encountered by
the server. Postmaster has a -d option that allows even more detailed
information to be reported. The -d option takes a number 1-3 that specifies
the debug level. The query plans in a verbose debug file can be formatted
using the 'indent' program. (You may need to remove the '====' lines.) Be
warned that a debug level greater than one generates large log files.
An example of using WWW with C to talk to Postgres is can be You can actuall run the postgres backend from the command line, and type
tried at: your SQL statement directly. This is recommended ONLY for debugging
purposes. Note that a newline terminates the query, not a semicolon. If you
have compiled with debugging symbols, you can perhaps use a debugger to see
what is happening. Because the backend was not started from the postmaster,
it is not running in an identical environment and locking/backend
interaction problems may not be duplicated. Some operating system can attach
to a running backend directly to diagnose problems.
http://www.ki.net/~mlc The postgres program has a -s, -A, -t options that can be very usefull for
debugging and performance measurements.
3.37) What is the time-warp feature and how does it relate to vacuum? The EXPLAIN command (see this FAQ) allows you to see how postgres95 is
iterpreting your query.
Postgres95 handles data changes differently than most database 3.40) What is an oid? What is a tid?
systems. When a row is changed in a table, the original row
is marked with the time it was changed, and a new row is created
with the current data. By default, only current rows are used
in a table. If you specify a date/time after the table name in
a FROM clause, you can access the data that was current at that
time, i.e.
SELECT * Oids are Postgres's answer to unique row ids or serial columns. Every row
FROM employees ['July 24, 1996 09:00:00'] that is created in Postgres gets a unique oid. All oids generated by initdb
are less than 16384 (from backend/access/transam.h). All post-initdb
(user-created) oids are equal or greater that this. All these oids are
unique not only within a table, or database, but unique within the entire
postgres installation.
displays employee rows in the table at the specified time. Postgres uses oids in its internal system tables to link rows in separate
You can specify intervals like [date,date], [date,], [,date], tables. These oids can be used to identify specific user rows and used in
or [,]. This last option accesses all rows that ever existed. joins. It is recommended you use column type oid to store oid values. See
the sql(l) manual page to see the other internal columns.
INSERTed rows get a timestamp too, so rows that were not in Tids are used to indentify specific physical rows with block and offset
the table at the desired time will not appear. values. Tids change after rows are modified or reloaded. They are used by
index entries to point to physical rows. They can not be accessed through
sql.
Vacuum removes rows that are no longer current. This time-warp 3.41) What is the meaning of some of the terms used in Postgres?
feature is used by the engine for rollback and crash recovery.
3.38) How do I tune the database engine for better performace? Some of the source code and older documentation use terms that have more
common usage. Here are some:
There are two things that can be done. You can use Openlink's * row, record, tuple
option to disable fsync() by starting the postmaster with a * attribute, field, column
'-o -F' option. This will prevent fsync()'s from flushing to * table, class
disk after every transaction. * retrieve, select
* replace, update
* oid, serial value
You can also use the postmaster -B option to increase the number Please let me know if you think of any more.
of shared memory buffers shared among the backend processes. If
you make this parameter too high, the process will not start or
crash unexpectedly. Each buffer is 8K and the defualt is 64
buffers.
----------------------------------------------------------------------------
Section 4: Extending Postgres95
---------------------------------------------------------------------- 4.1) I wrote a user-defined function and when I run it in psql, it dumps
Section 4: Extending Postgres95 core.
----------------------------------------------------------------------
4.1) I wrote a user-defined function and when I run it in psql, it The problem could be a number of things. Try testing your user-defined
dumps core. function in a stand alone test program first. Also, make sure you are not
sending elog NOTICES when the front-end is expecting data, such as during a
type_in() or type_out() functions
The problem could be a number of things. Try testing your 4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0 not
user-defined function in a stand alone test program first. in alloc set!
Also, make sure you are not sending elog NOTICES when the front-end
is expecting data, such as during a type_in() or type_out()
functions
4.2) I get messages of the type You are pfree'ing something that was not palloc'ed. When writing
NOTICE:PortalHeapMemoryFree: 0x402251d0 not in alloc set! user-defined functions, do not include the file "libpq-fe.h". Doing so will
cause your palloc to be a malloc instead of a free. Then, when the backend
pfrees the storage, you get the notice message.
You are pfree'ing something that was not palloc'ed. When writing 4.3) I've written some nifty new types and functions for Postgres95.
user-defined functions, do not include the file
"libpq-fe.h". Doing so will cause your palloc to be a malloc
instead of a free. Then, when the backend pfrees the storage,
you get the notice message.
4.3) I've written some nifty new types and functions for Postgres95.
Please share them with other postgres95 users. Send your Please share them with other postgres95 users. Send your extensions to
extensions to mailing list, and they will eventually end up in mailing list, and they will eventually end up in the contrib/ subdirectory.
the contrib/ subdirectory.
4.4) How do I write a C function to return a tuple? 4.4) How do I write a C function to return a tuple?
This requires extreme wizardry, so extreme that the authors This requires extreme wizardry, so extreme that the authors have not ever
have not ever tried it, though in principle it can be done. tried it, though in principle it can be done. The short answer is ... you
The short answer is ... you can't. This capability is can't. This capability is forthcoming in the future.
forthcoming in the future.
---------------------------------------------------------------------- ----------------------------------------------------------------------------
Section 5: Bugs
----------------------------------------------------------------------
5.1) How do I find out about bug fixes? Section 5: Bugs
The directory ftp.ki.net:/pub/postgres95 contains patches for 5.1) How do I find out about bug fixes?
the latest release.
5.2) How do I make a bug report? The directory ftp://ftp.ki.net/pub/postgres95 contains patches for the
latest release.
First, check to see that your bug is not one that has already 5.2) How do I make a bug report?
been fixed (question 5.1). Then, fill out the "bug-template"
file and send it to:
pg95-dev@ki.net First, check to see that your bug is not one that has already been fixed
(question 5.1). Then, fill out the "bug-template" file and send it to:
This is the address of the developers mailing list. * pg95-dev@ki.net
This is the address of the developers mailing list.
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