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diff --git a/doc/FAQ b/doc/FAQ new file mode 100644 index 00000000000..42df6d34aa0 --- /dev/null +++ b/doc/FAQ @@ -0,0 +1,827 @@ +================================================== +Frequently Asked Questions (FAQ) for Postgres95 +================================================== +last updated: Sun Aug 11 01:35:34 EDT 1996 + +current maintainer: Bruce Momjian (maillist@candle.pha.pa.us) +original author: Jolly Chen (jolly@cs.berkeley.edu) + +changes in this version (* = modified, + = new): +* 1.8) What documentation is available for Postgres95? +* 3.13) What is the maximum size for a tuple? +* 3.14) I defined indices but my queries don't seem to make use of them. Why? +* 3.37) What is the time-warp feature and how does it relate to vacuum? ++ 3.38) How do I tune the database engine for better performace? + +This file is divided approximately as follows: +1.*) General questions +2.*) Installation questions +3.*) Postgres95 Features questions +4.*) Questions about extending Postgres95 +5.*) Bugs + +Questions answered: +1.1) What is Postgres95? +1.2) What does Postgres95 run on? +1.3) Where can I get Postgres95? +1.4) What's the copyright on Postgres95? +1.5) Support for Postgres95 +1.6) Future releases of Postgres95 +1.7) Is there a commercial version of Postgres95? +1.9) What version of SQL does Postgres95 use? +1.10) Does Postgres95 work with databases from earlier versions of postgres? +1.11) How many people use Postgres95? +2.1) I get the error "cpp: command not found" when I try to compile +2.2) I get 'yy_flush_buffer undefined' when I try to compile the backend +2.3) initdb doesn't run +2.4) when I start up the postmaster, I get +2.5) The system seems to be confused about commas, decimal points, and +2.6) How do I install postgres95 somewhere other than /usr/local/postgres95? +2.7) The backend compiled successfully, but compiling libpq resulted + in a complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c. +2.8) Where can I find the bug fixes for postgres95? +2.9) I can't apply the patches even though everything looks like it should + work. +2.10) When I run postmaster, I get a Bad System Call core dumped message. +2.11) I get the error message "obj/fmgr.h: No such file or directory" +2.12) When I try to start the postmaster, I get IpcMemoryCreate errors. +2.13) I get the strange make errors right at the beginning: +2.14) I have changed a source file, but a recompile does not see the +3.1) How do I specify a KEY or other constraints on a column? +3.2) Does Postgres95 support nested subqueries? +3.3) How do I define a unique indices? +3.4) I've having a lot of problems with using rules. +3.5) I can't seem to write into the middle of large objects reliably. +3.6) Does postgres95 have a graphical user interface? A report +3.7) How can I write client applications to Postgres95? +3.8) How do I prevent other hosts from accessing my Postgres95 +3.9) How do I set up a pg_group? +3.10) What is the exact difference between binary cursors and normal cursors? +3.11) Why doesn't the != operator work? +3.12) What is a R-tree index and what is it used for? +3.13) What is the maximum size for a tuple? +3.14) I defined indices but my queries don't seem to make use of them. Why? +3.15) Are there ODBC drivers for Postgres95? +3.16) How do I use postgres for multi-dimensional indexing (> 2 dimensions)? +3.17) How do I do regular expression searches? case-insensitive + regexp searching? +3.18) I can't access the database as the 'root' user. +3.19) I experienced a server crash during a vacuum. How do I remove the + lock file? +3.20) What is the difference between the various character types? +3.21) In a query, how do I detect if a field is NULL? +3.22) How do I see how the query optimizer is evaluating my query? +3.23) How do I create a serial field? +3.24) How do I create a multi-column index? +3.25) What are the temp_XXX files in my database directory? +3.26) Why are my table files not getting any smaller after a delete? +3.27) Why can't I connect to my database from another machine? +3.28) I get the error 'default index class unsupported' when creating an + index. How do I do it? +3.29) Why does creating an index crash the backend server? +3.30) How do I specify a decimal constant as a float8, or a string as a text? +3.31) How do I find out what indexes or operations are defined in the + database? +3.32) My database is corrupt. I can't do anything. What should I do? +3.33) Createdb, destroydb, createuser,destroyuser don't run. Why? +3.34) Why does 'createuser' return 'unexpected last match in input()'? +3.35) All my servers crash under concurrent table access. Why? +3.36) What tools are available for hooking postgres to Web pages? +3.37) What is the time-warp feature and how does it relate to vacuum? +3.38) How do I tune the database engine for better performace? +4.1) I wrote a user-defined function and when I run it in psql, it + dumps core. +4.2) I get messages of the type NOTICE:PortalHeapMemoryFree: 0x402251d0 +4.3) I've written some nifty new types and functions for Postgres95. +4.4) How do I write a C function to return a tuple? +5.1) How do I find out about bug fixes? +5.2) How do I make a bug report? + + +---------------------------------------------------------------------- +Section 1: General Questions +---------------------------------------------------------------------- + +1.1) What is Postgres95? + + Postgres95 is an enhancement of the POSTGRES database + management system, a next-generation DBMS research prototype. + While Postgres95 retains the powerful data model and rich data + types of POSTGRES, it replaces the PostQuel query language with an + extended subset of SQL. Postgres95 is free and the complete + source is available. + + Postgres95 development is being performed by a team of Internet + developers who all subscribe to the Postgres95 development mailing + list. The current coordinator is Marc G. Fournier (scrappy@ki.net). + (See below on how to join). This team is now responsible for all + current and future development of Postgres95. + + The authors of Postgres95 1.01 were Andrew Yu and Jolly Chen. + Many others have contributed to the porting, testing, debugging and + enhancement of the code. The original Postgres code, from which + Postgres95 is derived, was the effort of many graduate + students, undergraduate students, and staff programmers + working under the direction of Professor Michael Stonebraker + at the University of California, Berkeley. + +1.2) What does Postgres95 run on? + + The authors have compiled and tested Postgres95 on the following + platforms(some of these compiles require gcc 2.7.0): + + - DEC Alpha AXP on OSF/1 2.0 + - HP PA-RISC on HP-UX 9.0 + - i386 Solaris + - SUN SPARC on Solaris 2.4 + - SUN SPARC on SunOS 4.1.3 + - DEC MIPS on Ultrix 4.4 + - Intel x86 on Linux 1.2 and Linux ELF + - OSs derived from 4.4-lite BSD (NetBSD, FreeBSD) + - IBM on AIX 3.2.5 + - BSD/OS 2.0, 2.01 & 2.1 + - SGI MIPS on IRIX 5.3 + + The following ports are bundled with the Postgres95 distribution. The + authors do not have handy access to these platforms but the + ports have been tested by the others. + + - Motorola MC68K or Intel x86 on NeXTSTEP 3.2 + - Intel x86 on Intel SVR4 + +1.3) Where can I get Postgres95? + + The primary anonymous ftp site for postgres95 is: + + ftp://ftp.ki.net/pub/postgres95 + + A mirror site exists at: + + ftp://postgres95.vnet.net/pub/postgres95 + +1.4) What's the copyright on Postgres95? + + Postgres95 is subject to the following COPYRIGHT. + +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 from the original + maintainers or from University of California, Berkeley. It is + maintained through volunteer effort only. + + With the generosity of the Jason Wright and others at Vnet, + the postgres95 mailing list now has a new home -- + postgres95@postgres95.vnet.net. It is available for + discussion of matters pertaining to Postgres95, including but + not limited to bug reports and fixes. For info on how to + subscribe, send a mail with the lines in the body (not the + subject line): + help + info postgres95 + to + majordomo@postgres95.vnet.net + + There is also a digest list available. To subscribe to this list, + send email to majordomo@postgres95.vnet.net with a BODY of: + subscribe postgres95-digest + Digests are sent out to members of this list whenever the main list has + received around 30k of messages. + + Archives and digests of the new mailing list at Vnet can be found at: + ftp://postgres95.vnet.net/pub/postgres95/archives + ftp://postgres95.vnet.net/pub/postgres95/digests + + There is also a developers mailing list available. To subscribe to + this list, send email to pg95-dev-request@ki.net with a BODY of: + + subscribe pg95-dev + + Additional information about Postgres95 can be found via the + postgres95 WWW home page at: + http://www.ki.net/postgres95 + +1.6) Future releases of Postgres95 + + The latest release of postgres95 is version 1.02. + +1.7) Is there a commercial version of Postgres95? + + Illustra Information Technology (a wholly owned subsidiary of + Informix Software, Inc.) sells an object-relational + DBMS called Illustra that was originally based on postgres. + Illustra has cosmetic similarities to postgres95 but has more + features, is more robust, performs better, and offers real + documentation and support. On the flip side, it costs money. + For more information, contact sales@illustra.com + +1.8) What documentation is available for Postgres95? + + A user manual, manual pages, and some small test examples + are included in the distribution. The www page contains + pointers to an implementation guide and five papers written + about postgres design concepts and features. + +1.9) What version of SQL does Postgres95 use? + + Postgres95 supports a subset of SQL-92. It has most of the + important constructs but lacks some of the functionality. + The most visible differences are: + - no support for primary keys or column constraints + - no support for nested subqueries + - no HAVING clause under a GROUP BY + + On the other hand, you get to create user-defined types, + functions, inheritance etc. If you're willing to help with + postgres95 coding, eventually we can also add the missing + features listed above. + +1.10) Does Postgres95 work with databases from earlier versions of postgres? + + Postgres95 v1.02 is compatible with databases created with v1.01. + Those upgrading from 1.0 to 1.02 should read the directions in the + MIGRATION_1.0_TO_1.02 directory. + +1.11) How many people use Postgres95? + + Since we don't have any licensing or registration scheme, it's + impossible to tell. We do know hundreds copies of postgres95 + v1.* have been downloaded, and that there many hundreds of + subscribers to the mailing lists. + +---------------------------------------------------------------------- +Section 2: Installation Questions +---------------------------------------------------------------------- + +2.1) I get the error "cpp: command not found" when I try to compile +the backend. + + Edit the src/backend/utils/Gen_fmgrtab.sh script to include the path + for the cpp for your particular site. + +2.2) I get 'yy_flush_buffer undefined' when I try to compile the backend + + Use a more recent version of flex, version 2.5.2. Version 2.5.3 + has a known bug. + +2.3) initdb doesn't run + + * check to see that you have the proper paths set + * check that the 'postgres' user owns all the right files + * ensure that there are files in $PGDATA/files, and that they + are non-empty. If they aren't, then "gmake install" failed for + some reason + +2.4) when I start up the postmaster, I get + "FindBackend: could not find a backend to execute..." + "postmaster: could not find backend to execute..." + + You probably do not have the right path set up. the 'postgres' + executable needs to be in your path. + +2.5) The system seems to be confused about commas, decimal points, and +date formats. + + Check your locale configuration. postgres95 uses the locale + settings of the user that ran the postmaster process. Set those + accordingly for your operating environment. + +2.6) How do I install postgres95 somewhere other than /usr/local/postgres95? + + You need to manually edit the paths in src/Makefile.global to + your site configuration. + +2.7) The backend compiled successfully, but compiling libpq resulted + in a complaint: "libpq/pqcomm.h" not found when compiling fe-auth.c. + + You've probably installed postgres95 somewhere other than + /usr/local/postgres, but didn't edit the src/Makefile.global + accordingly. See question 2.6. + +2.8) Where can I find the bug fixes for postgres95? + + The patches should be applied in the order listed. The patch files + can be ftp'ed directly from the directory: + ftp://ftp.ki.net/pub/postgres95 + +2.9) I can't apply the patches even though everything looks like it should + work. + + If you cut and paste directly off your web browser, tabs and + whitespaces may not be preserved properly. Use the 'save as file' + option from your web browser instead. + +2.10) When I run postmaster, I get a Bad System Call core dumped message. + + It could be a variety of problems, but first check to see that you + have system V extensions installed on your kernel. Postgres95 + requires kernel support for shared memory. + +2.11) I get the error message "obj/fmgr.h: No such file or directory" + + This indicates that you did not generate the file fmgr.h + properly. Something failed in the running of the + src/backend/utils/Gen_fmgrtab.sh script. Check to see the + paths used in that script is appropriate to your system. + +2.12) When I try to start the postmaster, I get IpcMemoryCreate errors. + + You either do not have shared memory configured properly in kernel + or you need to enlarge the shared memory available in the kernel. + The exact amount you need depends on your architecture and how + many buffers you configure postmaster to run with. For most + systems, with default buffer sizes, you need a minimum of ~760K. + +2.13) I get the strange make errors right at the beginning: + warning: NUL character seen; rest of line ignored + *** missing separator. Stop. + or + Is a directory. Stop. + + Eliminate any whitespaces at the end of the PORTNAME line in + Makefile.global. Extraneous tabs or spaces will confuse the make + templates. + +2.14) I have changed a source file, but a recompile does not see the +change? + + The Makefiles do not have the proper dependencies. You have to + do a 'make clean' and then another 'make'. + +---------------------------------------------------------------------- +Section 3: Postgres95 Features +---------------------------------------------------------------------- + +3.1) How do I specify a KEY or other constraints on a column? + + Column constraints are not supported in postgres95. + As a consequence, the system does not check for duplicates. + +3.2) Does Postgres95 support nested subqueries? + + Subqueries are not implemented, but they can be simulated using sql + functions. + +3.3) How do I define a unique indices? + + Postgres95 does not support unique indices. Defining an index does + not preclude insertion of duplicate index key values. + +3.4) I've having a lot of problems with using rules. + + Currently, the rule system in postgres95 is mostly broken. It + works enough to support the view mechanism, but that's about it. Use + postgres95 rules at your own peril. + +3.5) I can't seem to write into the middle of large objects reliably. + + The Inversion large object system in postgres95 is also + mostly broken. It works well enough for storing large wads + of data and reading them back out, but the implementation has + some underlying problems. Use postgres95 large objects at + your own peril. + +3.6) Does postgres95 have a graphical user interface? A report +generator? A embedded query language interface? + + No. No. No. Not in the official distribution at least. Some + users have reported some success at using 'pgbrowse' and 'onyx' as + frontends to postgres95. Several contributions are working on + tk based frontend tools. Ask on the mailing list. + +3.7) How can I write client applications to Postgres95? + + Postgres95 supports a C-callable library interface called libpq + as well as a Tcl-based library interface called libtcl. + + Others have contributed a perl interface and a WWW gateway + to postgres95. See the postgres95 home pages for more details. + +3.8) How do I prevent other hosts from accessing my Postgres95 + backend? + + Use host-based authentication by modifying the file + $PGDATA/pg_hba accordingly. + +3.9) How do I set up a pg_group? + + Currently, there is no easy interface to set up user groups. + You have to explicitly insert/update the pg_group table. For example: + + jolly=> insert into pg_group (groname, grosysid, grolist) + jolly=> values ('posthackers', '1234', '{5443, 8261}'); + INSERT 548224 + jolly=> grant insert on foo to group posthackers; + CHANGE + jolly=> + + The fields in pg_group are: + groname: the group name. This a char16 and should + be purely alphanumeric. Do not include underscores + or other punctuation. + grosysid: the group id. This is an int4. + This should be unique for each group. + grolist: the list of pg_user id's that belong in the group. + This is an int4[]. + +3.10) What is the exact difference between binary cursors and normal cursors? + + Normal cursors return data back in ASCII format. Since data is stored + natively in binary format, the system must do a conversion to produce + the ASCII format. In addition, ASCII formats are often large in size + than binary format. Once the attributes come back in ASCII, often the + client application then has to convert it to a binary format to + manipulate it anyway. + + Binary cursors give you back the data in the native binary + representation. Thus, binary cursors will tend to be a little faster + since there's less overhead of conversion. + + However, ASCII is architectural neutral whereas binary representation + can differ between different machine architecture. Thus, if your client + machine uses a different representation than you server machine, getting + back attributes in binary format is probably not what you want. Also, + if your main purpose is displaying the data in ASCII, then getting it + back in ASCII will save you some effort on the client side. + +3.11) Why doesn't the != operator work? + + SQL specifies <> as the inequality operator, and that is what + we have defined for the built-in types. You are free, however, to + extend postgres95 to include the != operator if you like. + +3.12) What is a R-tree index and what is it used for? + + An r-tree index is used for indexing spatial data. A hash index can't + handle range searches. A B-tree index only handles range searches in a + single dimension. R-tree's can handle multi-dimensional data. For + example, if a R-tree index can be built on an attribute of type + 'point', the system can more efficient answer queries like select all + points within a bounding rectangle. + + The canonical paper that describes the original R-Tree design is: + + Guttman, A. "R-Trees: A Dynamic Index Structure for Spatial Searching." + Proc of the 1984 ACM SIGMOD Int'l Conf on Mgmt of Data, 45-57. + + You can also find this paper in Stonebraker's "Readings in Database + Systems" + +3.13) What is the maximum size for a tuple? + + Tuples are limited to 8K bytes. Taking into account system attributes + and other overhead, one should stay well shy of 8,000 bytes to be on + the safe side. To use attributes larger than 8K, try using the large + objects interface. + + Tuples do not cross 8k boundaries so a 5k tuple will require 8k + of storage. + +3.14) I defined indices but my queries don't seem to make use of them. Why? + + Postgres95 does not automatically maintain statistics. One has to + make an explicit 'vacuum' call to update the statistics. After + statistics are updated, the optimizer has a better shot at using + indices. Note that the optimizer is limited and does not use indices + in some circumstances (such as OR clauses). + + If the system still does not see the index, it is probably because you + have created an index on a field with the improper *_ops type. For + example, you have created a CHAR(4) field, but have specified a + char_ops index type_class. + + See the create_index manual page for information on what type classes + are available. It must match the field type. + + Postgres does not warn the user when the improper index is created. + + Indexes not used for ORDER BY operations. + +3.15) Are there ODBC drivers for Postgres95? + + PostODBC is available as an ODBC driver for Postgres95. + + For all people being interested in PostODBC, a freely available ODBC + driver for Postgres95, there are now two mailing lists devoted to the + discussion of PostODBC. The mailing lists are: + + postodbc-users@listserv.direct.net + and + postodbc-developers@listserv.direct.net + + these lists are ordinary majordomo mailing lists. You can subscribe + by sending a mail to + + majordomo@listserv.direct.net + +3.16) How do I use postgres for multi-dimensional indexing (> 2 dimensions)? + + Builtin R-Trees can handle polygons and boxes. In theory, R-trees can + be extended to handle higher number of dimensions. In practice, + extending R-trees require a bit of work and we don't currently have + any documentation on how to do it. + +3.17) How do I do regular expression searches? case-insensitive +regexp searching? + + Postgres95 supports the SQL LIKE syntax as well as more general + regular expression searching with the ~ operator. The !~ is the + negated regexp operator. ~* and !~* are the case-insensitive regular + expression operators. + +3.18) I can't access the database as the 'root' user. + + You should not create database users with user id 0(root). They will + be unable to access the database. This is a security precaution + because of the ability of any user to dynamically link object modules + into the database engine. + +3.19) I experienced a server crash during a vacuum. How do I remove the +lock file? + + If the server crashes during a vacuum command, chances are it will + leave a lock file hanging around. Attempts to re-run the vacuum + command result in + WARN:can't create lock file -- another vacuum cleaner running? + + If you are sure that no vacuum is actually running, you can remove the + file called "pg_vlock" in your database directory (which is + $PGDATA/base/<dbName>) + +3.20) What is the difference between the various character types? + +Type Internal Name Notes +-------------------------------------------------- +CHAR char 1 character } +CHAR2 char2 2 characters } +CHAR4 char4 4 characters } optimized for a fixed length +CHAR8 char8 8 characters } +CHAR16 char16 16 characters } +CHAR(#) bpchar blank padded to the specified fixed length +VARCHAR(#) varchar size specifies maximum length, no padding +TEXT text length limited only by maximum tuple length +BYTEA bytea variable-length array of bytes + + Remember, you need to use the internal name when creating indexes + on these fields or when doing other internal operations. + + The last four types above are "varlena" types (i.e. the first + four bytes is the length, followed by the data). CHAR(#) and + VARCHAR(#) allocate the maximum number of bytes no matter how + much data is stored in the field. TEXT and BYTEA are the only + character types that have variable length on the disk. + +3.21) In a query, how do I detect if a field is NULL? + + Postgres95 has two builtin keywords, "isnull" and "notnull" (note no + spaces). For example: + select * from tbl where field isnull + will return rows from tbl where the field is null valued. + +3.22) How do I see how the query optimizer is evaluating my query? + + Place the word 'EXPLAIN' at the beginning of the query, for example: + + EXPLAIN SELECT * FROM table1 WHERE age = 23; + +3.23) How do I create a serial field? + + There is no way to create a serial or unique field in Postgres95. You + can use each row's oid field as a unique value. However, if you need + to dump and reload the database, you will be assigned new oid's. + There is no way to restore the original oids. + + One valid way of doing this is to create a function: + + create table my_oids (f1 int4); + insert into my_oids values (1); + create function new_oid () returns int4 as + 'update my_oids set f1 = f1 + 1; select f1 from my_oids; ' + language 'sql'; + + then: + + create table my_stuff (my_key int4, value text); + insert into my_stuff values (new_oid(), 'hello'); + + However, keep in mind there is a race condition here where one + server could do the update, then another one do an update, and + they both could select the same new id. This statement should + be performed within a transaction. + +3.24) How do I create a multi-column index? + + You can not directly create a multi-column index using create index. + You need to define a function which acts on the multiple columns, then + use create index with that function. + +3.25) What are the temp_XXX files in my database directory? + + They are temp_ files generated by the query executor. For example, + if a sort needs to be done to satisfy an ORDER BY, some temp files are + generated as a result of the sort. + + If you have no transactions or sorts running at the time, it is safe to + delete the temp_ files. + +3.26) Why are my table files not getting any smaller after a delete? + + If you run vacuum, unused rows will be marked for reuse, but the file + blocks are not released. We could move the unused rows to the end of + the file and use ftruncate() to decrease the file size, but no one has + implemented this yet. + +3.27) Why can't I connect to my database from another machine? + + The default configuration allows only connections from tcp/ip host + localhost. You need to add a host entry to the file + postgres95/data/pg_hba. + +3.28) I get the error 'default index class unsupported' when creating an +index. How do I do it? + + You probably used: + + create index idx1 on person using btree (name); + + Postgres95 indexes are extensible, and therefore you must specify a + class_type when creating an index. Read the manual page for create + index (called create_index). + +3.29) Why does creating an index crash the backend server? + + You have probably defined an incorrect *_ops type class for the field + you are indexing. + +3.30) How do I specify a decimal constant as a float8, or a string as a text? + + Use the :: operator. It is needed only when the default promotion + rules fail. i.e.: + + insert into tab1 values (4.23::float8, '2343'::text) + +3.31) How do I find out what indexes or operations are defined in the +database? + + Run the file postgres95/src/tutorial/syscat.source. It illustrates + many of the 'select's needed to get information out of the database + system tables. + +3.32) My database is corrupt. I can't do anything. What should I do? + + The 1.02 release has a README file and utility that describes a + possible cause of the problem and a workaround. See the file + postgres95/contrib/zap_ltv/README for more information. Also + please contact the README author to help generate a complete + fix for this bug. + + This bug may be fixed in 1.02. + +3.33) Createdb, destroydb, createuser,destroyuser don't run. Why? + + Release 1.02 does not have this problem. + + The 1.01 release of postgres95 uses a variable called PAGER to + filter the output of SELECT statements. Unfortunately, this + PAGER is used even when the standard output is not a terminal. + Upgrade to 1.02, due out August 1996, or undefine your PAGER + variable. There is also a patch located in the July archives of + the mailing list that fixes this problem on 1.01. + +3.34) Why does 'createuser' return 'unexpected last match in input()'? + + You have compile postgres with flex version 2.5.3. There is bug + in this version of flex. Use flex version 2.5.2 instead. There + is a doc/README.flex file which will properly patch the flex 2.5.3 + source code. + +3.35) All my servers crash under concurrent table access. Why? + + This problem can be caused by a kernel that is not configured to + support semaphores. + +3.36) What tools are available for hooking postgres to Web pages? + + For web integration, PHP/FI is an excellent interface. The URL for + that is http://www.vex.net/php/ + + PHP is great for simple stuff, but for more complex stuff, some + still use the perl interface and CGI.pm. + + An example of using WWW with C to talk to Postgres is can be + tried at: + + http://www.ki.net/~mlc + +3.37) What is the time-warp feature and how does it relate to vacuum? + + Postgres95 handles data changes differently than most database + systems. When a row is changed in a table, the original row + is marked with the time it was changed, and a new row is created + with the current data. By default, only current rows are used + in a table. If you specify a date/time after the table name in + a FROM clause, you can access the data that was current at that + time, i.e. + + SELECT * + FROM employees ['July 24, 1996 09:00:00'] + + 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. + +3.38) How do I tune the database engine for better performace? + + 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. + + + +---------------------------------------------------------------------- +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 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 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 ftp.ki.net:/pub/postgres95 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: + + pg95-dev@ki.net + + This is the address of the developers mailing list. + |