=================================================
Frequently Asked Questions (FAQ) for Postgres95
==================================================
last updated:	Mon Feb 26 10:56:29 PST 1996
author:		Jolly Chen (jolly@cs.berkeley.edu)
availability:	This file is available via anonymous ftp as
			s2k-ftp.cs.berkeley.edu/pub/postgres95/FAQ
		More information is available via the Postgres95 WWW pages:
			http://s2k-ftp.cs.berkeley.edu:8000/postgres95

changes in this version (* = modified, + = new):
* 1.3) Where can I get Postgres95
* 1.5) Support for Postgres95
* 1.6) Future releases of Postgres95
* 1.8) What documentation is available for Postgres95?
* 1.10) Does Postgres95 work with databases from earlier versions of postgres?
+ 2.10)	When I run postmaster, I get a Bad System Call core dumped message.
+ 2.11) I get the error message "obj/fmgr.h: No such file or directory"
* 3.6) Does postgres95 have a graphical user interface?
* 3.8) How do I prevent other hosts from accessing my Postgres95 backend?
+ 3.17)	How do I use postgres for multi-dimensional indexing (> 2 dimensions)?
+ 3.18) How do I do regular expression searches?  case-insensitive regexp?

This file is divided approximately as follows:
	1.*)	General questions
	2.*)	Installation questions
	3.*)	Postgres95 Features questions
	4.*)	Questions about extending Postgres95
	5.*)	Bugs

----------------------------------------------------------------------
Section 1:	General Questions
----------------------------------------------------------------------

1.1)	What is Postgres95?

	Postgres95 is an enhancement of the POSTGRES database
	management system, a next-generation DBMS research prototype. 
	While Postgres95 retains the powerful data model and rich data
	types of POSTGRES, it replaces the PostQuel query language with an
	extended subset of SQL.  Postgres95 is free and the complete
	source is available. 

	The primary authors of Postgres95 are Andrew Yu and Jolly Chen.
	Many others have contributed to the porting, testing, debugging and
	enhancement of the code.  The original Postgres code, from which
	Postgres95 is derived, was the effort of many graduate
	students, undergraduate students, and staff programmers
	working under the direction of Professor Michael Stonebraker
	at the University of California, Berkeley. 

1.2) 	What does Postgres95 run on?

	The authors have compiled and tested Postgres95 on the following
	platforms:
	
	- OSF 2.1, 3.0, 3.2/Alpha with cc and gcc 2.7.0
	- Ultrix 4.4/DECStation with cc and gcc 2.7.0 (libdl package required)
	- SunOS 4.1.3/SPARC with gcc 2.7.0
	- Solaris 2.4/SPARC with gcc 2.7.0
	- HP-UX 9.0/HP 9000/700 with cc. (It is possible to compile Postgres95
	  with gcc but the dynamic loader will not work.)
	- Linux/Intel x86, ELF format:  kernel 1.2.10, gcc 2.6.3 

	The following ports are bundled with the Postgres95 distribution. The
	authors do not have handy access to these platforms but the
	ports have been tested by the others.

	- BSD44_derived/i386. Tested on NetBSD 1.0.  Should also work
	  for FreeBSD and BSD/OS.
	- AIX/IBM RS6000 
	- IRIX 5/SGI. Tested on IRIX 5.3.

1.3)	Where can I get Postgres95?
	
	The primary anonymous ftp site for postgres95 is:
		ftp://s2k-ftp.cs.berkeley.edu/pub/postgres95

	Postgres95 is also mirrored at the following sites:

		ftp://zarquon.mathi.uni-heidelberg.de/pub/Apps/postgres95
		ftp://ftp.jaist.ac.jp/pub/dbms/postgres95
		ftp://scitsc.wlv.ac.uk/pub/postgres
		ftp://luga.or.at/pub/linux/postgres95
		ftp://sunsite.icm.edu.pl/pub/unix/postgres95/
		ftp://sunsite.mff.cuni.cz/Apps/Database/Postgres95
		ftp://ftp.vnet.net/pub/postgres95
		ftp://ftp.ivc.cc.ca.us/pub/Mirrors/Postgres95
		ftp://tika.ndim.edrc.cmu.edu/pub/postgres95

1.4)	What's the copyright on Postgres95?

	Postgres95 is subject to the following COPYRIGHT.
	
POSTGRES95 Data Base Management System

Copyright (c) 1994-6 Regents of the University of California

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 Postgres95

	There is *NO* official support for Postgres95.  It is
	maintained through volunteer effort only.

	With the generosity of the Jason Wright and others at Vnet,
        the postgres95 mailing list now has a new home --
	postgres95@postgres95.vnet.net.  It is available for
	discussion of matters pertaining to Postgres95, including but
	not limited to bug reports and fixes. For info on how to
	subscribe, send a mail with the lines in the body (not the
	subject line): 
		help
		info postgres95
	to 
		majordomo@postgres95.vnet.net

	There is also a digest list available.  To subscribe to this list,
	send email to majordomo@postgres95.vnet.net with a BODY of:
		subscribe postgres95-digest
	Digests are sent out to members of this list whenever the main list has
	received around 30k of messages.

	Archives and digests of the new mailing list at Vnet can be found at:
		ftp://postgres95.vnet.net/pub/postgres95/archives
		ftp://postgres95.vnet.net/pub/postgres95/digests

	Additional information about Postgres95 can be found via the
	postgres95 WWW home page at:
		http://s2k-ftp.cs.berkeley.edu:8000/postgres95

	or its mirror sites:
		http://www.vnet.net/postgres95/
		http://tika.ndim.edrc.cmu.edu/postgres95/
		http://www.luga.or.at/postgres95
		http://sunsite.icm.edu.pl/pub/unix/postgres95/
		http://sunsite.mff.cuni.cz/postgres95

1.6)	Future releases of Postgres95

	The latest release of postgres95 is version 1.01.  No date
	has been set for any future releases.

1.7)	Is there a commercial version of Postgres95?
 
	Illustra Information Technology sells an object-relational
	DBMS called Illustra that was originally based on postgres.
	Illustra has cosmetic similarities to postgres95 but has more
	features, is more robust, performs better, and offers real
	documentation and support.  On the flip side, it costs money.
	For more information, contact sales@illustra.com

1.8)	What documentation is available for Postgres95?

	A user manual, reference manual, and some small test examples
        are included in the distribution.  Beyond that, there's	no
        additional documentation available at this time.   (Please contact 
	the authors if you are willing to help write documentation)

1.9)	What version of SQL does Postgres95 use?

	Postgres95 supports a subset of SQL-92.  It has most of the
	important constructs but lacks some of the functionality.
	The most visible differences are:
		- no support for primary keys or column constraints
		- no support for nested subqueries
		- no HAVING clause under a GROUP BY

	On the other hand, you get to create user-defined types,
	functions, inheritance etc.  If you're willing to help with
        postgres95 coding, eventually we can also add the missing
        features listed above. 
	
1.10)	Does Postgres95 work with databases from earlier versions of postgres?
	
Postgres95 v1.01 is compatible with databases created with v1.0.
Please follow the directions in the MIGRATION_1.0_to_1.01 file.
	
1.11)   How many people use Postgres95?

	Since we don't have any licensing or registration scheme, it's
	impossible to tell.  We do know that several hundred copies of
	postgres95 v1.0 have been downloaded, and that there many
	hundreds of subscribers to the mailing list.  
	
----------------------------------------------------------------------
Section 2:	Installation Questions
----------------------------------------------------------------------

2.1)	I get the error "cpp: command not found"  when I try to compile
the backend. 

	Edit the src/backend/utils/Gen_fmgrtab.sh script to include the path
	for the cpp for your particular site. 

2.2)	I get 'yy_flush_buffer undefined' when I try to compile the backend

	Use a more recent version of flex, like 2.5.2 or later

2.3)	initdb doesn't run

	* check to see that you have the proper paths set
	* check that the 'postgres' user owns all the right files
	* ensure that there are files in $PGDATA/files, and that they 
	  are non-empty.  If they aren't, then "gmake install" failed for
	  some reason   

2.4)	when I start up the postmaster, I get
		"FindBackend: could not find a backend to execute..."
		"postmaster: could not find backend to execute..."

	You probably do not have the right path set up. the 'postgres'
	executable needs to be in your path.  

2.5)	The system seems to be confused about commas, decimal points, and
date formats.

	Check your locale configuration. postgres95 uses the locale
	settings of the user that ran the postmaster process.  Set those
	accordingly for your operating environment. 

2.6)	How do I install postgres95 somewhere other than /usr/local/postgres95?

	You need to manually edit the paths in src/Makefile.global to 
	your site configuration.

2.7)    The backend compiled successfully, but compiling libpq resulted
	in a complaint:	"libpq/pqcomm.h" not found when compiling fe-auth.c.

	You've probably installed postgres95 somewhere other than
	/usr/local/postgres, but didn't edit the src/Makefile.global
	accordingly.  See question 2.6.

2.8)	Where can I find the bug fixes for postgres95?

	The bug list and patches are listed at the following web page:
  	   http://s2k-ftp.cs.berkeley.edu:8000/postgres95/www/pglite5.html

	The patches should be applied in the order listed.  The patch files
	can be ftp'ed directly from the directory:
  	   ftp://s2k-ftp.cs.berkeley.edu:8000/postgres95/www/bugs

2.9)	I can't apply the patches even though everything looks like it should
	work. 

	If you cut and paste directly off your web browser, tabs and 
	whitespaces may not be preserved properly.  Use the 'save as file'
	option from your web browser instead.

2.10)	When I run postmaster, I get a Bad System Call core dumped message.

	It could be a variety of problems, but first check to see that you
	have system V extensions installed on your kernel.  Postgres95 requires
	kernel support for shared memory.

2.11)   I get the error message "obj/fmgr.h: No such file or directory"

	This indicates that you did not generate the file fmgr.h
	properly.  Something failed in the running of the
	src/backend/utils/Gen_fmgrtab.sh script.  Check to see the
        paths used in that script is appropriate to your system.
 
----------------------------------------------------------------------
Section 3:	Postgres95 Features
----------------------------------------------------------------------

3.1)	How do I specify a KEY or other constraints on a column?

	Column constraints are not supported in postgres95.
	As a consequence, the system does not check for duplicates. 
	
3.2)	Does Postgres95 support nested subqueries?

	No, postgres95 does not support nested subqueries.

3.3)	How do I define a unique indices?

	Postgres95 does not support unique indices.  Defining an index does
	not preclude insertion of duplicate index key values.

3.4)	I've having a lot of problems with using rules.
	
	Currently, the rule system in postgres95 is mostly broken.  It
	works enough to support the view mechanism, but that's about it.  Use
	postgres95 rules at your own peril.

3.5)	I can't seem to write into the middle of large objects reliably.

	The Inversion large object system in postgres95 is also
	mostly broken.  It works well enough for storing large wads
	of data and reading them back out, but the implementation has
	some underlying problems.  Use postgres95 large objects at
	your own peril. 

3.6)	Does postgres95 have a graphical user interface?  A report
generator? A embedded query language interface?  

	No. No. No.  Not in the official distribution at least.  Some
	users have reported some success at using 'pgbrowse' and 'onyx' as
	frontends to postgres95.  Several contributions are working on
        tk based frontend tools.  Ask on the mailing list.
	
3.7)	How can I write client applications to Postgres95?

	Postgres95 supports a C-callable library interface called libpq
	as well as a Tcl-based library interface called libtcl.

	Others have contributed a perl interface and a WWW gateway
	to postgres95.  See the postgres95 home pages for more details. 

3.8)	How do I prevent other hosts from accessing my Postgres95
	backend?
	
	Host-based authentication has been added to version 1.01.  
        Modify the file $PGDATA/pg_hba accordingly.

3.9)	How do I set up a pg_group?
	
	Currently, there is no easy interface to set up user groups.
	You have to explicitly insert/update the pg_group table.  For example:

	jolly=> insert into pg_group (groname, grosysid, grolist)
	jolly=>     values ('posthackers', '1234', '{5443, 8261}');
	INSERT 548224
	jolly=> grant insert on foo to group posthackers;
	CHANGE
	jolly=> 

	The fields in pg_group are:
		groname:  the group name.  This a char16 and should
			  be purely alphanumeric.  Do not include underscores
			  or other punctuation.
		grosysid: the group id.  This is an int4. 
			  This should be unique for each group.
		grolist:   the list of pg_user id's that belong in the group.
			  This is an int4[].

3.10)  What is the exact difference between binary cursors and normal cursors?

Normal cursors return data back in ASCII format.  Since data is stored
natively in binary format, the system must do a conversion to produce
the ASCII format.  In addition, ASCII formats are often large in size
than binary format.  Once the attributes come back in ASCII, often the
client application then has to convert it to a binary format to
manipulate it anyway. 

Binary cursors give you back the data in the native binary
representation.  Thus, binary cursors will tend to be a little faster
since there's less overhead of conversion. 

However, ASCII is architectural neutral whereas binary representation
can differ between different machine architecture.  Thus, if your client
machine uses a different representation than you server machine, getting
back attributes in binary format is probably not what you want.  Also,
if your main purpose is displaying the data in ASCII, then getting it
back in ASCII will save you some effort on the client side.

3.11)	Why doesn't the != operator work?
	
	SQL specifies <> as the inequality operator, and that is what
we have defined for the built-in types.  You are free, however, to
extend postgres95 to include the != operator if you like.  

3.12)	What is a R-tree index and what is it used for?

An r-tree index is used for indexing spatial data. A hash index can't
handle range searches. A B-tree index only handles range searches in a
single dimension. R-tree's can handle multi-dimensional data.  For
example, if a R-tree index can be built on an attribute of type
'point', the system can more efficient answer queries like select all
points within a bounding rectangle.

The canonical paper that describes the original R-Tree design is:

Guttman, A. "R-Trees: A Dynamic Index Structure for Spatial Searching."
Proc of the 1984 ACM SIGMOD Int'l Conf on Mgmt of Data, 45-57.

You can also find this paper in Stonebraker's "Readings in Database Systems"

3.13)	What is the maximum size for a tuple?

Tuples are limited to 8K bytes.  Taking into account system attributes
and other overhead, one should stay well shy of 8,000 bytes to be on
the safe side.   To use attributes larger than 8K, try using the large
objects interface.

3.14)	How do I update a column to be NULL?

Currently, there is no way to do this.

3.15)   I defined indices but my queries don't seem to make use of them. Why?

Postgres95 does not automatically maintain statistics.  One has to
make an explicit 'vacuum' call to update the statistics.   After
statistics are updated, the optimizer has a better shot at using
indices.  Note that the optimizer is limited and does not use indices
in some circumstances (such as OR clauses).

3.16)	Are there ODBC drivers for Postgres95?

Not as of yet.  Cees de Groot (C.deGroot@inter.NL.net) and possibly
others are working on one.  Please contact him if you would like to help.  

3.17)	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. 

3.18)   How do I do regular expression searches?  case-insensitive regexp searching?

Postgres95 supports the SQL LIKE syntax as well as more general
regular expression searching with the ~ operator.  The !~ is the
negated regexp operator.  ~* and !~* are the case-insensitive regular
expression operators.

----------------------------------------------------------------------
Section 4:	Extending Postgres95
----------------------------------------------------------------------

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 standalone 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 Postgres95.  

	Please share them with other postgres95 users.  Send your
	extensions to mailing list, and they will eventually end up in
	the contrib/ subdirectory.

4.4)	How do I write a C function to return a tuple?

	This requires extreme wizardry, so extreme that the authors
	have not ever tried it, though in principle it can be done.  
	The short answer is ... you can't.   This capability is
	forthcoming in the future.

----------------------------------------------------------------------
Section 5:	Bugs
----------------------------------------------------------------------

5.1)	How do I find out about bug fixes?

	The directory s2k-ftp.cs.berkeley.edu:/pub/postgres95/www/bugs
	contains patches for the latest release.

5.2)	How do I make a bug report?

	First, check to see that your bug is not one that has already
	been fixed (question 5.1).  Then, fill out the "bug-template"
	file and send it to
		postgres95@postgres95.vnet.net

	Since there is no official support for postgres95, bug reports
	may or may not be attended to.  Bug reports that do not follow
        the bug-template format usually have insufficient information and are
        summarily ignored.

        Please do not send bug reports directly to the authors.  We
	already monitor the mailing lists closely.

