-==================================================
Frequently Asked Questions (FAQ) for Postgres95
-==================================================
-last updated: Sun Aug 11 01:35:34 EDT 1996
-
-current maintainer: Bruce Momjian (maillist@candle.pha.pa.us)
-original author: Jolly Chen (jolly@cs.berkeley.edu)
-
-changes in this version (* = modified, + = new):
-* 1.8) What documentation is available for 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?
-* 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?
-
-This file is divided approximately as follows:
-1.*) General questions
-2.*) Installation questions
-3.*) Postgres95 Features questions
-4.*) Questions about extending Postgres95
-5.*) Bugs
+
+Last updated: Fri Sep 27 17:48:23 EDT 1996
+Version: 2.0
+
+Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us)
+
+The most recent version of this document can be viewed at the postgres95 Web
+site, http://www.ki.net/postgres95.
+
+Changes in this version (* = modified, + = new):
+
+ * *3.23) How do I create a serial field?
+
+----------------------------------------------------------------------------
Questions answered:
-1.1) What is Postgres95?
-1.2) What does Postgres95 run on?
-1.3) Where can I get Postgres95?
-1.4) What's the copyright on Postgres95?
-1.5) Support for Postgres95
-1.6) Future releases of Postgres95
-1.7) Is there a commercial version of Postgres95?
-1.9) What version of SQL does Postgres95 use?
-1.10) Does Postgres95 work with databases from earlier versions of postgres?
-1.11) How many people use Postgres95?
-2.1) I get the error "cpp: command not found" when I try to compile
-2.2) I get 'yy_flush_buffer undefined' when I try to compile the backend
-2.3) initdb doesn't run
-2.4) when I start up the postmaster, I get
-2.5) The system seems to be confused about commas, decimal points, and
-2.6) How do I install postgres95 somewhere other than /usr/local/postgres95?
-2.7) The backend compiled successfully, but compiling libpq resulted
- in a complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c.
-2.8) Where can I find the bug fixes for postgres95?
-2.9) I can't apply the patches even though everything looks like it should
- work.
-2.10) When I run postmaster, I get a Bad System Call core dumped message.
-2.11) I get the error message "obj/fmgr.h: No such file or directory"
-2.12) When I try to start the postmaster, I get IpcMemoryCreate errors.
-2.13) I get the strange make errors right at the beginning:
-2.14) I have changed a source file, but a recompile does not see the
-3.1) How do I specify a KEY or other constraints on a column?
-3.2) Does Postgres95 support nested subqueries?
-3.3) How do I define a unique indices?
-3.4) I've having a lot of problems with using rules.
-3.5) I can't seem to write into the middle of large objects reliably.
-3.6) Does postgres95 have a graphical user interface? A report
-3.7) How can I write client applications to Postgres95?
-3.8) How do I prevent other hosts from accessing my Postgres95
-3.9) How do I set up a pg_group?
-3.10) What is the exact difference between binary cursors and normal cursors?
-3.11) Why doesn't the != operator work?
-3.12) What is a R-tree index and what is it used for?
-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?
-3.15) Are there ODBC drivers for Postgres95?
-3.16) How do I use postgres for multi-dimensional indexing (> 2 dimensions)?
-3.17) How do I do regular expression searches? case-insensitive
- regexp searching?
-3.18) I can't access the database as the 'root' user.
-3.19) I experienced a server crash during a vacuum. How do I remove the
- lock file?
-3.20) What is the difference between the various character types?
-3.21) In a query, how do I detect if a field is NULL?
-3.22) How do I see how the query optimizer is evaluating my query?
-3.23) How do I create a serial field?
-3.24) How do I create a multi-column index?
-3.25) What are the temp_XXX files in my database directory?
-3.26) Why are my table files not getting any smaller after a delete?
-3.27) Why can't I connect to my database from another machine?
-3.28) I get the error 'default index class unsupported' when creating an
- index. How do I do it?
-3.29) Why does creating an index crash the backend server?
-3.30) How do I specify a decimal constant as a float8, or a string as a text?
-3.31) How do I find out what indexes or operations are defined in the
- 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()'?
-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?
-3.38) How do I tune the database engine for better performace?
-4.1) I wrote a user-defined function and when I run it in psql, it
- dumps core.
-4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0
-4.3) I've written some nifty new types and functions for Postgres95.
-4.4) How do I write a C function to return a tuple?
-5.1) How do I find out about bug fixes?
-5.2) How do I make a bug report?
-
-
-----------------------------------------------------------------------
-Section 1: General Questions
-----------------------------------------------------------------------
-
-1.1) What is Postgres95?
-
- Postgres95 is an enhancement of the POSTGRES database
- management system, a next-generation DBMS research prototype.
- While Postgres95 retains the powerful data model and rich data
- types of POSTGRES, it replaces the PostQuel query language with an
- extended subset of SQL. Postgres95 is free and the complete
- source is available.
-
- Postgres95 development is being performed by a team of Internet
- developers who all subscribe to the Postgres95 development mailing
- list. The current coordinator is Marc G. Fournier (scrappy@ki.net).
- (See below on how to join). This team is now responsible for all
- current and future development of Postgres95.
-
- The authors of Postgres95 1.01 were Andrew Yu and Jolly Chen.
- Many others have contributed to the porting, testing, debugging and
- 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
- working under the direction of Professor Michael Stonebraker
- at the University of California, Berkeley.
-
-1.2) What does Postgres95 run on?
-
- The authors have compiled and tested Postgres95 on the following
- platforms(some of these compiles require gcc 2.7.0):
-
- - DEC Alpha AXP on OSF/1 2.0
- - HP PA-RISC on HP-UX 9.0
- - i386 Solaris
- - SUN SPARC on Solaris 2.4
- - SUN SPARC on SunOS 4.1.3
- - DEC MIPS on Ultrix 4.4
- - Intel x86 on Linux 1.2 and Linux ELF
- - OSs derived from 4.4-lite BSD (NetBSD, FreeBSD)
- - IBM on AIX 3.2.5
- - BSD/OS 2.0, 2.01 & 2.1
- - SGI MIPS on IRIX 5.3
-
- 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
-
-1.4) What's the copyright on Postgres95?
-
- Postgres95 is subject to the following COPYRIGHT.
-
+
+1) General questions
+
+1.1) What is Postgres95?
+1.2) What does Postgres95 run on?
+1.3) Where can I get Postgres95?
+1.4) What's the copyright on Postgres95?
+1.5) Support for Postgres95
+1.6) Latest release of Postgres95
+1.7) Is there a commercial version of Postgres95?
+1.9) What version of SQL does Postgres95 use?
+1.10) Does Postgres95 work with databases from earlier versions of postgres?
+1.11) How many people use Postgres95?
+
+2) Installation questions
+
+2.1) I get the error "cpp: command not found" when I try to compile
+2.2) I get 'yy_flush_buffer undefined' when I try to compile the backend
+2.3) initdb doesn't run
+2.4) when I start up the postmaster, I get
+2.5) The system seems to be confused about commas, decimal points, and date
+formats.
+2.6) How do I install postgres95 somewhere other than /usr/local/postgres95?
+2.7) The backend compiled successfully, but compiling libpq resulted in a
+complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c.
+2.8) Where can I find the bug fixes for postgres95?
+2.9) I can't apply the patches even though everything looks like it should
+work.
+2.10) When I run postmaster, I get a Bad System Call core dumped message.
+2.11) I get the error message "obj/fmgr.h: No such file or directory"
+2.12) When I try to start the postmaster, I get IpcMemoryCreate errors.
+2.13) I get the strange make errors right at the beginning:
+2.14) I have changed a source file, but a recompile does not see the change.
+
+3) Postgres95 Features questions
+
+3.1) How do I specify a KEY or other constraints on a column?
+3.2) Does Postgres95 support nested subqueries?
+3.3) How do I define a unique indices?
+3.4) I've having a lot of problems with using rules.
+3.5) I can't seem to write into the middle of large objects reliably.
+3.6) Does postgres95 have a graphical user interface? A report
+3.7) How can I write client applications to Postgres95?
+3.8) How do I prevent other hosts from accessing my Postgres95
+3.9) How do I set up a pg_group?
+3.10) What is the exact difference between binary cursors and normal
+cursors?
+3.11) Why doesn't the != operator work?
+3.12) What is a R-tree index and what is it used for?
+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?
+3.15) Are there ODBC drivers for Postgres95?
+3.16) How do I use postgres for multi-dimensional indexing (> 2 dimensions)?
+3.17) How do I do regular expression searches? case-insensitive regexp
+searching?
+3.18) I can't access the database as the 'root' user.
+3.19) I experienced a server crash during a vacuum. How do I remove the lock
+file?
+3.20) What is the difference between the various character types?
+3.21) In a query, how do I detect if a field is NULL?
+3.22) How do I see how the query optimizer is evaluating my query?
+3.23) How do I create a serial field?
+3.24) How do I create a multi-column index?
+3.25) What are the temp_XXX files in my database directory?
+3.26) Why are my table files not getting any smaller after a delete?
+3.27) Why can't I connect to my database from another machine?
+3.28) I get the error 'default index class unsupported' when creating an
+index. How do I do it?
+3.29) Why does creating an index crash the backend server?
+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? Why am I getting poor precision?
+3.31) How do I find out what indexes or operations are defined in the
+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()'?
+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?
+3.38) How do I tune the database engine for better performance?
+3.39) What debugging features are available in Postgres95?
+3.40) What is an oid? What is a tid?
+3.41) What is the meaning of some of the terms used in Postgres?
+
+4) Questions about extending Postgres95
+
+4.1) I wrote a user-defined function and when I run it in psql, it dumps
+core.
+4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0
+4.3) I've written some nifty new types and functions for Postgres95.
+4.4) How do I write a C function to return a tuple?
+
+5) Bugs
+
+5.1) How do I find out about bug fixes?
+5.2) How do I make a bug report?
+----------------------------------------------------------------------------
+
+Section 1: General Questions
+
+1.1) What is Postgres95?
+
+Postgres95 is an enhancement of the POSTGRES database management system, a
+next-generation DBMS research prototype. While Postgres95 retains the
+powerful data model and rich data types of POSTGRES, it replaces the
+PostQuel query language with an extended subset of SQL. Postgres95 is free
+and the complete source is available.
+
+Postgres95 development is being performed by a team of Internet developers
+who all subscribe to the Postgres95 development mailing list. The current
+coordinator is Marc G. Fournier (scrappy@ki.net). (See below on how to
+join). This team is now responsible for all current and future development
+of Postgres95.
+
+The authors of Postgres95 1.01 were Andrew Yu and Jolly Chen. Many others
+have contributed to the porting, testing, debugging and 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 working under the direction of Professor Michael Stonebraker at
+the University of California, Berkeley.
+
+1.2) What does Postgres95 run on?
+
+The authors have compiled and tested Postgres95 on the following
+platforms(some of these compiles require gcc 2.7.0):
+
+ * DEC Alpha AXP on OSF/1 2.0
+ * HP PA-RISC on HP-UX 9.0
+ * i386 Solaris
+ * SUN SPARC on Solaris 2.4
+ * SUN SPARC on SunOS 4.1.3
+ * DEC MIPS on Ultrix 4.4
+ * Intel x86 on Linux 1.2 and Linux ELF
+ * OSs derived from 4.4-lite BSD (NetBSD, FreeBSD)
+ * IBM on AIX 3.2.5
+ * BSD/OS 2.0, 2.01 & 2.1
+ * SGI MIPS on IRIX 5.3
+
+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
Copyright (c) 1994-6 Regents of the University of California
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
-LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
-DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE
-POSSIBILITY OF SUCH DAMAGE.
+LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION,
+EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
-INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
-AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
-ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO
+INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN
+"AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO
PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
-1.5) Support for Postgres95
-
- There is no official support for Postgres95 from the original
- maintainers or from University of California, Berkeley. It is
- maintained through volunteer effort only.
-
- With the generosity of the Jason Wright and others at Vnet,
- the postgres95 mailing list now has a new home --
- postgres95@postgres95.vnet.net. It is available for
- discussion of matters pertaining to Postgres95, including but
- not limited to bug reports and fixes. For info on how to
- subscribe, send a mail with the lines in the body (not the
- subject line):
- help
- info postgres95
- to
- majordomo@postgres95.vnet.net
-
- There is also a digest list available. To subscribe to this list,
- send email to majordomo@postgres95.vnet.net with a BODY of:
- subscribe postgres95-digest
- 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
- ftp://postgres95.vnet.net/pub/postgres95/digests
-
- There is also a developers mailing list available. To subscribe to
- this list, send email to pg95-dev-request@ki.net with a BODY of:
-
- subscribe pg95-dev
-
- Additional information about Postgres95 can be found via the
- postgres95 WWW home page at:
- http://www.ki.net/postgres95
+1.5) Support for Postgres95
+
+There is no official support for Postgres95 from the original maintainers or
+from University of California, Berkeley. It is maintained through volunteer
+effort only.
+
+With the generosity of the Jason Wright and others at Vnet, the postgres95
+mailing list now has a new home -- postgres95@postgres95.vnet.net. It is
+available for discussion of matters pertaining to Postgres95, including but
+not limited to bug reports and fixes. For info on how to subscribe, send a
+mail with the lines in the body (not the subject line)
+
+ help
+ info postgres95
+
+to majordomo@postgres95.vnet.net.
+
+There is also a digest list available. To subscribe to this list, send email
+to majordomo@postgres95.vnet.net with a BODY of:
+
+ subscribe postgres95-digest
+
+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
+ * ftp://postgres95.vnet.net/pub/postgres95/digests
+
+There is also a developers mailing list available. To subscribe to this
+list, send email to pg95-dev-request@ki.net with a BODY of:
+
+ subscribe pg95-dev
+
+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
-
- The latest release of postgres95 is version 1.02.
+Section 3: Postgres95 Features
-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
+3.1) How do I specify a KEY or other constraints on a column?
-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
- are included in the distribution. The www page contains
- pointers to an implementation guide and five papers written
- about postgres design concepts and features.
+3.2) Does Postgres95 support nested subqueries?
-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
- 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.
+3.3) How do I define a unique indices?
-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
-----------------------------------------------------------------------
+Postgres95 does not support unique indices. Defining an index does not
+preclude insertion of duplicate index key values.
-2.1) I get the error "cpp: command not found" when I try to compile
-the backend.
+3.4) I've having a lot of problems with using rules.
- Edit the src/backend/utils/Gen_fmgrtab.sh script to include the path
- for the cpp for your particular site.
+Currently, the rule system in postgres95 is mostly broken. It works enough
+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
- has a known bug.
+The Inversion large object system in postgres95 is also mostly broken. It
+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
- * 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..."
+No. No. No. Not in the official distribution at least. Some users have
+reported some success at using 'pgbrowse' and 'onyx' as frontends to
+postgres95. Several contributions are working on tk based frontend tools.
+Ask on the mailing list.
- You probably do not have the right path set up. the 'postgres'
- executable needs to be in your path.
+3.7) How can I write client applications to Postgres95?
-2.5) The system seems to be confused about commas, decimal points, and
-date formats.
+Postgres95 supports a C-callable library interface called libpq as well as a
+Tcl-based library interface called libtcl.
- Check your locale configuration. postgres95 uses the locale
- settings of the user that ran the postmaster process. Set those
- accordingly for your operating environment.
+Others have contributed a perl interface and a WWW gateway to postgres95.
+See the postgres95 home pages for more details.
-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
- your site configuration.
+Use host-based authentication by modifying the file $PGDATA/pg_hba
+accordingly.
-2.7) The backend compiled successfully, but compiling libpq resulted
- in a complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c.
+3.9) How do I set up a pg_group?
- You've probably installed postgres95 somewhere other than
- /usr/local/postgres, but didn't edit the src/Makefile.global
- accordingly. See question 2.6.
+Currently, there is no easy interface to set up user groups. You have to
+explicitly insert/update the pg_group table. For example:
-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
- can be ftp'ed directly from the directory:
- ftp://ftp.ki.net/pub/postgres95
+The fields in pg_group are:
-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.
+ * groname: the group name. This a char16 and should be purely
+ alphanumeric. Do not include underscores or other punctuation.
+ * grosysid: the group id. This is an int4. This should be unique for each
+ group.
+ * grolist: the list of pg_user id's that belong in the group. This is an
+ 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
- have system V extensions installed on your kernel. Postgres95
- requires kernel support for shared memory.
+Normal cursors return data back in ASCII format. Since data is stored
+natively in binary format, the system must do a conversion to produce the
+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"
-
- 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'.
-
-----------------------------------------------------------------------
-Section 3: Postgres95 Features
-----------------------------------------------------------------------
-
-3.1) How do I specify a KEY or other constraints on a column?
-
- Column constraints are not supported in postgres95.
- As a consequence, the system does not check for duplicates.
-
-3.2) Does Postgres95 support nested subqueries?
-
- Subqueries are not implemented, but they can be simulated using sql
- functions.
-
-3.3) How do I define a unique indices?
-
- Postgres95 does not support unique indices. Defining an index does
- not preclude insertion of duplicate index key values.
-
-3.4) I've having a lot of problems with using rules.
-
- Currently, the rule system in postgres95 is mostly broken. It
- works enough to support the view mechanism, but that's about it. Use
- postgres95 rules at your own peril.
-
-3.5) I can't seem to write into the middle of large objects reliably.
-
- The Inversion large object system in postgres95 is also
- mostly broken. It 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.
-
-3.6) Does postgres95 have a graphical user interface? A report
-generator? A embedded query language interface?
-
- No. No. No. Not in the official distribution at least. Some
- users have reported some success at using 'pgbrowse' and 'onyx' as
- frontends to postgres95. Several contributions are working on
- tk based frontend tools. Ask on the mailing list.
-
-3.7) How can I write client applications to Postgres95?
-
- Postgres95 supports a C-callable library interface called libpq
- as well as a Tcl-based library interface called libtcl.
-
- Others have contributed a perl interface and a WWW gateway
- to postgres95. See the postgres95 home pages for more details.
-
-3.8) How do I prevent other hosts from accessing my Postgres95
- backend?
-
- Use host-based authentication by modifying the file
- $PGDATA/pg_hba accordingly.
-
-3.9) How do I set up a pg_group?
-
- Currently, there is no easy interface to set up user groups.
- You have to explicitly insert/update the pg_group table. For example:
-
- 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 fields in pg_group are:
- groname: the group name. This a char16 and should
- be purely alphanumeric. Do not include underscores
- or other punctuation.
- grosysid: the group id. This is an int4.
- This should be unique for each group.
- grolist: the list of pg_user id's that belong in the group.
- This is an int4[].
-
-3.10) What is the exact difference between binary cursors and normal cursors?
-
- Normal cursors return data back in ASCII format. Since data is stored
- natively in binary format, the system must do a conversion to produce
- the 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.
-
- 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 overhead of conversion.
-
- However, ASCII is architectural neutral whereas binary representation
- can differ between different machine architecture. Thus, if your client
- 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
+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
+overhead of conversion.
+
+However, ASCII is architectural neutral whereas binary representation can
+differ between different machine architecture. Thus, if your client 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?
+
+There are two ODBC drivers available, PostODBC and OpenLink ODBC.
+
+For all people being interested in PostODBC, there are now two mailing lists
+devoted to the discussion of PostODBC. The mailing lists are:
+
+ * postodbc-users@listserv.direct. net
+ * postodbc-developers@listse rv.direct.net
+
+these lists are ordinary majordomo mailing lists. You can subscribe by
+sending a mail to:
+
+ * majordomo@listserv.direct.net
+
+OpenLink ODBC is currently in beta under Linux. You can get it from
+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
+platform we support (Win, Mac, Unix, VMS).
+
+We will probably be selling this product to people who need
+commercial-quality support, but a freeware version will always be available.
+Questions to postgres95@openlink.co.uk.
+
+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/)
+
+3.20) What is the difference between the various character types?
+
+Type Internal Name Notes
--------------------------------------------------
-CHAR char 1 character }
-CHAR2 char2 2 characters }
-CHAR4 char4 4 characters } optimized for a fixed length
-CHAR8 char8 8 characters }
-CHAR16 char16 16 characters }
-CHAR(#) bpchar blank padded to the specified fixed length
-VARCHAR(#) varchar size specifies maximum length, no padding
-TEXT text length limited only by maximum tuple length
-BYTEA bytea variable-length array of bytes
-
- Remember, you need to use the internal name when creating indexes
- on these fields or when doing other internal operations.
-
- The last four types above are "varlena" types (i.e. the first
- four bytes is the length, followed by the data). CHAR(#) and
- VARCHAR(#) allocate the maximum number of bytes no matter how
- much data is stored in the field. TEXT and BYTEA are the only
- character types that have variable length on the disk.
-
-3.21) In a query, how do I detect if a field is NULL?
-
- Postgres95 has two builtin keywords, "isnull" and "notnull" (note no
- spaces). For example:
- 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?
-
- Place the word 'EXPLAIN' at the beginning of the query, for example:
-
- EXPLAIN SELECT * FROM table1 WHERE age = 23;
-
-3.23) How do I create a serial field?
-
- There is no way to create a serial or unique field in Postgres95. You
- can use each row's oid field as a unique value. However, if you need
- to dump and reload the database, you will be assigned new oid's.
- There is no way to restore the original oids.
-
- One valid way of doing this is to create a function:
-
- create table my_oids (f1 int4);
- insert into my_oids values (1);
- create function new_oid () returns int4 as
- 'update my_oids set f1 = f1 + 1; select f1 from my_oids; '
- language 'sql';
-
- then:
-
- create table my_stuff (my_key int4, value text);
- insert into my_stuff values (new_oid(), 'hello');
-
- However, keep in mind there is a race condition here where one
- server could do the update, then another one do an update, and
- they both could select the same new id. This statement should
- be performed within a transaction.
-
-3.24) How do I create a multi-column index?
-
- You can not directly create a multi-column index using create index.
- You need to define a function which acts on the multiple columns, then
- use create index with that function.
-
-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 needs to be done to satisfy an ORDER BY, some temp files are
- generated as a result of the sort.
-
- If you have no transactions or sorts running at the time, it is safe to
- delete the temp_ files.
-
-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 are not released. We could move the unused rows to the end of
- the file and use ftruncate() to decrease the file size, but no one has
- implemented this yet.
-
-3.27) Why can't I connect to my database from another machine?
-
- 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.
-
-3.28) I get the error 'default index class unsupported' when creating an
-index. How do I do it?
-
- You probably used:
-
- 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 (called create_index).
-
-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.
-
-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 fail. i.e.:
-
- insert into tab1 values (4.23::float8, '2343'::text)
-
-3.31) How do I find out what indexes or operations are defined in the
+CHAR char 1 character }
+CHAR2 char2 2 characters }
+CHAR4 char4 4 characters } optimized for a fixed length
+CHAR8 char8 8 characters }
+CHAR16 char16 16 characters }
+CHAR(#) bpchar blank padded to the specified fixed length
+VARCHAR(#) varchar size specifies maximum length, no padding
+TEXT text length limited only by maximum tuple length
+BYTEA bytea variable-length array of bytes
+
+Remember, you need to use the internal name when creating indexes on these
+fields or when doing other internal operations.
+
+The last four types above are "varlena" types (i.e. the first four bytes is
+the length, followed by the data). CHAR(#) and VARCHAR(#) allocate the
+maximum number of bytes no matter how much data is stored in the field. TEXT
+and BYTEA are the only character types that have variable length on the
+disk.
+
+3.21) In a query, how do I detect if a field is NULL?
+
+Postgres95 has two builtin keywords, "isnull" and "notnull" (note no
+spaces). Version 1.05 and later and 2.* understand IS NULL and IS NOT NULL.
+
+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:
+
+ EXPLAIN SELECT * FROM table1 WHERE age = 23;
+
+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
+need to dump and reload the database, you need to be using postgres version
+1.07 or 2.* with pgdump's -o option or COPY's WITH OIDS option to preserver
+the oids.
+
+Another valid way of doing this is to create a function:
+
+
+ create table my_oids (f1 int4);
+ insert into my_oids values (1);
+ create function new_oid () returns int4 as
+ 'update my_oids set f1 = f1 + 1; select f1 from my_oids; '
+ language 'sql';
+
+then:
+
+ create table my_stuff (my_key int4, value text);
+ insert into my_stuff values (new_oid(), 'hello');
+
+However, keep in mind there is a race condition here where one server could
+do the update, then another one do an update, and they both could select the
+same new id. This statement should be performed within a transaction.
+
+3.24) How do I create a multi-column index?
+
+You can not directly create a multi-column index using create index. You
+need to define a function which acts on the multiple columns, then use
+create index with that function.
+
+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
+needs to be done to satisfy an ORDER BY, some temp files are generated as a
+result of the sort.
+
+If you have no transactions or sorts running at the time, it is safe to
+delete the temp_ files.
+
+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
+are not released. We could move the unused rows to the end of the file and
+use ftruncate() to decrease the file size, but no one has implemented this
+yet.
+
+3.27) Why can't I connect to my database from another machine?
+
+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.
+
+3.28) I get the error 'default index class unsupported' when creating an
+index. How do I do it?
+
+You probably used:
+
+ 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
+(called create_index). Version 2.0 will correct this deficiency.
+
+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.
+
+3.30) How do I specify a decimal constant as a float8, or a string as a
+text? Why am I getting poor precision?
+
+Use the :: operator. It is needed only when the default promotion rules
+fail. i.e.:
+
+ insert into tab1 values (4.23::float8, '2343'::text)
+
+The default floating-point constant is a float4 in releases prior to 1.05.
+Later releases default to float8.
+
+3.31) How do I find out what indexes or operations are defined in the
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
- 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.
+displays employee rows in the table at the specified time. You can specify
+intervals like [date,date], [date,], [,date], or [,]. This last option
+accesses all rows that ever existed.
- 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
- filter the output of SELECT statements. Unfortunately, this
- PAGER is used even when the standard output is not a terminal.
- 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.
+There are two things that can be done. You can use Openlink's option to
+disable fsync() by starting the postmaster with a '-o -F' option. This will
+prevent fsync()'s from flushing to disk after every transaction.
-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
- 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.
+3.39) What debugging features are available in Postgres95?
-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
- support semaphores.
+First, by compiling with DEBUG defined, many assert()'s monitor the progress
+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
- that is http://www.vex.net/php/
+ cd /usr/local/postgres95
+ ./bin/postmaster >server.log 2>&1 &
- PHP is great for simple stuff, but for more complex stuff, some
- still use the perl interface and CGI.pm.
+This will put a server.log file in the top-level postgres95 directory. This
+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
- tried at:
+You can actuall run the postgres backend from the command line, and type
+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
- 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.
+3.40) What is an oid? What is a tid?
- SELECT *
- FROM employees ['July 24, 1996 09:00:00']
+Oids are Postgres's answer to unique row ids or serial columns. Every row
+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.
- You can specify intervals like [date,date], [date,], [,date],
- or [,]. This last option accesses all rows that ever existed.
+Postgres uses oids in its internal system tables to link rows in separate
+tables. These oids can be used to identify specific user rows and used in
+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
- the table at the desired time will not appear.
+Tids are used to indentify specific physical rows with block and offset
+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
- feature is used by the engine for rollback and crash recovery.
+3.41) What is the meaning of some of the terms used in Postgres?
-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
- option to disable fsync() by starting the postmaster with a
- '-o -F' option. This will prevent fsync()'s from flushing to
- disk after every transaction.
+ * row, record, tuple
+ * attribute, field, column
+ * table, class
+ * retrieve, select
+ * replace, update
+ * oid, serial value
- 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.
+Please let me know if you think of any more.
+----------------------------------------------------------------------------
+Section 4: Extending Postgres95
-----------------------------------------------------------------------
-Section 4: Extending Postgres95
-----------------------------------------------------------------------
+4.1) I wrote a user-defined function and when I run it in psql, it dumps
+core.
-4.1) I wrote a user-defined function and when I run it in psql, it
-dumps core.
+The problem could be a number of things. Try testing your user-defined
+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
- user-defined 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
+4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0 not
+in alloc set!
-4.2) I get messages of the type
- NOTICE:PortalHeapMemoryFree: 0x402251d0 not in alloc set!
+You are pfree'ing something that was not palloc'ed. When writing
+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
- 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.
+4.3) I've written some nifty new types and functions for Postgres95.
- Please share them with other postgres95 users. Send your
- extensions to mailing list, and they will eventually end up in
- the contrib/ subdirectory.
+Please share them with other postgres95 users. Send your extensions to
+mailing list, and they will eventually end up in 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
- have not ever tried it, though in principle it can be done.
- The short answer is ... you can't. This capability is
- forthcoming in the future.
+This requires extreme wizardry, so extreme that the authors have not ever
+tried it, though in principle it can be done. The short answer is ... you
+can't. This capability is 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
- the latest release.
+5.1) How do I find out about bug fixes?
-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
- been fixed (question 5.1). Then, fill out the "bug-template"
- file and send it to:
+5.2) How do I make a bug report?
- 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.