From: Bruce Momjian Date: Wed, 18 Feb 1998 15:56:06 +0000 (+0000) Subject: Update FAQ's for release. X-Git-Tag: REL6_3~118 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=fe521fbe761326a03c76291e7a8fd265f3d69277;p=postgresql Update FAQ's for release. --- diff --git a/doc/FAQ b/doc/FAQ index 9277d83fca..45d02f19ac 100644 --- a/doc/FAQ +++ b/doc/FAQ @@ -1,513 +1,503 @@ +Frequently Asked Questions (FAQ) for PostgreSQL + +Last updated: Sun Feb 1 16:13:28 EST 1998 + +Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us) + +The most recent version of this document can be viewed at the postgreSQL Web +site, http://postgreSQL.org. + +Linux-specific questions are answered in +http://postgreSQL.org/docs/faq-linux.shtml. + +Irix-specific questions are answered in +http://postgreSQL.org/docs/faq-irix.shtml. + + ------------------------------------------------------------------------ - Frequently Asked Questions (FAQ) for PostgreSQL - - Last updated: Sun Feb 1 16:13:28 EST 1998 - - Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us) - - The most recent version of this document can be viewed at the - postgreSQL Web site, http://postgreSQL.org. - - Linux-specific questions are answered in - http://postgreSQL.org/docs/FAQ-linux.shtml. - - Irix-specific questions are answered in - http://postgreSQL.org/docs/FAQ-irix.shtml. - _________________________________________________________________ - Questions answered: - 1) General questions - - 1.1) What is PostgreSQL? - 1.2) What does PostgreSQL run on? - 1.3) Where can I get PostgreSQL? - 1.4) What's the copyright on PostgreSQL? - 1.5) Support for PostgreSQL - 1.6) Latest release of PostgreSQL - 1.7) Is there a commercial version of PostgreSQL? - 1.8) What documentation is available for PostgreSQL? - 1.9) What version of SQL does PostgreSQL use? - 1.10) Does PostgreSQL work with databases from earlier versions of - postgres? - 1.11) Are there ODBC drivers for PostgreSQL? - 1.12) What tools are available for hooking postgres to Web pages? - 1.13) Does PostgreSQL have a graphical user interface? A report - generator? A embedded query language interface? - 1.14) What is a good book to learn SQL? - - 2) Installation/Configuration questions - - 2.1) initdb doesn't run - 2.2) when I start up the postmaster, I get "FindBackend: could not - find a backend to execute..." "postmaster: could not find backend to - execute..." - 2.3) The system seems to be confused about commas, decimal points, and - date formats. - 2.4) How do I install PostgreSQL somewhere other than - /usr/local/pgsql? - 2.5) When I run postmaster, I get a Bad System Call core dumped - message. - 2.6) When I try to start the postmaster, I get IpcMemoryCreate errors. - 2.7) I have changed a source file, but a recompile does not see the - change? - 2.8) How do I prevent other hosts from accessing my PostgreSQL - 2.9) I can't access the database as the 'root' user. - 2.10) All my servers crash under concurrent table access. Why? - 2.11) How do I tune the database engine for better performance? - 2.12) What debugging features are available in PostgreSQL? - 2.13) How do I enable more than 32 concurrent backends? - - 3) Operational questions - - 3.1) Does PostgreSQL support nested subqueries? - 3.2) I've having a lot of problems using rules. - 3.3) I can't seem to write into the middle of large objects reliably. - 3.4) How can I write client applications to PostgreSQL? - 3.5) How do I set up a pg_group? - 3.6) What is the exact difference between binary cursors and normal - cursors? - 3.7) What is a R-tree index and what is it used for? - 3.8) What is the maximum size for a tuple? - 3.9) I defined indices but my queries don't seem to make use of them. - Why? - 3.10) How do I do regular expression searches? case-insensitive regexp - searching? - 3.11) I experienced a server crash during a vacuum. How do I remove - the lock file? - 3.12) What is the difference between the various character types? - 3.13) In a query, how do I detect if a field is NULL? - 3.14) How do I see how the query optimizer is evaluating my query? - 3.15) How do I create a serial field? - 3.16) What are the pg_psort.XXX files in my database directory? - 3.17) Why can't I connect to my database from another machine? - 3.18) How do I find out what indexes or operations are defined in the - database? - 3.19) What is the time-warp feature and how does it relate to vacuum? - 3.20) What is an oid? What is a tid? - 3.21) What is the meaning of some of the terms used in Postgres? - 3.22) What is Genetic Query Optimization? - 3.23) How do you remove a column from a table? - 3.24) How do SELECT only the first few rows of a query? - 3.25) Why can't I create a column named "time"? - 3.26) How much database disk space is required to store data from a - typical flat file? - - 4) Questions about extending PostgreSQL - - 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 PostgreSQL. - 4.4) How do I write a C function to return a tuple? - - 5) Bugs - - 5.1) How do I make a bug report? - _________________________________________________________________ - +1) General questions + +1.1) What is PostgreSQL? +1.2) What does PostgreSQL run on? +1.3) Where can I get PostgreSQL? +1.4) What's the copyright on PostgreSQL? +1.5) Support for PostgreSQL +1.6) Latest release of PostgreSQL +1.7) Is there a commercial version of PostgreSQL? +1.8) What documentation is available for PostgreSQL? +1.9) What version of SQL does PostgreSQL use? +1.10) Does PostgreSQL work with databases from earlier versions of postgres? +1.11) Are there ODBC drivers for PostgreSQL? +1.12) What tools are available for hooking postgres to Web pages? +1.13) Does PostgreSQL have a graphical user interface? A report generator? A +embedded query language interface? +1.14) What is a good book to learn SQL? + +2) Installation/Configuration questions + +2.1) initdb doesn't run +2.2) when I start up the postmaster, I get "FindBackend: could not find a +backend to execute..." "postmaster: could not find backend to execute..." +2.3) The system seems to be confused about commas, decimal points, and date +formats. +2.4) How do I install PostgreSQL somewhere other than /usr/local/pgsql? +2.5) When I run postmaster, I get a Bad System Call core dumped message. +2.6) When I try to start the postmaster, I get IpcMemoryCreate errors. +2.7) I have changed a source file, but a recompile does not see the change? +2.8) How do I prevent other hosts from accessing my PostgreSQL +2.9) I can't access the database as the 'root' user. +2.10) All my servers crash under concurrent table access. Why? +2.11) How do I tune the database engine for better performance? +2.12) What debugging features are available in PostgreSQL? +2.13) How do I enable more than 32 concurrent backends? + +3) Operational questions + +3.1) Does PostgreSQL support nested subqueries? +3.2) I've having a lot of problems using rules. +3.3) I can't seem to write into the middle of large objects reliably. +3.4) How can I write client applications to PostgreSQL? +3.5) How do I set up a pg_group? +3.6) What is the exact difference between binary cursors and normal cursors? +3.7) What is a R-tree index and what is it used for? +3.8) What is the maximum size for a tuple? +3.9) I defined indices but my queries don't seem to make use of them. Why? +3.10) How do I do regular expression searches? case-insensitive regexp +searching? +3.11) I experienced a server crash during a vacuum. How do I remove the lock +file? +3.12) What is the difference between the various character types? +3.13) In a query, how do I detect if a field is NULL? +3.14) How do I see how the query optimizer is evaluating my query? +3.15) How do I create a serial field? +3.16) What are the pg_psort.XXX files in my database directory? +3.17) Why can't I connect to my database from another machine? +3.18) How do I find out what indexes or operations are defined in the +database? +3.19) What is the time-warp feature and how does it relate to vacuum? +3.20) What is an oid? What is a tid? +3.21) What is the meaning of some of the terms used in Postgres? +3.22) What is Genetic Query Optimization? +3.23) How do you remove a column from a table? +3.24) How do SELECT only the first few rows of a query? +3.25) Why can't I create a column named "time"? +3.26) How much database disk space is required to store data from a typical +flat file? + +4) Questions about extending PostgreSQL + +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 PostgreSQL. +4.4) How do I write a C function to return a tuple? + +5) Bugs + +5.1) How do I make a bug report? + + ------------------------------------------------------------------------ + Section 1: General Questions - 1.1) What is PostgreSQL? - - PostgreSQL is an enhancement of the POSTGRES database management - system, a next-generation DBMS research prototype. While PostgreSQL - retains the powerful data model and rich data types of POSTGRES, it - replaces the PostQuel query language with an extended subset of SQL. - PostgreSQL is free and the complete source is available. - - PostgreSQL development is being performed by a team of Internet - developers who all subscribe to the PostgreSQL development mailing - list. The current coordinator is Marc G. Fournier - (scrappy@postgreSQL.org). (See below on how to join). This team is now - responsible for all current and future development of PostgreSQL. - - The authors of PostgreSQL 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 - PostgreSQL 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. - - The original name of the software at Berkeley was Postgres. When SQL - functionality was added in 1995, its name was changed to Postgres95. - The name was changed at the end of 1996 to PostgreSQL. - - 1.2) What does PostgreSQL run on? - - The authors have compiled and tested PostgreSQL on the following - platforms(some of these compiles require gcc 2.7.0): - * aix - IBM on AIX 3.2.5 or 4.x - * alpha - DEC Alpha AXP on Digital Unix 2.0, 3.2, 4.0 - * BSD44_derived - OSs derived from 4.4-lite BSD (NetBSD, FreeBSD) - * bsdi - BSD/OS 2.0, 2.01, 2.1, 3.0 - * dgux - DG/UX 5.4R4.11 - * hpux - HP PA-RISC on HP-UX 9.0, 10 - * i386_solaris - i386 Solaris - * irix5 - SGI MIPS on IRIX 5.3 - * linux - Intel x86 on Linux 2.0 and Linux ELF SPARC on Linux ELF - PPC on Linux Elf (For non-ELF Linux, see LINUX_ELF below). - * sco - SCO 3.2v5 - * sparc_solaris - SUN SPARC on Solaris 2.4, 2.5, 2.5.1 - * sunos4 - SUN SPARC on SunOS 4.1.3 - * svr4 - Intel x86 on Intel SVR4 and MIPS - * ultrix4 - DEC MIPS on Ultrix 4.4 - - The following platforms have known problems/bugs: - * nextstep - Motorola MC68K or Intel x86 on NeXTSTEP 3.2 - - 1.3) Where can I get PostgreSQL? - - The primary anonymous ftp site for PostgreSQL is: - * ftp://ftp.postgreSQL.org/pub - - 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 - * ftp://ftp.uni-trier.de/pub/database/rdbms/postgres/postgres95 - * ftp://rocker.sch.bme.hu - - 1.4) What's the copyright on PostgreSQL? - - PostgreSQL is subject to the following COPYRIGHT. - - PostgreSQL Data Base Management System - - Copyright (c) 1994-6 Regents of the University of California - - Permission to use, copy, modify, and distribute this software and its - documentation for any purpose, without fee, and without a written - agreement is hereby granted, provided that the above copyright notice - and this paragraph and the following two paragraphs appear in all - copies. - - 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. - - 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 PROVIDE MAINTENANCE, SUPPORT, - UPDATES, ENHANCEMENTS, OR MODIFICATIONS. - - 1.5) Support for PostgreSQL - - There is no official support for PostgreSQL from the original - maintainers or from University of California, Berkeley. It is - maintained through volunteer effort only. - - The main mailing list is: questions@postgreSQL.org. It is available - for discussion o f matters pertaining to PostgreSQL, 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) +1.1) What is PostgreSQL? + +PostgreSQL is an enhancement of the POSTGRES database management system, a +next-generation DBMS research prototype. While PostgreSQL retains the +powerful data model and rich data types of POSTGRES, it replaces the +PostQuel query language with an extended subset of SQL. PostgreSQL is free +and the complete source is available. + +PostgreSQL development is being performed by a team of Internet developers +who all subscribe to the PostgreSQL development mailing list. The current +coordinator is Marc G. Fournier (scrappy@postgreSQL.org). (See below on how +to join). This team is now responsible for all current and future +development of PostgreSQL. + +The authors of PostgreSQL 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 PostgreSQL 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. + +The original name of the software at Berkeley was Postgres. When SQL +functionality was added in 1995, its name was changed to Postgres95. The +name was changed at the end of 1996 to PostgreSQL. + +1.2) What does PostgreSQL run on? + +The authors have compiled and tested PostgreSQL on the following +platforms(some of these compiles require gcc 2.7.0): + + * aix - IBM on AIX 3.2.5 or 4.x + * alpha - DEC Alpha AXP on Digital Unix 2.0, 3.2, 4.0 + * BSD44_derived - OSs derived from 4.4-lite BSD (NetBSD, FreeBSD) + * bsdi - BSD/OS 2.0, 2.01, 2.1, 3.0 + * dgux - DG/UX 5.4R4.11 + * hpux - HP PA-RISC on HP-UX 9.0, 10 + * i386_solaris - i386 Solaris + * irix5 - SGI MIPS on IRIX 5.3 + * linux - Intel x86 on Linux 2.0 and Linux ELF SPARC on Linux ELF PPC on + Linux Elf (For non-ELF Linux, see LINUX_ELF below). + * sco - SCO 3.2v5 + * sparc_solaris - SUN SPARC on Solaris 2.4, 2.5, 2.5.1 + * sunos4 - SUN SPARC on SunOS 4.1.3 + * svr4 - Intel x86 on Intel SVR4 and MIPS + * ultrix4 - DEC MIPS on Ultrix 4.4 + +The following platforms have known problems/bugs: + + * nextstep - Motorola MC68K or Intel x86 on NeXTSTEP 3.2 + +1.3) Where can I get PostgreSQL? + +The primary anonymous ftp site for PostgreSQL is: + + * ftp://ftp.postgreSQL.org/pub + +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 + * ftp://ftp.uni-trier.de/pub/database/rdbms/postgres/postgres95 + * ftp://rocker.sch.bme.hu + +1.4) What's the copyright on PostgreSQL? + +PostgreSQL is subject to the following COPYRIGHT. + +PostgreSQL Data Base Management System + +Copyright (c) 1994-6 Regents of the University of California +Permission to use, copy, modify, and distribute this software and its +documentation for any purpose, without fee, and without a written agreement +is hereby granted, provided that the above copyright notice and this +paragraph and the following two paragraphs appear in all copies. + +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. + +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 +PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. + +1.5) Support for PostgreSQL + +There is no official support for PostgreSQL from the original maintainers or +from University of California, Berkeley. It is maintained through volunteer +effort only. + +The main mailing list is: questions@postgreSQL.org. It is available for +discussion o f matters pertaining to PostgreSQL, 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) subscribe end - to questions-request@postgreSQL.org. - - There is also a digest list available. To subscribe to this list, send - email to: questions-digest-request@postgreSQL.org with a BODY of: +to questions-request@postgreSQL.org. +There is also a digest list available. To subscribe to this list, send email +to: questions-digest-request@postgreSQL.org with a BODY of: subscribe end - Digests are sent out to members of this list whenever the main list - has received around 30k of messages. - - There is a bugs mailing list available. To subscribe to this list, - send email to bugs-request@postgreSQL.org with a BODY of: - - There is also a developers discussion mailing list available. To - subscribe to this list, send email to hackers-request@postgreSQL.org - with a BODY of: - +Digests are sent out to members of this list whenever the main list has +received around 30k of messages. + +There is a bugs mailing list available. To subscribe to this list, send +email to bugs-request@postgreSQL.org with a BODY of: + +There is also a developers discussion mailing list available. To subscribe +to this list, send email to hackers-request@postgreSQL.org with a BODY of: subscribe end - Additional information about PostgreSQL can be found via the - PostgreSQL WWW home page at: - +Additional information about PostgreSQL can be found via the PostgreSQL WWW +home page at: + http://postgreSQL.org - - 1.6) Latest release of PostgreSQL - - The latest release of PostgreSQL is version 6.2.1, which was released - on October 17th, 1997. We are testing 6.3 beta. For information about - what is new in 6.3, see our TODO list on our WWW page. - - We plan to have major releases every three months. - - 1.7) Is there a commercial version of PostgreSQL? - - 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 PostgreSQL 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 PostgreSQL? - - 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 PostgreSQL use? - - PostgreSQL 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 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 PostgreSQL coding, - eventually we can also add the missing features listed above. - - 1.10) Does PostgreSQL work with databases from earlier versions of postgres? - - PostgreSQL v1.09 is compatible with databases created with v1.01. - - Upgrading to 6.3 from earlier releases requires a dump and restore. - - Upgrading to 6.2.1 from pre-6.2 requires a dump and restore. - - Upgrading to 6.2.1 from 6.2 does not require a dump, but see the - appropriate /migration file in the distribution. - - Those ugrading from versions earlier than 1.09 must upgrade to 1.09 - first without a dump/reload, then dump the data from 1.09, and then - load it into 6.2.1 or 6.3 beta. - - 1.11) Are there ODBC drivers for PostgreSQL? - - 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 very popular. You can get it from - http://www.openlinksw.com/postgres.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. - - 1.12) What tools are available for hooking postgres to Web pages? - - A nice introduction to Database-backed Web pages can be seen at: - http://www.webtools.com - - For web integration, PHP is an excellent interface. The URL for that - is http://php.iquest.net - - PHP is great for simple stuff, but for more complex stuff, some still - use the perl interface and CGI.pm. - - An WWW gatway based on WDB using perl can be downloaded from: - * http://www.eol.ists.ca/~dunlop/wdb -p95 - - 1.13) Does PostgreSQL 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 - PostgreSQL. Several contributions are working on tk based frontend - tools. Ask on the mailing list. - - 1.14) What is a good book to learn SQL? - - Many of our users like The Practical SQL Handbook, Bowman et al, - Addison Wesley. - _________________________________________________________________ - + +1.6) Latest release of PostgreSQL + +The latest release of PostgreSQL is version 6.2.1, which was released on +October 17th, 1997. We are testing 6.3 beta. For information about what is +new in 6.3, see our TODO list on our WWW page. + +We plan to have major releases every three months. + +1.7) Is there a commercial version of PostgreSQL? + +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 +PostgreSQL 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 PostgreSQL? + +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 PostgreSQL use? + +PostgreSQL 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 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 PostgreSQL coding, +eventually we can also add the missing features listed above. + +1.10) Does PostgreSQL work with databases from earlier versions of postgres? + +PostgreSQL v1.09 is compatible with databases created with v1.01. + +Upgrading to 6.3 from earlier releases requires a dump and restore. + +Upgrading to 6.2.1 from pre-6.2 requires a dump and restore. + +Upgrading to 6.2.1 from 6.2 does not require a dump, but see the appropriate +/migration file in the distribution. + +Those ugrading from versions earlier than 1.09 must upgrade to 1.09 first +without a dump/reload, then dump the data from 1.09, and then load it into +6.2.1 or 6.3 beta. + +1.11) Are there ODBC drivers for PostgreSQL? + +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 very popular. You can get it from +http://www.openlinksw.com/postgres.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. + +1.12) What tools are available for hooking postgres to Web pages? + +A nice introduction to Database-backed Web pages can be seen at: +http://www.webtools.com + +For web integration, PHP is an excellent interface. The URL for that is +http://php.iquest.net + +PHP is great for simple stuff, but for more complex stuff, some still use +the perl interface and CGI.pm. + +An WWW gatway based on WDB using perl can be downloaded from: + + * http://www.eol.ists.ca/~dunlop/wdb -p95 + +1.13) Does PostgreSQL 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 +PostgreSQL. Several contributions are working on tk based frontend tools. +Ask on the mailing list. + +1.14) What is a good book to learn SQL? + +Many of our users like The Practical SQL Handbook, Bowman et al, Addison +Wesley. + + ------------------------------------------------------------------------ + Section 2: Installation Questions - 2.1) 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 - - 2.2) 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. - - 2.3) The system seems to be confused about commas, decimal points, and date - formats. - - Check your locale configuration. PostgreSQL uses the locale settings - of the user that ran the postmaster process. Set those accordingly for - your operating environment. - - 2.4) How do I install PostgreSQL somewhere other than /usr/local/pgsql? - - You need to edit Makefile.global and change POSTGRESDIR accordingly, - or create a Makefile.custom and define POSTGRESDIR there. - - 2.5) 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. PostgreSQL requires - kernel support for shared memory. - - 2.6) 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. - - 2.7) I have changed a source file, but a recompile does not see the change? - - The Makefiles do not have the proper dependencies for include files. - You have to do a 'make clean' and then another 'make'. - - 2.8) How do I prevent other hosts from accessing my PostgreSQL backend? - - Use host-based authentication by modifying the file $PGDATA/pg_hba - accordingly. - - 2.9) 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. - - 2.10) All my servers crash under concurrent table access. Why? - - This problem can be caused by a kernel that is not configured to - support semaphores. - - 2.11) How do I tune the database engine for better performance? - - 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. - - 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 can also use the postgres -S option to increase the maximum amount - of memory used by each backend process for temporary sorts. Each - buffer is 1K and the defualt is 512 buffers. - - 2.12) What debugging features are available in PostgreSQL? - - PostgreSQL has several features that report status information that - can be valuable for debugging purposes. - - First, by running configure with the -enable-cassert option, many - assert()'s monitor the progress of the backend and halt the program - when something unexpected occurs. - - 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: +2.1) 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 + +2.2) 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. +2.3) The system seems to be confused about commas, decimal points, and date +formats. + +Check your locale configuration. PostgreSQL uses the locale settings of the +user that ran the postmaster process. Set those accordingly for your +operating environment. + +2.4) How do I install PostgreSQL somewhere other than /usr/local/pgsql? + +You need to edit Makefile.global and change POSTGRESDIR accordingly, or +create a Makefile.custom and define POSTGRESDIR there. + +2.5) 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. PostgreSQL requires kernel +support for shared memory. + +2.6) 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. + +2.7) I have changed a source file, but a recompile does not see the change? + +The Makefiles do not have the proper dependencies for include files. You +have to do a 'make clean' and then another 'make'. + +2.8) How do I prevent other hosts from accessing my PostgreSQL backend? + +Use host-based authentication by modifying the file $PGDATA/pg_hba +accordingly. + +2.9) 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. + +2.10) All my servers crash under concurrent table access. Why? + +This problem can be caused by a kernel that is not configured to support +semaphores. + +2.11) How do I tune the database engine for better performance? + +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. + +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 can also use the postgres -S option to increase the maximum amount of +memory used by each backend process for temporary sorts. Each buffer is 1K +and the defualt is 512 buffers. + +2.12) What debugging features are available in PostgreSQL? + +PostgreSQL has several features that report status information that can be +valuable for debugging purposes. + +First, by running configure with the -enable-cassert option, many assert()'s +monitor the progress of the backend and halt the program when something +unexpected occurs. + +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: cd /usr/local/pgsql ./bin/postmaster >server.log 2>&1 & - This will put a server.log file in the top-level PostgreSQL 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. Be warned that a debug level of 3 - generates large log files. - - 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 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. - - The postgres program has a -s, -A, -t options that can be very usefull - for debugging and performance measurements. - - You can also compile with profiling to see what functions are taking - execution time. The backend profile files will be deposited in the - pgsql/data/base/dbname directory. The client profile file will be put - in the current directory. - - The EXPLAIN command (see this FAQ) allows you to see how PostgreSQL is - interpreting your query. - - 2.13) How do I enable more than 32 concurrent backends? - - Edit include/storage/sinvaladt.h, and change the value of - MaxBackendId. In the future, we plan to make this a configurable - prameter. - _________________________________________________________________ - +This will put a server.log file in the top-level PostgreSQL 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. Be warned that a debug level of 3 generates large log +files. + +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 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. + +The postgres program has a -s, -A, -t options that can be very usefull for +debugging and performance measurements. + +You can also compile with profiling to see what functions are taking +execution time. The backend profile files will be deposited in the +pgsql/data/base/dbname directory. The client profile file will be put in the +current directory. + +The EXPLAIN command (see this FAQ) allows you to see how PostgreSQL is +interpreting your query. + +2.13) How do I enable more than 32 concurrent backends? + +Edit include/storage/sinvaladt.h, and change the value of MaxBackendId. In +the future, we plan to make this a configurable prameter. + + ------------------------------------------------------------------------ + Section 3: PostgreSQL Features - 3.1) Does PostgreSQL support nested subqueries? - - Subqueries are not implemented, but they can be simulated using sql - functions. - - 3.2) I've having a lot of problems using rules. - - Currently, the rule system in PostgreSQL is mostly broken. It works - enough to support the view mechanism, but that's about it. Use - PostgreSQL rules at your own peril. - - 3.3) I can't seem to write into the middle of large objects reliably. - - The Inversion large object system in PostgreSQL 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 - PostgreSQL large objects at your own peril. - - 3.4) How can I write client applications to PostgreSQL? - - PostgreSQL supports a C-callable library interface called libpq as - well as many others. See the /src/interfaces directory. - - Others have contributed a perl interface and a WWW gateway to - PostgreSQL. See the PostgreSQL home pages for more details. - - 3.5) 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: +3.1) Does PostgreSQL support nested subqueries? + +Subqueries are not implemented, but they can be simulated using sql +functions. + +3.2) I've having a lot of problems using rules. + +Currently, the rule system in PostgreSQL is mostly broken. It works enough +to support the view mechanism, but that's about it. Use PostgreSQL rules at +your own peril. + +3.3) I can't seem to write into the middle of large objects reliably. + +The Inversion large object system in PostgreSQL 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 PostgreSQL large +objects at your own peril. + +3.4) How can I write client applications to PostgreSQL? +PostgreSQL supports a C-callable library interface called libpq as well as +many others. See the /src/interfaces directory. + +Others have contributed a perl interface and a WWW gateway to PostgreSQL. +See the PostgreSQL home pages for more details. + +3.5) 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}'); @@ -516,84 +506,82 @@ Section 3: PostgreSQL Features 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[]. - - 3.6) What is the exact difference between binary cursors and normal cursors? - - See the declare manual page for a description. - - 3.7) 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" - - 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. - - 3.8) 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. - - 3.9) I defined indices but my queries don't seem to make use of them. Why? - - PostgreSQL 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). For column-specific optimization - statistics, use 'vacuum analyze'. - - 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. - - 3.10) How do I do regular expression searches? case-insensitive regexp - searching? - - See the pgbuiltin manual page. Search for regular expression. - - 3.11) I experienced a server crash during a vacuum. How do I remove the lock - file? - - See the vacuum manual page. - - 3.12) What is the difference between the various character types? - +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[]. + +3.6) What is the exact difference between binary cursors and normal cursors? + +See the declare manual page for a description. + +3.7) 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" + +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. + +3.8) 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. + +3.9) I defined indices but my queries don't seem to make use of them. Why? + +PostgreSQL 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). For column-specific optimization statistics, use 'vacuum +analyze'. + +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. + +3.10) How do I do regular expression searches? case-insensitive regexp +searching? + +See the pgbuiltin manual page. Search for regular expression. + +3.11) I experienced a server crash during a vacuum. How do I remove the lock +file? + +See the vacuum manual page. + +3.12) What is the difference between the various character types? + Type Internal Name Notes -------------------------------------------------- CHAR char 1 character } @@ -606,34 +594,34 @@ 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 are the length, followed by the data). CHAR(#) allocates the - maximum number of bytes no matter how much data is stored in the - field. TEXT, VARCHAR(#), and BYTEA all have variable length on the - disk. - - 3.13) In a query, how do I detect if a field is NULL? - - You test the column with IS NULL and IS NOT NULL. - - 3.14) How do I see how the query optimizer is evaluating my query? - - See the explain manual page. - - 3.15) 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 use - pgdump's -o option or COPY's WITH OIDS option to preserver the oids. - - We also have a SEQUENCE function that is similar to SERIAL. See the - create_sequence manual page. - - Another valid way of doing this is to create a function: +You need to use the internal name when doing internal operations. + +The last four types above are "varlena" types (i.e. the first four bytes are +the length, followed by the data). CHAR(#) allocates the maximum number of +bytes no matter how much data is stored in the field. TEXT, VARCHAR(#), and +BYTEA all have variable length on the disk, and because of this, there is a +small performance penalty for using them. Specifically, the penalty is for +access to any columns after the first column of this type. + +3.13) In a query, how do I detect if a field is NULL? + +You test the column with IS NULL and IS NOT NULL. + +3.14) How do I see how the query optimizer is evaluating my query? + +See the explain manual page. + +3.15) 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 use pgdump's -o option or +COPY's WITH OIDS option to preserver the oids. + +We also have a SEQUENCE function that is similar to SERIAL. See the +create_sequence manual page. + +Another valid way of doing this is to create a function: create table my_oids (f1 int4); insert into my_oids values (1); @@ -641,118 +629,115 @@ BYTEA bytea variable-length array of bytes 'update my_oids set f1 = f1 + 1; select f1 from my_oids; ' language 'sql'; - then: +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. - - Yet another way is to use general trigger function autoinc() from - contrib/spi/autoinc.c. - - 3.16) What are the pg_psort.XXX files in my database directory? - - They are temporary sort 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 pg_psort.XXX files. - - 3.17) 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 pgsql/data/pg_hba. - See the hba_conf manual page. - - 3.18) How do I find out what indexes or operations are defined in the - database? - - Run the file pgsql/src/tutorial/syscat.source. It illustrates many of - the 'select's needed to get information out of the database system - tables. - - 3.19) What is the time-warp feature and how does it relate to vacuum? - - PostgreSQL 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. +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. +Yet another way is to use general trigger function autoinc() from +contrib/spi/autoinc.c. + +3.16) What are the pg_psort.XXX files in my database directory? + +They are temporary sort 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 pg_psort.XXX files. + +3.17) 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 pgsql/data/pg_hba. See +the hba_conf manual page. + +3.18) How do I find out what indexes or operations are defined in the +database? + +Run the file pgsql/src/tutorial/syscat.source. It illustrates many of the +'select's needed to get information out of the database system tables. + +3.19) What is the time-warp feature and how does it relate to vacuum? + +PostgreSQL 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'] - 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. - - INSERTed rows get a timestamp too, so rows that were not in the table - at the desired time will not appear. - - Vacuum removes rows that are no longer current. This time-warp feature - is used by the engine for rollback and crash recovery. Expiration - times can be set with purge. - - In 6.0, once a table is vacuumed, the creation time of a row may be - incorrect, causing time-traval to fail. - - The time-travel feature will be removed in 6.3. - - 3.20) What is an oid? What is a tid? - - 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. - - 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. You can create an index on the oid field for faster access. - - 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. - - 3.21) What is the meaning of some of the terms used in Postgres? - - Some of the source code and older documentation use terms that have - more common usage. Here are some: - * row, record, tuple - * attribute, field, column - * table, class - * retrieve, select - * replace, update - * append, insert - * oid, serial value - * portal, cursor - * range variable, table name, table alias - - Please let me know if you think of any more. - - 3.22) What is Genetic Query Optimization? - - The GEQO module in PostgreSQL is intended to solve the query - optimization problem of joining many tables by means of a Genetic - Algorithm (GA). It allows the handling of large join queries through - non-exhaustive search. - - For further information see README.GEQO . - - 3.23) How do you remove a column from a table? - - We do not support ALTER TABLE DROP COLUMN, but do this: +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. + +INSERTed rows get a timestamp too, so rows that were not in the table at the +desired time will not appear. + +Vacuum removes rows that are no longer current. This time-warp feature is +used by the engine for rollback and crash recovery. Expiration times can be +set with purge. + +In 6.0, once a table is vacuumed, the creation time of a row may be +incorrect, causing time-traval to fail. + +The time-travel feature will be removed in 6.3. + +3.20) What is an oid? What is a tid? + +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. + +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. You can create an +index on the oid field for faster access. + +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. + +3.21) What is the meaning of some of the terms used in Postgres? + +Some of the source code and older documentation use terms that have more +common usage. Here are some: + + * row, record, tuple + * attribute, field, column + * table, class + * retrieve, select + * replace, update + * append, insert + * oid, serial value + * portal, cursor + * range variable, table name, table alias + +Please let me know if you think of any more. + +3.22) What is Genetic Query Optimization? + +The GEQO module in PostgreSQL is intended to solve the query optimization +problem of joining many tables by means of a Genetic Algorithm (GA). It +allows the handling of large join queries through non-exhaustive search. + +For further information see README.GEQO . + +3.23) How do you remove a column from a table? + +We do not support ALTER TABLE DROP COLUMN, but do this: SELECT ... -- select all columns but the one you want to remove INTO TABLE new_table @@ -760,28 +745,27 @@ BYTEA bytea variable-length array of bytes DROP TABLE old_table; ALTER TABLE new_table RENAME TO old_table; - 3.24) How do SELECT only the first few rows of a query? - - See the fetch manual page. - - This only prevents all row results from being transfered to the - client. The entire query must be evaluated, even if you only want just - first few rows. Consider a query that has and ORDER BY. There is no - way to return any rows until the entire query is evaluated and sorted. - - 3.25) Why can't I create a column named "time"? - - 6.2.1 has added some new restricted keywords as we make PostgreSQL - more ANSI-92 compilant. The next release will have this restriction - removed. There is a patch on ftp.postgresql.org that will allow this - feature now. - - 3.26)How much database disk space is required to store data from a typical - flat file? - - Consider a file with 300,000 lines with two integers on each line. The - flat file is 2.4MB. The size of the PostgreSQL database file - containing this data can be estimated: +3.24) How do SELECT only the first few rows of a query? + +See the fetch manual page. + +This only prevents all row results from being transfered to the client. The +entire query must be evaluated, even if you only want just first few rows. +Consider a query that has and ORDER BY. There is no way to return any rows +until the entire query is evaluated and sorted. + +3.25) Why can't I create a column named "time"? + +6.2.1 has added some new restricted keywords as we make PostgreSQL more +ANSI-92 compilant. The next release will have this restriction removed. +There is a patch on ftp.postgresql.org that will allow this feature now. + +3.26)How much database disk space is required to store data from a typical +flat file? + +Consider a file with 300,000 lines with two integers on each line. The flat +file is 2.4MB. The size of the PostgreSQL database file containing this data +can be estimated: 40 bytes + each row header (approximate) 8 bytes + two int fields @ 4 bytes each @@ -803,49 +787,51 @@ The data page size in PostgreSQL is 8192(8k) bytes, so: Indexes do not contain as much overhead, but do contain the data that is being indexed, so they can be large also. - _________________________________________________________________ - + + ------------------------------------------------------------------------ + Section 4: Extending PostgreSQL - 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 - - 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. - - 4.3) I've written some nifty new types and functions for PostgreSQL. - - Please share them with other PostgreSQL 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? - - 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. - _________________________________________________________________ - +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 + +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. + +4.3) I've written some nifty new types and functions for PostgreSQL. + +Please share them with other PostgreSQL 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? + +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 make a bug report? - - Check the current FAQ at http://postgreSQL.org - - Also check out our ftp site ftp://ftp.postgreSQL.org/pub to see if - there is a more recent PostgreSQL version. - - You can also fill out the "bug-template" file and send it to: - * bugs@postgreSQL.org - - This is the address of the developers mailing list. +5.1) How do I make a bug report? + +Check the current FAQ at http://postgreSQL.org + +Also check out our ftp site ftp://ftp.postgreSQL.org/pub to see if there is +a more recent PostgreSQL version. + +You can also fill out the "bug-template" file and send it to: + + * bugs@postgreSQL.org + +This is the address of the developers mailing list. diff --git a/doc/FAQ_Linux b/doc/FAQ_Linux index 313187ddea..e420e26944 100644 --- a/doc/FAQ_Linux +++ b/doc/FAQ_Linux @@ -4,7 +4,7 @@ Frequently Asked Questions (FAQ) for PostgreSQL >= V6.1 Linux Specific TO BE READ IN CONJUNCTION WITH THE NORMAL FAQ ======================================================= -last updated: Thu Dec 15 12:05:00 GMT 1997 +last updated: Wed Feb 18 13:00:00 GMT 1997 current maintainer: Andrew C.R. Martin (martin@biochem.ucl.ac.uk) original author: Andrew C.R. Martin (martin@biochem.ucl.ac.uk) @@ -12,10 +12,8 @@ original author: Andrew C.R. Martin (martin@biochem.ucl.ac.uk) Changes in this version (* = modified, + = new, - = removed): -*1.3) [REDHAT] Why do I get problems with missing libdl and dlfcn.h? -*1.4) [SLACKWARE 3.1] Why do I get problems with missing libdl and dlfcn.h? -+1.19) Why does make exit or crash? - ++1.20) How can I optimise for 486 or pentium processors ++3.10) Why do I get funny rounding results in some date/time arithmetic... This file is divided approximately as follows: 1.*) Installing PostgreSQL @@ -55,6 +53,7 @@ Questions answered: 1.17) When compiling postgres, gcc reports signal 11 and aborts. 1.18) Can I install 6.1.1 under MkLinux? 1.19) Why does make exit or crash? +1.20) How can I optimise for 486 or pentium processors 2.1) The linker fails to find libX11 when compiling pgtclsh 3.1) I get an error reporting _fUnKy_POSTPORT_sTuFf_ undefined when running scripts like createuser @@ -77,6 +76,10 @@ Questions answered: 3.8) When PostgreSQL is running when the system is shutdown, Linux always fsck's the disk when rebooted. 3.9) Why does Query 32 in the regression tests take so long? +3.10) Why do I get funny rounding results in some date/time arithmetic, + such as + select '4 hours'::timespan; + returning '3 hours 59 minutes 60 seconds'? ---------------------------------------------------------------------- Section 1: Compiling PostgreSQL @@ -298,7 +301,7 @@ Section 1: Compiling PostgreSQL Some versions of SuSE provide only ncurses, so you may need to force use of ncurses rather than curses by changing - -lcurses to -lncurses. + -lcurses to -lncurses. (Reported true for SuSE 5.1) 1.9) Why do I get problems with ld.so? @@ -430,6 +433,19 @@ Section 1: Compiling PostgreSQL In short, try upgrading gmake to the latest version you can find before reporting this as a problem +1.20) How can I optimise for 486 or pentium processors + + The default compiler flags perform no optimisation for 486 + or Pentium processors. To add such optimisation, edit + Makefile.custom and add: + + CFLAGS+= -m486 + + or (for the new compilers that most people are not yet running) + + CFLAGS+= -mpentium + or + CFLAGS+= -mpentiumpro ---------------------------------------------------------------------- Section 2: Compiling accessory programs @@ -617,6 +633,15 @@ exit 0 then type: sh ./perquery < bench.out > & bench.out.perquery + + +3.10) Why do I get funny rounding results in some date/time arithmetic, + such as + select '4 hours'::timespan; + returning '3 hours 59 minutes 60 seconds'? + + You are running the new glibc2 libraries and have a version earlier than + 2.0.7. It is a math rounding problem in the library. Upgrade your library. ---------------------------------------------------------------------------- Dr. Andrew C.R. Martin University College London EMAIL: (Work) martin@biochem.ucl.ac.uk (Home) andrew@stagleys.demon.co.uk diff --git a/src/tools/FAQ_DEV b/src/tools/FAQ_DEV new file mode 100644 index 0000000000..f44d922b4b --- /dev/null +++ b/src/tools/FAQ_DEV @@ -0,0 +1,140 @@ +Developer's Frequently Asked Questions (FAQ) for PostgreSQL + +Last updated: Wed Feb 11 20:23:01 EST 1998 + +Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us) + +The most recent version of this document can be viewed at the postgreSQL Web +site, http://postgreSQL.org. + + ------------------------------------------------------------------------ + +Questions answered: + +1) What tools are available for developers? +2) What books are good for developers? +3) Why do we use palloc() and pfree() to allocate memory? +4) Why do we use Node and List to make data structures? +5) How do I add a feature or fix a bug? +6) How do I download/update the current source tree? +7) How do I test my changes? + + ------------------------------------------------------------------------ + +1) What tools are available for developers? + +Aside from the User documentation mentioned in the regular FAQ, there are +several development tools available. First, all the files in the /tools +directory are designed for developers. + + RELEASE_CHANGES changes we have to make for each release + SQL_keywords standard SQL'92 keywords + backend web flowchart of the backend directories + ccsym find standard defines made by your compiler + entab converts tabs to spaces, used by pgindent + find_static finds functions that could be made static + find_typedef get a list of typedefs in the source code + make_ctags make vi 'tags' file in each directory + make_diff make *.orig and diffs of source + make_etags make emacs 'etags' files + make_keywords.README make comparison of our keywords and SQL'92 + make_mkid make mkid ID files + mkldexport create AIX exports file + pgindent indents C source files + +Let me note some of these. If you point your browser at the tools/backend +directory, you will see all the backend components in a flow chart. You can +click on any one to see a description. If you then click on the directory +name, you will be taken to the source directory, to browse the actual source +code behind it. We also have several README files in some source directories +to describe the function of the module. The browser will display these when +you enter the directory also. The tools/backend directory is also contained +on our web page under the title Backend Flowchart. + +Second, you really should have an editor that can handle tags, so you can +tag a function call to see the function definition, and then tag inside that +function to see an even lower-level function, and then back out twice to +return to the original function. Most editors support this via tags or etags +files. + +Third, you need to get mkid from ftp.postgresql.org. By running +tools/make_mkid, an archive of source symbols can be created that can be +rapidly queried like grep or edited. + +make_diff has tools to create patch diff files that can be applied to the +distribution. + +pgindent will format source files to match our standard format, which has +four-space tabs, and an indenting format specified by flags to the your +operating system's utility indent. + +2) What books are good for developers? + +I have two good books, An Introduction to Database Systems, by C.J. Date, +Addison, Wesley and A Guide to the SQL Standard, by C.J. Date, et. al, +Addison, Wesley. + +3) Why do we use palloc() and pfree() to allocate memory? + +palloc() and pfree() are used in place of malloc() and free() because we +automatically free all memory allocated when a transaction completes. This +makes it easier to make sure we free memory that gets allocated in one +place, but only freed much later. There are several contexts that memory can +be allocated in, and this controls when the allocated memory is +automatically freed by the backend. + +4) Why do we use Node and List to make data structures? + +We do this because this allows a consistent way to pass data inside the +backend in a flexible way. Every node has a NodeTag which specifies what +type of data is inside the Node. Lists are lists of Nodes. lfirst(), +lnext(), and foreach() are used to get, skip, and traverse through Lists. + +5) How do I add a feature or fix a bug? + +The source code is over 250,000 lines. Many problems/features are isolated +to one specific area of the code. Others require knowledge of much of the +source. If you are confused about where to start, ask the hackers list, and +they will be glad to assess the complexity and give pointers on where to +start. + +Another thing to keep in mind is that many fixes and features can be added +with surprisingly little code. I often start by adding code, then looking at +other areas in the code where similar things are done, and by the time I am +finished, the patch is quite small and compact. + +When adding code, keep in mind that it should use the existing facilities in +the source, for performance reasons and for simplicity. Often a review of +existing code doing similar things is helpful. + +6) How do I download/update the current source tree? + +There are several ways to obtain the source tree. Occasional developers can +just get the most recent source tree snapshot from ftp.postgresql.org. For +regular developers, you can get CVSup, which is available from +ftp.postgresql.org too. CVSup allows you to download the source tree, then +occasionally update your copy of the source tree with any new changes. Using +CVSup, you don't have to download the entire source each time, only the +changed files. CVSup does not allow developers to update the source tree. + +To update the source tree, there are two ways. You can generate a patch +against your current source tree, perhaps using the make_diff tools +mentioned above, and send them to the patches list. They will be reviewed, +and applied in a timely manner. If the patch is major, and we are in beta +testing, the developers may wait for the final release before applying your +patches. + +For hard-core developers, Marc(scrappy@postgresql.org) will give you a Unix +shell account on postgresql.org, and you can ftp your files into your +account, patch, and cvs install the changes directly into the source tree. + +6) How do I test my changes? + +First, use psql to make sure it is working as you expect. Then run +src/test/regress and get the output of src/test/regress/checkresults with +and without your changes, to see that your patch does not change the +regression test in unexpected ways. This practice has saved me many times. +The regression tests test the code in ways I would never do, and has caught +many bugs in my patches. By finding the problems now, you save yourself a +lot of debugging later when things are broken, and you can't figure out when +it happened.