-Last updated: Wed Jun 11 10:44:40 EDT 1997
-
-Version: 6.1
-
-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.phtml. -
-Irix-specific questions are answered in -http://postgreSQL.org/docs/FAQ-Irix.phtml. -
-Changes in this version (* = modified, + = new): -
-
-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. -
-
-The authors have compiled and tested PostgreSQL on the following -platforms(some of these compiles require gcc 2.7.0): -
-
The primary anonymous ftp site for PostgreSQL is: -
-A mirror site exists at: -
-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. -
-
-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: -
- - 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: -
-
- - subscribe - end - --
-Additional information about PostgreSQL can be found via the PostgreSQL -WWW home page at: -
- http://postgreSQL.org --
-
-The latest release of PostgreSQL is version 6.0, which was released on -January 31, 1997. 6.1 is scheduled for release soon. For information -about what is new in 6.1, see our TODO list on our WWW page. -
-We expect a 7.0 release in several months that will remove time-travel -and reduce by 50% the size of on-disk system columns maintained for each -row in a table. This release will also require a dump and restore. -
-
-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 -
-
-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. -
-
-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: -
-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. -
-
-PostgreSQL v1.09 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. -
-Upgrading to 6.0 requires a dump and restore from previous releases. -
-Upgrading to 6.1 requires a dump and restore from previous releases. -
-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 6.0 or 6.1. -
-
-Since we don't have any licensing or registration scheme, it's -impossible to tell. We do know hundreds copies of PostgreSQL v1.* have -been downloaded, and that there many hundreds of subscribers to the -mailing lists. -
-
-
-
-
-You probably do not have the right path set up. The 'postgres' -executable needs to be in your path. -
-
-Check your locale configuration. PostgreSQL uses the locale settings of -the user that ran the postmaster process. Set those accordingly for -your operating environment. -
-
-You need to edit Makefile.global and change POSTGRESDIR accordingly, or -create a Makefile.custom and define POSTGRESDIR there. -
-
-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. -
-
-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. -
-
-The Makefiles do not have the proper dependencies for include files. You -have to do a 'make clean' and then another 'make'. -
-
-
-Column constraints are not supported in PostgreSQL. As a consequence, -the system does not check for duplicates. -
-Under 6.0, create a unique index on the column. Attempts to create -duplicate of that column will report an error. -
-
-Subqueries are not implemented, but they can be simulated using sql -functions. -
-
-PostgreSQL 6.0 supports unique indices. -
-
-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. -
-
-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. -
-
-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. -
-
-PostgreSQL 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 -PostgreSQL. See the PostgreSQL home pages for more details. -
-
-Use host-based authentication by modifying the file $PGDATA/pg_hba -accordingly. -
-
-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: -
-
-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. -
-
-SQL specifies <> as the inequality operator, and that is what we -have defined for the built-in types. -
-In 6.0, != is equivalent to <>. -
-
-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" -
-
-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. -
-
-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). -
-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. -
-
-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: -
--these lists are ordinary majordomo mailing lists. You can subscribe by -sending a mail to: -
--OpenLink ODBC is currently in beta under Linux. 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. -
-
-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. -
-
-PostgreSQL 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. -
-
-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. -
-
-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>) -
-
+ 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 OSF/1 2.0
+ * 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 5.4R3.10
+ * hpux - HP PA-RISC on HP-UX 9.0
+ * i386_solaris - i386 Solaris
+ * irix5 - SGI MIPS on IRIX 5.3
+ * linux - Intel x86 on Linux 1.2 and Linux ELF (For non-ELF Linux,
+ see LINUX_ELF below).
+ * sparc_solaris - SUN SPARC on Solaris 2.4
+ * sunos4 - SUN SPARC on SunOS 4.1.3
+ * svr4 - Intel x86 on Intel SVR4
+ * 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:
+
+
+ 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:
+
+
+ subscribe
+ end
+
+ 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 6.1.1, which will be
+ released in July, 1997. For information about what is new in 6.1.1,
+ see our TODO list on our WWW page.
+
+ We expect a 7.0 release in several months that will remove time-travel
+ and reduce by 50% the size of on-disk system columns maintained for
+ each row in a table. This release will also require a dump and
+ restore.
+
+ 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.
+ Those upgrading from 1.0 should read the directions in the
+ MIGRATION_1.0_TO_1.02 directory.
+
+ Upgrading to 6.0 requires a dump and restore from previous releases.
+
+ Upgrading to 6.1 requires a dump and restore from previous releases.
+
+ Upgrading from 6.1 to 6.1.1 requires a compile of the new release,
+ recompile of all your custom applications to use the new libpq, and
+ then an install while the postmaster is temporarily stopped.
+
+ 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 6.1.1.
+
+ 1.11) How many people use PostgreSQL?
+
+ Since we don't have any licensing or registration scheme, it's
+ impossible to tell. We do know hundreds copies of PostgreSQL v1.* have
+ been downloaded, and that there many hundreds of subscribers to the
+ mailing lists.
+
+ _________________________________________________________________
+
+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'.
+
+ _________________________________________________________________
+
+Section 3: PostgreSQL Features
+
+ 3.1) How do I specify a KEY or other constraints on a column?
+
+ Column constraints are not supported in PostgreSQL. As a consequence,
+ the system does not check for duplicates.
+
+ Under 6.0, create a unique index on the column. Attempts to create
+ duplicate of that column will report an error.
+
+ 3.2) Does PostgreSQL support nested subqueries?
+
+ Subqueries are not implemented, but they can be simulated using sql
+ functions.
+
+ 3.3) How do I define a unique indices?
+
+ PostgreSQL 6.0 supports unique indices.
+
+ 3.4) 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.
+
+ 3.5) 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.
+
+ 3.6) 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.
+
+ 3.7) How can I write client applications to PostgreSQL?
+
+ PostgreSQL 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
+ PostgreSQL. See the PostgreSQL home pages for more details.
+
+ 3.8) How do I prevent other hosts from accessing my PostgreSQL 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.
+
+ In 6.0, != is equivalent to <>.
+
+ 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?
+
+ 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).
+
+ 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 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 currently in beta under Linux. 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.
+
+ 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?
+
+ PostgreSQL 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 }
@@ -676,368 +591,322 @@ 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. -
-
-PostgreSQL has two builtin keywords, "isnull" and "notnull" (note no -spaces). Version 1.05 and later and 6.* understand IS NULL and IS NOT -NULL. -
-
-Place the word 'EXPLAIN' at the beginning of the query, for example: -
-
- EXPLAIN SELECT * FROM table1 WHERE age = 23;
-
-
--
-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 later or 6.* 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. -
-Sequences are implemented in 6.1 -
-
-In 6.0, 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. -
-In 6.1, this feature is available. -
-
-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. -
-
-If you run vacuum in pre-6.0, unused rows will be marked for reuse, but -the file blocks are not released. -
-In 6.0, vacuum properly shrinks tables. -
-
-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. -
-
-You probably used: -
-
- create index idx1 on person using btree (name);
-
-
--PostgreSQL indexes are extensible, and therefore in pre-6.0, you must -specify a class_type when creating an index. Read the manual page for -create index (called create_index). -
-Version 6.0, if you do not specify a class_type, it defaults to the -proper type for the column. -
-
-You have probably defined an incorrect *_ops type class for the field -you are indexing. -
-
-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. -
-
-You have compile postgres with flex version 2.5.3. There is bug in this -version of flex. Use flex version 2.5.2 or flex 2.5.4 instead. There -is a doc/README.flex file which will properly patch the flex 2.5.3 -source code. -
-
-This problem can be caused by a kernel that is not configured to support -semaphores. -
-
-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: -
--An WWW gatway based on WDB using perl can be downloaded from: -
--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 7.0. -
-
-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. -
-
-PostgreSQL has several features that report status information that can -be valuable for debugging purposes. -
-First, by compiling with DEBUG defined, 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. The query plans in a verbose debug -file can be formatted using the 'indent' program. (You may need to -remove the '====' lines in 1.* releases.) Be warned that a debug level -greater than one generates large log files in 1.* releases. -
-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. -
-The postgres program has a -s, -A, -t options that can be very usefull -for debugging and performance measurements. -
-The EXPLAIN command (see this FAQ) allows you to see how PostgreSQL is -iterpreting your query. -
-
-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. -
-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. -
-
-Some of the source code and older documentation use terms that have more -common usage. Here are some: -
-Please let me know if you think of any more. -
-
-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 <utesch@aut.tu-freiberg.de>. -
-
-There was a bug in 6.0 that caused this problem under Solaris with -O2 -optimization. -Upgrade to 6.1. -
-
-Edit include/storage/sinvaladt.h, and change the value of MaxBackendId. -In the future, we plan to make this a configurable prameter. -
-
-
-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 -
-
-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. -
-
-Please share them with other PostgreSQL users. Send your extensions to -mailing list, and they will eventually end up in the contrib/ -subdirectory. -
-
-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. -
-
-
-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: -
-
-This is the address of the developers mailing list.
-
-
+ 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?
+
+ PostgreSQL has two builtin keywords, "isnull" and "notnull" (note no
+ spaces). Version 1.05 and later and 6.* 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 later or 6.* 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.
+
+ Sequences were implemented in 6.1
+
+ 3.24) How do I create a multi-column index?
+
+ In 6.0, 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.
+
+ In 6.1, this feature is available.
+
+ 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 in pre-6.0, unused rows will be marked for reuse,
+ but the file blocks are not released.
+
+ In 6.0, vacuum properly shrinks tables.
+
+ 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 pgsql/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);
+
+ PostgreSQL indexes are extensible, and therefore in pre-6.0, you must
+ specify a class_type when creating an index. Read the manual page for
+ create index (called create_index).
+
+ Version 6.0, if you do not specify a class_type, it defaults to the
+ proper type for the column.
+
+ 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 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.
+
+ 3.31) Why do statements require an extra character at the end? Why does
+ 'createuser' return 'unexpected last match in input()'? Why does pg_dump
+ fail?
+
+ You have compile postgres with flex version 2.5.3. There is bug in
+ this version of flex. Use flex version 2.5.2 or flex 2.5.4 instead.
+ There is a doc/README.flex file which will properly patch the flex
+ 2.5.3 source code.
+
+ 3.32) All my servers crash under concurrent table access. Why?
+
+ This problem can be caused by a kernel that is not configured to
+ support semaphores.
+
+ 3.33) 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://postgreSQL.org/~mlc
+
+ An WWW gatway based on WDB using perl can be downloaded from:
+ * http://www.eol.ists.ca/~dunlop/wdb -p95
+
+ 3.34) 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 7.0.
+
+ 3.35) 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.
+
+ 3.36) What debugging features are available in PostgreSQL?
+
+ PostgreSQL has several features that report status information that
+ can be valuable for debugging purposes.
+
+ First, by compiling with DEBUG defined, 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. The query plans in a verbose debug
+ file can be formatted using the 'indent' program. (You may need to
+ remove the '====' lines in 1.* releases.) Be warned that a debug level
+ greater than one generates large log files in 1.* releases.
+
+ 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.
+
+ The postgres program has a -s, -A, -t options that can be very usefull
+ for debugging and performance measurements.
+
+ The EXPLAIN command (see this FAQ) allows you to see how PostgreSQL is
+ iterpreting your query.
+
+ 3.37) 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.
+
+ 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.
+
+ 3.38) 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.
+
+ 3.39) 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