From 510a47a91e9466d09c31f5718a28de42dda9f514 Mon Sep 17 00:00:00 2001 From: Bruce Momjian Date: Sat, 4 Dec 2004 04:12:11 +0000 Subject: [PATCH] Properl format HTML in developer's FAQ. --- doc/src/FAQ/FAQ_DEV.html | 1397 +++++++++++++++++++------------------- 1 file changed, 695 insertions(+), 702 deletions(-) diff --git a/doc/src/FAQ/FAQ_DEV.html b/doc/src/FAQ/FAQ_DEV.html index ab898d6dd6..b2f2976e71 100644 --- a/doc/src/FAQ/FAQ_DEV.html +++ b/doc/src/FAQ/FAQ_DEV.html @@ -1,235 +1,237 @@ - - - -PostgreSQL Developers FAQ - - -

Developer's Frequently Asked Questions (FAQ) for -PostgreSQL

-

Last updated: Wed Dec 1 16:11:11 EST 2006

+ + + -

Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
-

+ PostgreSQL Developers FAQ + -

The most recent version of this document can be viewed at http://www.PostgreSQL.org/docs/faqs/FAQ_DEV.html.

+ +

Developer's Frequently Asked Questions (FAQ) for + PostgreSQL

-
-
- -
-

General Questions

-
+

Last updated: Wed Dec 1 16:11:11 EST 2006

-1.1) How do I get involved in PostgreSQL -development?
- 1.2) What development environment is required -to develop code?
- 1.3) What areas need work?
- 1.4) What do I do after choosing an item to -work on?
- 1.5) Where can I learn more about the code?
- 1.6) I've developed a patch, what next?
- 1.7) How do I download/update the current -source tree?
- 1.8) How do I test my changes?
- 1.9) What tools are available for -developers?
- 1.10) What books are good for developers?
- 1.11) What is configure all about?
- 1.12) How do I add a new port?
- 1.13) Why don't you use threads/raw -devices/async-I/O, <insert your favorite wizz-bang feature -here>?
- 1.14) How are RPM's packaged?
- 1.15) How are CVS branches handled?
- 1.16) Where can I get a copy of the SQL -standards?
- 1.17) Where can I get technical -assistance?
- 1.18) How do I get involved in PostgreSQL web -site development?
- -
-

Technical Questions

-
+

Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
+

-2.1) How do I efficiently access information in -tables from the backend code?
- 2.2) Why are table, column, type, function, -view names sometimes referenced as Name or NameData, -and sometimes as char *?
- 2.3) Why do we use Node and List -to make data structures?
- 2.4) I just added a field to a structure. What -else should I do?
- 2.5) Why do we use palloc() and -pfree() to allocate memory?
- 2.6) What is ereport()?
- 2.7) What is CommandCounterIncrement()?
-
- -
-
-

General Questions

-
+

The most recent version of this document can be viewed at http://www.PostgreSQL.org/docs/faqs/FAQ_DEV.html.

+
+
+ -

1.1) How go I get involved in PostgreSQL -development?

+
+

General Questions

+
+ 1.1) How do I get involved in PostgreSQL + development?
+ 1.2) What development environment is required + to develop code?
+ 1.3) What areas need work?
+ 1.4) What do I do after choosing an item to + work on?
+ 1.5) Where can I learn more about the code?
+ 1.6) I've developed a patch, what next?
+ 1.7) How do I download/update the current + source tree?
+ 1.8) How do I test my changes?
+ 1.9) What tools are available for + developers?
+ 1.10) What books are good for developers?
+ 1.11) What is configure all about?
+ 1.12) How do I add a new port?
+ 1.13) Why don't you use threads/raw + devices/async-I/O, <insert your favorite wizz-bang feature + here>?
+ 1.14) How are RPM's packaged?
+ 1.15) How are CVS branches handled?
+ 1.16) Where can I get a copy of the SQL + standards?
+ 1.17) Where can I get technical + assistance?
+ 1.18) How do I get involved in PostgreSQL web + site development?
+ -

Download the code and have a look around. See 1.7.

+
+

Technical Questions

+
+ 2.1) How do I efficiently access information in + tables from the backend code?
+ 2.2) Why are table, column, type, function, + view names sometimes referenced as Name or NameData, + and sometimes as char *?
+ 2.3) Why do we use Node and List + to make data structures?
+ 2.4) I just added a field to a structure. What + else should I do?
+ 2.5) Why do we use palloc() and + pfree() to allocate memory?
+ 2.6) What is ereport()?
+ 2.7) What is CommandCounterIncrement()?
+
+ +
-

Subscribe to and read the pgsql-hackers -mailing list (often termed 'hackers'). This is where the major -contributors and core members of the project discuss -development.

+
+

General Questions

+
-

1.2) What development environment is required -to develop code?

+

1.1) How go I get involved in PostgreSQL + development?

-

PostgreSQL is developed mostly in the C programming language. It -also makes use of Yacc and Lex.

+

Download the code and have a look around. See 1.7.

-

The source code is targeted at most of the popular Unix -platforms and the Windows environment (XP, Windows 2000, and -up).

+

Subscribe to and read the pgsql-hackers + mailing list (often termed 'hackers'). This is where the major + contributors and core members of the project discuss + development.

-

Most developers make use of the open source development tool -chain. If you have contributed to open source software before, you -will probably be familiar with these tools. They include: GCC (http://gcc.gnu.org, GDB (www.gnu.org/software/gdb/gdb.html), -autoconf (www.gnu.org/software/autoconf/) -AND GNU make (www.gnu.org/software/make/make.html.

+

1.2) What development environment is required + to develop code?

-

Developers using this tool chain on Windows make use of MingW -(see http://www.mingw.org/).

+

PostgreSQL is developed mostly in the C programming language. It + also makes use of Yacc and Lex.

-

Some developers use compilers from other software vendors with -mixed results.

+

The source code is targeted at most of the popular Unix + platforms and the Windows environment (XP, Windows 2000, and + up).

-

Developers who are regularly rebuilding the source often pass -the --enable-depend flag to configure. The result is that -when you make a modification to a C header file, all files depend -upon that file are also rebuilt.

+

Most developers make use of the open source development tool + chain. If you have contributed to open source software before, you + will probably be familiar with these tools. They include: GCC (http://gcc.gnu.org, GDB (www.gnu.org/software/gdb/gdb.html), + autoconf (www.gnu.org/software/autoconf/) + AND GNU make (www.gnu.org/software/make/make.html.

-

1.3) What areas need work?

+

Developers using this tool chain on Windows make use of MingW + (see http://www.mingw.org/).

-Outstanding features are detailed in the TODO list. This is located -in doc/TODO in the source distribution or at http://developer.postgresql.org/todo.php. +

Some developers use compilers from other software vendors with + mixed results.

-

You can learn more about these features by consulting the -archives, the SQL standards and the recommend texts (see 1.10).

+

Developers who are regularly rebuilding the source often pass + the --enable-depend flag to configure. The result is that + when you make a modification to a C header file, all files depend + upon that file are also rebuilt.

-

1.4) What do I do after choosing an item to -work on?

+

1.3) What areas need work?

+ Outstanding features are detailed in the TODO list. This is located + in doc/TODO in the source distribution or at http://developer.postgresql.org/todo.php. + -

Send an email to pgsql-hackers with a proposal for what you want -to do (assuming your contribution is not trivial). Working in -isolation is not advisable: others may be working on the same TODO -item; you may have misunderstood the TODO item; your approach may -benefit from the review of others.

+

You can learn more about these features by consulting the + archives, the SQL standards and the recommend texts (see 1.10).

-

1.5) Where can I learn more about the -code?

+

1.4) What do I do after choosing an item to + work on?

-

Other than documentation in the source tree itself, you can find -some papers/presentations discussing the code at http://developers.postgresql.org.

+

Send an email to pgsql-hackers with a proposal for what you want + to do (assuming your contribution is not trivial). Working in + isolation is not advisable: others may be working on the same TODO + item; you may have misunderstood the TODO item; your approach may + benefit from the review of others.

-

1.6) I've developed a patch, what next?

+

1.5) Where can I learn more about the + code?

-

Generate the patch in contextual diff format. If you are -unfamiliar with this, you may find the script -src/tools/makediff/difforig useful.

+

Other than documentation in the source tree itself, you can find + some papers/presentations discussing the code at http://developers.postgresql.org.

-

Ensure that your patch is generated against the most recent -version of the code. If it is a patch adding new functionality, the -most recent version is cvs HEAD; if it is a bug fix, this will be -the most recently version of the branch which suffers from the bug -(for more on branches in PostgreSQL, see 1.15).

+

1.6) I've developed a patch, what next?

-

Finally, submit the patch to pgsql-patches@postgresql.org. It -will be reviewed by other contributors to the project and may be -either accepted or sent back for further work.

+

Generate the patch in contextual diff format. If you are + unfamiliar with this, you may find the script + src/tools/makediff/difforig useful.

-

1.7) How do I download/update the current -source tree?

+

Ensure that your patch is generated against the most recent + version of the code. If it is a patch adding new functionality, the + most recent version is cvs HEAD; if it is a bug fix, this will be + the most recently version of the branch which suffers from the bug + (for more on branches in PostgreSQL, see 1.15).

-

There are several ways to obtain the source tree. Occasional -developers can just get the most recent source tree snapshot from -ftp://ftp.postgresql.org.

+

Finally, submit the patch to pgsql-patches@postgresql.org. It + will be reviewed by other contributors to the project and may be + either accepted or sent back for further work.

-

Regular developers may want to take advantage of anonymous -access to our source code management system. The source tree is -currently hosted in CVS. For details of how to obtain the source -from CVS see http://developer.postgresql.org/docs/postgres/cvs.html.

+

1.7) How do I download/update the current + source tree?

-

1.8) How do I test my changes?

+

There are several ways to obtain the source tree. Occasional + developers can just get the most recent source tree snapshot from + ftp://ftp.postgresql.org.

-

Basic system testing

+

Regular developers may want to take advantage of anonymous + access to our source code management system. The source tree is + currently hosted in CVS. For details of how to obtain the source + from CVS see http://developer.postgresql.org/docs/postgres/cvs.html.

-

The easiest way to test your code is to ensure that it builds -against the latest verion of the code and that it does not generate -compiler warnings.

+

1.8) How do I test my changes?

-

It is worth advised that you pass --enable-cassert to -configure. This will turn on assertions with in the source -which will often show us bugs because they cause data corruption of -segmentation violations. This generally makes debugging much -easier.

+

Basic system testing

-

Then, perform run time testing via psql.

+

The easiest way to test your code is to ensure that it builds + against the latest verion of the code and that it does not generate + compiler warnings.

-

Regression test suite

+

It is worth advised that you pass --enable-cassert to + configure. This will turn on assertions with in the source + which will often show us bugs because they cause data corruption of + segmentation violations. This generally makes debugging much + easier.

-

The next step is to test your changes against the existing -regression test suite. To do this, issue "make check" in the root -directory of the source tree. If any tests failure, -investigate.

+

Then, perform run time testing via psql.

-

If you've deliberately changed existing behaviour, this change -may cause a regression test failure but not any actual regression. -If so, you should also patch the regression test suite.

+

Regression test suite

-

Other run time testing

+

The next step is to test your changes against the existing + regression test suite. To do this, issue "make check" in the root + directory of the source tree. If any tests failure, + investigate.

-

Some developers make use of tools such as valgrind (http://valgrind.kde.org) for memory -testing, gprof (which comes with the GNU binutils suite) and -oprofile (http://oprofile.sourceforge.net/) -for profiling and other related tools.

+

If you've deliberately changed existing behaviour, this change + may cause a regression test failure but not any actual regression. + If so, you should also patch the regression test suite.

-

What about unit testing, static analysis, model -checking...?

+

Other run time testing

-

There have been a number of discussions about other testing -frameworks and some developers are exploring these ideas.

+

Some developers make use of tools such as valgrind (http://valgrind.kde.org) for memory + testing, gprof (which comes with the GNU binutils suite) and + oprofile (http://oprofile.sourceforge.net/) + for profiling and other related tools.

-

1.9) What tools are available for -developers?

+

What about unit testing, static analysis, model + checking...?

-

First, all the files in the src/tools directory are -designed for developers.

+

There have been a number of discussions about other testing + frameworks and some developers are exploring these ideas.

-
+    
1.9) What tools are available for
+    developers?

+
+    
First, all the files in the src/tools directory are
+    designed for developers.

+
     RELEASE_CHANGES changes we have to make for each release
     backend         description/flowchart of the backend directories
     ccsym           find standard defines made by your compiler
@@ -251,54 +253,52 @@ designed for developers.

     pgindent        indents source files
     pgtest          a semi-automated build system
     thread          a thread testing script
-

+
-

In src/include/catalog:

- -
+    
In src/include/catalog:

+
     unused_oids     a script which generates unused OIDs for use in system
                      catalogs
     duplicate_oids  finds duplicate OIDs in system catalog definitions
-

+
+ If you point your browser at the tools/backend/index.html + file, you will see few paragraphs describing the data flow, the + backend components in a flow chart, and a description of the shared + memory area. You can click on any flowchart box to see a + description. If you then click on the directory name, you will be + taken to the source directory, to browse the actual source code + behind it. We also have several README files in some source + directories to describe the function of the module. The browser + will display these when you enter the directory also. The + tools/backend directory is also contained on our web page + under the title How PostgreSQL Processes a Query. -If you point your browser at the tools/backend/index.html -file, you will see few paragraphs describing the data flow, the -backend components in a flow chart, and a description of the shared -memory area. You can click on any flowchart box to see a -description. If you then click on the directory name, you will be -taken to the source directory, to browse the actual source code -behind it. We also have several README files in some source -directories to describe the function of the module. The browser -will display these when you enter the directory also. The -tools/backend directory is also contained on our web page -under the title How PostgreSQL Processes a Query. -

Second, you really should have an editor that can handle tags, -so you can tag a function call to see the function definition, and -then tag inside that function to see an even lower-level function, -and then back out twice to return to the original function. Most -editors support this via tags or etags files.

+

Second, you really should have an editor that can handle tags, + so you can tag a function call to see the function definition, and + then tag inside that function to see an even lower-level function, + and then back out twice to return to the original function. Most + editors support this via tags or etags files.

-

Third, you need to get id-utils from ftp://ftp.gnu.org/gnu/id-utils/

+

Third, you need to get id-utils from ftp://ftp.gnu.org/gnu/id-utils/

-

By running tools/make_mkid, an archive of source symbols -can be created that can be rapidly queried.

+

By running tools/make_mkid, an archive of source symbols + can be created that can be rapidly queried.

-

Some developers make use of cscope, which can be found at http://cscope.sf.net/. Others use -glimpse, which can be found at http://webglimpse.net/.

+

Some developers make use of cscope, which can be found at http://cscope.sf.net/. Others use + glimpse, which can be found at http://webglimpse.net/.

-

tools/make_diff has tools to create patch diff files that -can be applied to the distribution. This produces context diffs, -which is our preferred format.

+

tools/make_diff has tools to create patch diff files that + can be applied to the distribution. This produces context diffs, + which is our preferred format.

-

Our standard format is to indent each code level with one tab, -where each tab is four spaces. You will need to set your editor to -display tabs as four spaces:
-

- -
+    
Our standard format is to indent each code level with one tab,
+    where each tab is four spaces. You will need to set your editor to
+    display tabs as four spaces:

+    

+
     vi in ~/.exrc:
             set tabstop=4
             set sw=4
@@ -339,497 +339,492 @@ display tabs as four spaces:

              *  c-basic-offset: 4
              * End:
              */
-

+
+
+ pgindent will the format code by specifying flags to your + operating system's utility indent. This article + describes the value of a consistent coding style. -
- pgindent will the format code by specifying flags to your -operating system's utility indent. This article -describes the value of a consistent coding style. -

pgindent is run on all source files just before each beta -test period. It auto-formats all source files to make them -consistent. Comment blocks that need specific line breaks should be -formatted as block comments, where the comment starts as -/*------. These comments will not be reformatted in -any way.

+

pgindent is run on all source files just before each beta + test period. It auto-formats all source files to make them + consistent. Comment blocks that need specific line breaks should be + formatted as block comments, where the comment starts as + /*------. These comments will not be reformatted in + any way.

-

pginclude contains scripts used to add needed -#include's to include files, and removed unneeded -#include's.

+

pginclude contains scripts used to add needed + #include's to include files, and removed unneeded + #include's.

-

When adding system types, you will need to assign oids to them. -There is also a script called unused_oids in -pgsql/src/include/catalog that shows the unused oids.

+

When adding system types, you will need to assign oids to them. + There is also a script called unused_oids in + pgsql/src/include/catalog that shows the unused oids.

-

1.10) What books are good for -developers?

+

1.10) What books are good for + developers?

-

I have four good books, An Introduction to Database -Systems, by C.J. Date, Addison, Wesley, A Guide to the SQL -Standard, by C.J. Date, et. al, Addison, Wesley, -Fundamentals of Database Systems, by Elmasri and Navathe, -and Transaction Processing, by Jim Gray, Morgan, -Kaufmann

+

I have four good books, An Introduction to Database + Systems, by C.J. Date, Addison, Wesley, A Guide to the SQL + Standard, by C.J. Date, et. al, Addison, Wesley, + Fundamentals of Database Systems, by Elmasri and Navathe, + and Transaction Processing, by Jim Gray, Morgan, + Kaufmann

-

There is also a database performance site, with a handbook -on-line written by Jim Gray at http://www.benchmarkresources.com..

+

There is also a database performance site, with a handbook + on-line written by Jim Gray at http://www.benchmarkresources.com..

-

1.11) What is configure all about?

+

1.11) What is configure all about?

-

The files configure and configure.in are part of -the GNU autoconf package. Configure allows us to test for -various capabilities of the OS, and to set variables that can then -be tested in C programs and Makefiles. Autoconf is installed on the -PostgreSQL main server. To add options to configure, edit -configure.in, and then run autoconf to generate -configure.

+

The files configure and configure.in are part of + the GNU autoconf package. Configure allows us to test for + various capabilities of the OS, and to set variables that can then + be tested in C programs and Makefiles. Autoconf is installed on the + PostgreSQL main server. To add options to configure, edit + configure.in, and then run autoconf to generate + configure.

-

When configure is run by the user, it tests various OS -capabilities, stores those in config.status and -config.cache, and modifies a list of *.in files. For -example, if there exists a Makefile.in, configure generates -a Makefile that contains substitutions for all @var@ -parameters found by configure.

+

When configure is run by the user, it tests various OS + capabilities, stores those in config.status and + config.cache, and modifies a list of *.in files. For + example, if there exists a Makefile.in, configure generates + a Makefile that contains substitutions for all @var@ + parameters found by configure.

-

When you need to edit files, make sure you don't waste time -modifying files generated by configure. Edit the *.in -file, and re-run configure to recreate the needed file. If -you run make distclean from the top-level source directory, -all files derived by configure are removed, so you see only the -file contained in the source distribution.

+

When you need to edit files, make sure you don't waste time + modifying files generated by configure. Edit the *.in + file, and re-run configure to recreate the needed file. If + you run make distclean from the top-level source directory, + all files derived by configure are removed, so you see only the + file contained in the source distribution.

-

1.12) How do I add a new port?

+

1.12) How do I add a new port?

-

There are a variety of places that need to be modified to add a -new port. First, start in the src/template directory. Add an -appropriate entry for your OS. Also, use src/config.guess to -add your OS to src/template/.similar. You shouldn't match -the OS version exactly. The configure test will look for an -exact OS version number, and if not found, find a match without -version number. Edit src/configure.in to add your new OS. -(See configure item above.) You will need to run autoconf, or patch -src/configure too.

+

There are a variety of places that need to be modified to add a + new port. First, start in the src/template directory. Add an + appropriate entry for your OS. Also, use src/config.guess to + add your OS to src/template/.similar. You shouldn't match + the OS version exactly. The configure test will look for an + exact OS version number, and if not found, find a match without + version number. Edit src/configure.in to add your new OS. + (See configure item above.) You will need to run autoconf, or patch + src/configure too.

-

Then, check src/include/port and add your new OS file, -with appropriate values. Hopefully, there is already locking code -in src/include/storage/s_lock.h for your CPU. There is also -a src/makefiles directory for port-specific Makefile -handling. There is a backend/port directory if you need -special files for your OS.

+

Then, check src/include/port and add your new OS file, + with appropriate values. Hopefully, there is already locking code + in src/include/storage/s_lock.h for your CPU. There is also + a src/makefiles directory for port-specific Makefile + handling. There is a backend/port directory if you need + special files for your OS.

-

1.13) Why don't you use threads/raw -devices/async-I/O, <insert your favorite wizz-bang feature -here>?

+

1.13) Why don't you use threads/raw + devices/async-I/O, <insert your favorite wizz-bang feature + here>?

-

There is always a temptation to use the newest operating system -features as soon as they arrive. We resist that temptation.

+

There is always a temptation to use the newest operating system + features as soon as they arrive. We resist that temptation.

-

First, we support 15+ operating systems, so any new feature has -to be well established before we will consider it. Second, most new -wizz-bang features don't provide dramatic -improvements. Third, they usually have some downside, such as -decreased reliability or additional code required. Therefore, we -don't rush to use new features but rather wait for the feature to -be established, then ask for testing to show that a measurable -improvement is possible.

+

First, we support 15+ operating systems, so any new feature has + to be well established before we will consider it. Second, most new + wizz-bang features don't provide dramatic + improvements. Third, they usually have some downside, such as + decreased reliability or additional code required. Therefore, we + don't rush to use new features but rather wait for the feature to + be established, then ask for testing to show that a measurable + improvement is possible.

-

As an example, threads are not currently used in the backend -code because:

+

As an example, threads are not currently used in the backend + code because:

- -

So, we are not ignorant of new features. It is just that we are -cautious about their adoption. The TODO list often contains links -to discussions showing our reasoning in these areas.

+

So, we are not ignorant of new features. It is just that we are + cautious about their adoption. The TODO list often contains links + to discussions showing our reasoning in these areas.

-

1.14) How are RPMs packaged?

+

1.14) How are RPMs packaged?

-

This was written by Lamar Owen:

+

This was written by Lamar Owen:

-

2001-05-03

+

2001-05-03

-

As to how the RPMs are built -- to answer that question sanely -requires me to know how much experience you have with the whole RPM -paradigm. 'How is the RPM built?' is a multifaceted question. The -obvious simple answer is that I maintain:

+

As to how the RPMs are built -- to answer that question sanely + requires me to know how much experience you have with the whole RPM + paradigm. 'How is the RPM built?' is a multifaceted question. The + obvious simple answer is that I maintain:

-
    -
  1. A set of patches to make certain portions of the source tree -'behave' in the different environment of the RPMset;
    2. +
      +
    1. A set of patches to make certain portions of the source tree + 'behave' in the different environment of the RPMset;
      2. -
    2. The initscript;
      3. +
    3. The initscript;
      4. -
    4. Any other ancilliary scripts and files;
      5. +
    5. Any other ancilliary scripts and files;
      6. -
    6. A README.rpm-dist document that tries to adequately document -both the differences between the RPM build and the WHY of the -differences, as well as useful RPM environment operations (like, -using syslog, upgrading, getting postmaster to start at OS boot, -etc);
      7. +
    7. A README.rpm-dist document that tries to adequately document + both the differences between the RPM build and the WHY of the + differences, as well as useful RPM environment operations (like, + using syslog, upgrading, getting postmaster to start at OS boot, + etc);
      8. -
    8. The spec file that throws it all together. This is not a -trivial undertaking in a package of this size.
      9. -
    +
  2. The spec file that throws it all together. This is not a + trivial undertaking in a package of this size.
    3. +
-

I then download and build on as many different canonical -distributions as I can -- currently I am able to build on Red Hat -6.2, 7.0, and 7.1 on my personal hardware. Occasionally I receive -opportunity from certain commercial enterprises such as Great -Bridge and PostgreSQL, Inc. to build on other distributions.

+

I then download and build on as many different canonical + distributions as I can -- currently I am able to build on Red Hat + 6.2, 7.0, and 7.1 on my personal hardware. Occasionally I receive + opportunity from certain commercial enterprises such as Great + Bridge and PostgreSQL, Inc. to build on other distributions.

-

I test the build by installing the resulting packages and -running the regression tests. Once the build passes these tests, I -upload to the postgresql.org ftp server and make a release -announcement. I am also responsible for maintaining the RPM -download area on the ftp site.

+

I test the build by installing the resulting packages and + running the regression tests. Once the build passes these tests, I + upload to the postgresql.org ftp server and make a release + announcement. I am also responsible for maintaining the RPM + download area on the ftp site.

-

You'll notice I said 'canonical' distributions above. That -simply means that the machine is as stock 'out of the box' as -practical -- that is, everything (except select few programs) on -these boxen are installed by RPM; only official Red Hat released -RPMs are used (except in unusual circumstances involving software -that will not alter the build -- for example, installing a newer -non-RedHat version of the Dia diagramming package is OK -- -installing Python 2.1 on the box that has Python 1.5.2 installed is -not, as that alters the PostgreSQL build). The RPM as uploaded is -built to as close to out-of-the-box pristine as is possible. Only -the standard released 'official to that release' compiler is used --- and only the standard official kernel is used as well.

+

You'll notice I said 'canonical' distributions above. That + simply means that the machine is as stock 'out of the box' as + practical -- that is, everything (except select few programs) on + these boxen are installed by RPM; only official Red Hat released + RPMs are used (except in unusual circumstances involving software + that will not alter the build -- for example, installing a newer + non-RedHat version of the Dia diagramming package is OK -- + installing Python 2.1 on the box that has Python 1.5.2 installed is + not, as that alters the PostgreSQL build). The RPM as uploaded is + built to as close to out-of-the-box pristine as is possible. Only + the standard released 'official to that release' compiler is used + -- and only the standard official kernel is used as well.

-

For a time I built on Mandrake for RedHat consumption -- no -more. Nonstandard RPM building systems are worse than useless. -Which is not to say that Mandrake is useless! By no means is -Mandrake useless -- unless you are building Red Hat RPMs -- and Red -Hat is useless if you're trying to build Mandrake or SuSE RPMs, for -that matter. But I would be foolish to use 'Lamar Owen's Super -Special RPM Blend Distro 0.1.2' to build for public consumption! -:-)

+

For a time I built on Mandrake for RedHat consumption -- no + more. Nonstandard RPM building systems are worse than useless. + Which is not to say that Mandrake is useless! By no means is + Mandrake useless -- unless you are building Red Hat RPMs -- and Red + Hat is useless if you're trying to build Mandrake or SuSE RPMs, for + that matter. But I would be foolish to use 'Lamar Owen's Super + Special RPM Blend Distro 0.1.2' to build for public consumption! + :-)

-

I _do_ attempt to make the _source_ RPM compatible with as many -distributions as possible -- however, since I have limited -resources (as a volunteer RPM maintainer) I am limited as to the -amount of testing said build will get on other distributions, -architectures, or systems.

+

I _do_ attempt to make the _source_ RPM compatible with as many + distributions as possible -- however, since I have limited + resources (as a volunteer RPM maintainer) I am limited as to the + amount of testing said build will get on other distributions, + architectures, or systems.

-

And, while I understand people's desire to immediately upgrade -to the newest version, realize that I do this as a side interest -- -I have a regular, full-time job as a broadcast -engineer/webmaster/sysadmin/Technical Director which occasionally -prevents me from making timely RPM releases. This happened during -the early part of the 7.1 beta cycle -- but I believe I was pretty -much on the ball for the Release Candidates and the final -release.

+

And, while I understand people's desire to immediately upgrade + to the newest version, realize that I do this as a side interest -- + I have a regular, full-time job as a broadcast + engineer/webmaster/sysadmin/Technical Director which occasionally + prevents me from making timely RPM releases. This happened during + the early part of the 7.1 beta cycle -- but I believe I was pretty + much on the ball for the Release Candidates and the final + release.

-

I am working towards a more open RPM distribution -- I would -dearly love to more fully document the process and put everything -into CVS -- once I figure out how I want to represent things such -as the spec file in a CVS form. It makes no sense to maintain a -changelog, for instance, in the spec file in CVS when CVS does a -better job of changelogs -- I will need to write a tool to generate -a real spec file from a CVS spec-source file that would add version -numbers, changelog entries, etc to the result before building the -RPM. IOW, I need to rethink the process -- and then go through the -motions of putting my long RPM history into CVS one version at a -time so that version history information isn't lost.

+

I am working towards a more open RPM distribution -- I would + dearly love to more fully document the process and put everything + into CVS -- once I figure out how I want to represent things such + as the spec file in a CVS form. It makes no sense to maintain a + changelog, for instance, in the spec file in CVS when CVS does a + better job of changelogs -- I will need to write a tool to generate + a real spec file from a CVS spec-source file that would add version + numbers, changelog entries, etc to the result before building the + RPM. IOW, I need to rethink the process -- and then go through the + motions of putting my long RPM history into CVS one version at a + time so that version history information isn't lost.

-

As to why all these files aren't part of the source tree, well, -unless there was a large cry for it to happen, I don't believe it -should. PostgreSQL is very platform-agnostic -- and I like that. -Including the RPM stuff as part of the Official Tarball (TM) would, -IMHO, slant that agnostic stance in a negative way. But maybe I'm -too sensitive to that. I'm not opposed to doing that if that is the -consensus of the core group -- and that would be a sneaky way to -get the stuff into CVS :-). But if the core group isn't thrilled -with the idea (and my instinct says they're not likely to be), I am -opposed to the idea -- not to keep the stuff to myself, but to not -hinder the platform-neutral stance. IMHO, of course.

+

As to why all these files aren't part of the source tree, well, + unless there was a large cry for it to happen, I don't believe it + should. PostgreSQL is very platform-agnostic -- and I like that. + Including the RPM stuff as part of the Official Tarball (TM) would, + IMHO, slant that agnostic stance in a negative way. But maybe I'm + too sensitive to that. I'm not opposed to doing that if that is the + consensus of the core group -- and that would be a sneaky way to + get the stuff into CVS :-). But if the core group isn't thrilled + with the idea (and my instinct says they're not likely to be), I am + opposed to the idea -- not to keep the stuff to myself, but to not + hinder the platform-neutral stance. IMHO, of course.

-

Of course, there are many projects that DO include all the files -necessary to build RPMs from their Official Tarball (TM).

+

Of course, there are many projects that DO include all the files + necessary to build RPMs from their Official Tarball (TM).

-

1.15) How are CVS branches managed?

+

1.15) How are CVS branches managed?

-

This was written by Tom Lane:

+

This was written by Tom Lane:

-

2001-05-07

+

2001-05-07

-

If you just do basic "cvs checkout", "cvs update", "cvs commit", -then you'll always be dealing with the HEAD version of the files in -CVS. That's what you want for development, but if you need to patch -past stable releases then you have to be able to access and update -the "branch" portions of our CVS repository. We normally fork off a -branch for a stable release just before starting the development -cycle for the next release.

+

If you just do basic "cvs checkout", "cvs update", "cvs commit", + then you'll always be dealing with the HEAD version of the files in + CVS. That's what you want for development, but if you need to patch + past stable releases then you have to be able to access and update + the "branch" portions of our CVS repository. We normally fork off a + branch for a stable release just before starting the development + cycle for the next release.

-

The first thing you have to know is the branch name for the -branch you are interested in getting at. To do this, look at some -long-lived file, say the top-level HISTORY file, with "cvs status --v" to see what the branch names are. (Thanks to Ian Lance Taylor -for pointing out that this is the easiest way to do it.) Typical -branch names are:

- -
+    
The first thing you have to know is the branch name for the
+    branch you are interested in getting at. To do this, look at some
+    long-lived file, say the top-level HISTORY file, with "cvs status
+    -v" to see what the branch names are. (Thanks to Ian Lance Taylor
+    for pointing out that this is the easiest way to do it.) Typical
+    branch names are:

+
     REL7_1_STABLE
     REL7_0_PATCHES
     REL6_5_PATCHES
-

+
-

OK, so how do you do work on a branch? By far the best way is to -create a separate checkout tree for the branch and do your work in -that. Not only is that the easiest way to deal with CVS, but you -really need to have the whole past tree available anyway to test -your work. (And you *better* test your work. Never forget that -dot-releases tend to go out with very little beta testing --- so -whenever you commit an update to a stable branch, you'd better be -doubly sure that it's correct.)

+

OK, so how do you do work on a branch? By far the best way is to + create a separate checkout tree for the branch and do your work in + that. Not only is that the easiest way to deal with CVS, but you + really need to have the whole past tree available anyway to test + your work. (And you *better* test your work. Never forget that + dot-releases tend to go out with very little beta testing --- so + whenever you commit an update to a stable branch, you'd better be + doubly sure that it's correct.)

-

Normally, to checkout the head branch, you just cd to the place -you want to contain the toplevel "pgsql" directory and say

- -
+    
Normally, to checkout the head branch, you just cd to the place
+    you want to contain the toplevel "pgsql" directory and say

+
     cvs ... checkout pgsql
-

+
-

To get a past branch, you cd to whereever you want it and -say

- -
+    
To get a past branch, you cd to whereever you want it and
+    say

+
     cvs ... checkout -r BRANCHNAME pgsql
-

+
-

For example, just a couple days ago I did

- -
+    
For example, just a couple days ago I did

+
     mkdir ~postgres/REL7_1
     cd ~postgres/REL7_1
     cvs ... checkout -r REL7_1_STABLE pgsql
-

+
-

and now I have a maintenance copy of 7.1.*.

+

and now I have a maintenance copy of 7.1.*.

-

When you've done a checkout in this way, the branch name is -"sticky": CVS automatically knows that this directory tree is for -the branch, and whenever you do "cvs update" or "cvs commit" in -this tree, you'll fetch or store the latest version in the branch, -not the head version. Easy as can be.

+

When you've done a checkout in this way, the branch name is + "sticky": CVS automatically knows that this directory tree is for + the branch, and whenever you do "cvs update" or "cvs commit" in + this tree, you'll fetch or store the latest version in the branch, + not the head version. Easy as can be.

-

So, if you have a patch that needs to apply to both the head and -a recent stable branch, you have to make the edits and do the -commit twice, once in your development tree and once in your stable -branch tree. This is kind of a pain, which is why we don't normally -fork the tree right away after a major release --- we wait for a -dot-release or two, so that we won't have to double-patch the first -wave of fixes.

+

So, if you have a patch that needs to apply to both the head and + a recent stable branch, you have to make the edits and do the + commit twice, once in your development tree and once in your stable + branch tree. This is kind of a pain, which is why we don't normally + fork the tree right away after a major release --- we wait for a + dot-release or two, so that we won't have to double-patch the first + wave of fixes.

-

1.16) Where can I get a copy of the SQL -standards?

+

1.16) Where can I get a copy of the SQL + standards?

-

There are three versions of the SQL standard: SQL-92, SQL:1999, -and SQL:2003. They are endorsed by ANSI and ISO. Draft versions can -be downloaded from:

+

There are three versions of the SQL standard: SQL-92, SQL:1999, + and SQL:2003. They are endorsed by ANSI and ISO. Draft versions can + be downloaded from:

- -

Some SQL standards web pages are:

+

Some SQL standards web pages are:

- -

1.17) Where can I get technical -assistance?

+

1.17) Where can I get technical + assistance?

-

Many technical questions held by those new to the code have been -answered on the pgsql-hackers mailing list - the archives of which -can be found at http://archives.postgresql.org/pgsql-hackers/.

+

Many technical questions held by those new to the code have been + answered on the pgsql-hackers mailing list - the archives of which + can be found at http://archives.postgresql.org/pgsql-hackers/.

-

If you cannot find discussion or your particular question, feel -free to put it to the list.

+

If you cannot find discussion or your particular question, feel + free to put it to the list.

-

Major contributors also answer technical questions, including -questions about development of new features, on IRC at -irc.freenode.net in the #postgresql channel.

+

Major contributors also answer technical questions, including + questions about development of new features, on IRC at + irc.freenode.net in the #postgresql channel.

-

1.18) How go I get involved in PostgreSQL -web site development?

+

1.18) How go I get involved in PostgreSQL + web site development?

-

PostgreSQL website development is discussed on the -pgsql-www@postgresql.org mailing list. The is a project page where -the source code is available at http://gborg.postgresql.org/project/pgweb/projdisplay.php -, the code for the next version of the website is under the -"portal" module. You will al so find code for the "techdocs" -website if you would like to contribute to that. A temporary todo -list for current website development issues is available at http://xzilla.postgresql.org/todo

+

PostgreSQL website development is discussed on the + pgsql-www@postgresql.org mailing list. The is a project page where + the source code is available at http://gborg.postgresql.org/project/pgweb/projdisplay.php + , the code for the next version of the website is under the + "portal" module. You will al so find code for the "techdocs" + website if you would like to contribute to that. A temporary todo + list for current website development issues is available at http://xzilla.postgresql.org/todo

-
-

Technical Questions

-
+
+

Technical Questions

+
-

2.1) How do I efficiently access information -in tables from the backend code?

+

2.1) How do I efficiently access information + in tables from the backend code?

-

You first need to find the tuples(rows) you are interested in. -There are two ways. First, SearchSysCache() and related -functions allow you to query the system catalogs. This is the -preferred way to access system tables, because the first call to -the cache loads the needed rows, and future requests can return the -results without accessing the base table. The caches use system -table indexes to look up tuples. A list of available caches is -located in src/backend/utils/cache/syscache.c. -src/backend/utils/cache/lsyscache.c contains many -column-specific cache lookup functions.

+

You first need to find the tuples(rows) you are interested in. + There are two ways. First, SearchSysCache() and related + functions allow you to query the system catalogs. This is the + preferred way to access system tables, because the first call to + the cache loads the needed rows, and future requests can return the + results without accessing the base table. The caches use system + table indexes to look up tuples. A list of available caches is + located in src/backend/utils/cache/syscache.c. + src/backend/utils/cache/lsyscache.c contains many + column-specific cache lookup functions.

-

The rows returned are cache-owned versions of the heap rows. -Therefore, you must not modify or delete the tuple returned by -SearchSysCache(). What you should do is release it -with ReleaseSysCache() when you are done using it; this -informs the cache that it can discard that tuple if necessary. If -you neglect to call ReleaseSysCache(), then the cache entry -will remain locked in the cache until end of transaction, which is -tolerable but not very desirable.

+

The rows returned are cache-owned versions of the heap rows. + Therefore, you must not modify or delete the tuple returned by + SearchSysCache(). What you should do is release it + with ReleaseSysCache() when you are done using it; this + informs the cache that it can discard that tuple if necessary. If + you neglect to call ReleaseSysCache(), then the cache entry + will remain locked in the cache until end of transaction, which is + tolerable but not very desirable.

-

If you can't use the system cache, you will need to retrieve the -data directly from the heap table, using the buffer cache that is -shared by all backends. The backend automatically takes care of -loading the rows into the buffer cache.

+

If you can't use the system cache, you will need to retrieve the + data directly from the heap table, using the buffer cache that is + shared by all backends. The backend automatically takes care of + loading the rows into the buffer cache.

-

Open the table with heap_open(). You can then start a -table scan with heap_beginscan(), then use -heap_getnext() and continue as long as -HeapTupleIsValid() returns true. Then do a -heap_endscan(). Keys can be assigned to the -scan. No indexes are used, so all rows are going to be -compared to the keys, and only the valid rows returned.

+

Open the table with heap_open(). You can then start a + table scan with heap_beginscan(), then use + heap_getnext() and continue as long as + HeapTupleIsValid() returns true. Then do a + heap_endscan(). Keys can be assigned to the + scan. No indexes are used, so all rows are going to be + compared to the keys, and only the valid rows returned.

-

You can also use heap_fetch() to fetch rows by block -number/offset. While scans automatically lock/unlock rows from the -buffer cache, with heap_fetch(), you must pass a -Buffer pointer, and ReleaseBuffer() it when -completed.

+

You can also use heap_fetch() to fetch rows by block + number/offset. While scans automatically lock/unlock rows from the + buffer cache, with heap_fetch(), you must pass a + Buffer pointer, and ReleaseBuffer() it when + completed.

-

Once you have the row, you can get data that is common to all -tuples, like t_self and t_oid, by merely accessing -the HeapTuple structure entries. If you need a -table-specific column, you should take the HeapTuple pointer, and -use the GETSTRUCT() macro to access the table-specific start -of the tuple. You then cast the pointer as a Form_pg_proc -pointer if you are accessing the pg_proc table, or -Form_pg_type if you are accessing pg_type. You can then -access the columns by using a structure pointer:

+

Once you have the row, you can get data that is common to all + tuples, like t_self and t_oid, by merely accessing + the HeapTuple structure entries. If you need a + table-specific column, you should take the HeapTuple pointer, and + use the GETSTRUCT() macro to access the table-specific start + of the tuple. You then cast the pointer as a Form_pg_proc + pointer if you are accessing the pg_proc table, or + Form_pg_type if you are accessing pg_type. You can then + access the columns by using a structure pointer:

+
+((Form_pg_class) GETSTRUCT(tuple))->relnatts
+
+
+ You must not directly change live tuples in this way. The + best way is to use heap_modifytuple() and pass it your + original tuple, and the values you want changed. It returns a + palloc'ed tuple, which you pass to heap_replace(). You can + delete tuples by passing the tuple's t_self to + heap_destroy(). You use t_self for + heap_update() too. Remember, tuples can be either system + cache copies, which may go away after you call + ReleaseSysCache(), or read directly from disk buffers, which + go away when you heap_getnext(), heap_endscan, or + ReleaseBuffer(), in the heap_fetch() case. Or it may + be a palloc'ed tuple, that you must pfree() when finished. -
-((Form_pg_class) GETSTRUCT(tuple))->relnatts
-
-
+

2.2) Why are table, column, type, function, + view names sometimes referenced as Name or NameData, + and sometimes as char *?

-You must not directly change live tuples in this way. The -best way is to use heap_modifytuple() and pass it your -original tuple, and the values you want changed. It returns a -palloc'ed tuple, which you pass to heap_replace(). You can -delete tuples by passing the tuple's t_self to -heap_destroy(). You use t_self for -heap_update() too. Remember, tuples can be either system -cache copies, which may go away after you call -ReleaseSysCache(), or read directly from disk buffers, which -go away when you heap_getnext(), heap_endscan, or -ReleaseBuffer(), in the heap_fetch() case. Or it may -be a palloc'ed tuple, that you must pfree() when finished. -

2.2) Why are table, column, type, function, -view names sometimes referenced as Name or NameData, -and sometimes as char *?

- -

Table, column, type, function, and view names are stored in -system tables in columns of type Name. Name is a -fixed-length, null-terminated type of NAMEDATALEN bytes. -(The default value for NAMEDATALEN is 64 bytes.)

- -
-typedef struct nameData
+    
Table, column, type, function, and view names are stored in
+    system tables in columns of type Name. Name is a
+    fixed-length, null-terminated type of NAMEDATALEN bytes.
+    (The default value for NAMEDATALEN is 64 bytes.)

+
+typedef struct nameData
     {
         char        data[NAMEDATALEN];
     } NameData;
     typedef NameData *Name;
-
-

+
+
+ Table, column, type, function, and view names that come into the + backend via user queries are stored as variable-length, + null-terminated character strings. -Table, column, type, function, and view names that come into the -backend via user queries are stored as variable-length, -null-terminated character strings. -

Many functions are called with both types of names, ie. -heap_open(). Because the Name type is null-terminated, it is -safe to pass it to a function expecting a char *. Because there are -many cases where on-disk names(Name) are compared to user-supplied -names(char *), there are many cases where Name and char * are used -interchangeably.

+

Many functions are called with both types of names, ie. + heap_open(). Because the Name type is null-terminated, it is + safe to pass it to a function expecting a char *. Because there are + many cases where on-disk names(Name) are compared to user-supplied + names(char *), there are many cases where Name and char * are used + interchangeably.

-

2.3) Why do we use Node and -List to make data structures?

+

2.3) Why do we use Node and + List to make data structures?

-

We do this because this allows a consistent way to pass data -inside the backend in a flexible way. Every node has a -NodeTag which specifies what type of data is inside the -Node. Lists are groups of Nodes chained together as a -forward-linked list.

+

We do this because this allows a consistent way to pass data + inside the backend in a flexible way. Every node has a + NodeTag which specifies what type of data is inside the + Node. Lists are groups of Nodes chained together as a + forward-linked list.

-

Here are some of the List manipulation commands:

+

Here are some of the List manipulation commands:

-
-
-
lfirst(i), lfirst_int(i), lfirst_oid(i)
+
+
+
lfirst(i), lfirst_int(i), lfirst_oid(i)
-
return the data (a point, inteter and OID respectively) at list -element i.
+
return the data (a point, inteter and OID respectively) at + list element i.
-
lnext(i)
+
lnext(i)
-
return the next list element after i.
+
return the next list element after i.
-
foreach(i, list)
+
foreach(i, list)
-
loop through list, assigning each list element to -i. It is important to note that i is a List *, not -the data in the List element. You need to use -lfirst(i) to get at the data. Here is a typical code snippet -that loops through a List containing Var *'s and processes -each one: -
-   List                *list;
+        

+          loop through list, assigning each list element to
+          i. It is important to note that i is a List *,
+          not the data in the List element. You need to use
+          lfirst(i) to get at the data. Here is a typical code
+          snippet that loops through a List containing Var *'s
+          and processes each one: 
+
+ List                *list;
     ListCell    *i;
     
     foreach(i, list)
@@ -838,114 +833,112 @@ each one:
 
         /* process var here */
     }
-
-

-

+
+
+
-
lcons(node, list)
+
lcons(node, list)
-
add node to the front of list, or create a new -list with node if list is NIL.
+
add node to the front of list, or create a + new list with node if list is NIL.
-
lappend(list, node)
+
lappend(list, node)
-
add node to the end of list. This is more -expensive that lcons.
+
add node to the end of list. This is more + expensive that lcons.
-
nconc(list1, list2)
+
nconc(list1, list2)
-
Concat list2 on to the end of list1.
+
Concat list2 on to the end of list1.
-
length(list)
+
length(list)
-
return the length of the list.
+
return the length of the list.
-
nth(i, list)
+
nth(i, list)
-
return the i'th element in list.
+
return the i'th element in list.
-
lconsi, ...
+
lconsi, ...
-
There are integer versions of these: lconsi, lappendi, -etc. Also versions for OID lists: lconso, lappendo, -etc.
-
-
- -You can print nodes easily inside gdb. First, to disable -output truncation when you use the gdb print command: -
-(gdb) set print elements 0
-
-
- -Instead of printing values in gdb format, you can use the next two -commands to print out List, Node, and structure contents in a -verbose format that is easier to understand. List's are unrolled -into nodes, and nodes are printed in detail. The first prints in a -short format, and the second in a long format: -
-(gdb) call print(any_pointer)
+        
There are integer versions of these: lconsi,
+        lappendi, etc. Also versions for OID lists: lconso,
+        lappendo, etc.

+
+
+ You can print nodes easily inside gdb. First, to disable + output truncation when you use the gdb print command: +
+(gdb) set print elements 0
+
+
+ Instead of printing values in gdb format, you can use the next two + commands to print out List, Node, and structure contents in a + verbose format that is easier to understand. List's are unrolled + into nodes, and nodes are printed in detail. The first prints in a + short format, and the second in a long format: +
+(gdb) call print(any_pointer)
     (gdb) call pprint(any_pointer)
-
-
+ + + The output appears in the postmaster log file, or on your screen if + you are running a backend directly without a postmaster. -The output appears in the postmaster log file, or on your screen if -you are running a backend directly without a postmaster. -

2.4) I just added a field to a structure. -What else should I do?

+

2.4) I just added a field to a structure. + What else should I do?

-

The structures passing around from the parser, rewrite, -optimizer, and executor require quite a bit of support. Most -structures have support routines in src/backend/nodes used -to create, copy, read, and output those structures (in particular, -the files copyfuncs.c and equalfuncs.c. Make sure you -add support for your new field to these files. Find any other -places the structure may need code for your new field. mkid -is helpful with this (see 1.9).

+

The structures passing around from the parser, rewrite, + optimizer, and executor require quite a bit of support. Most + structures have support routines in src/backend/nodes used + to create, copy, read, and output those structures (in particular, + the files copyfuncs.c and equalfuncs.c. Make sure you + add support for your new field to these files. Find any other + places the structure may need code for your new field. mkid + is helpful with this (see 1.9).

-

2.5) Why do we use palloc() and -pfree() to allocate memory?

+

2.5) Why do we use palloc() and + pfree() to allocate memory?

-

palloc() and pfree() are used in place of malloc() -and free() because we find it easier to automatically free all -memory allocated when a query completes. This assures us that all -memory that was allocated gets freed even if we have lost track of -where we allocated it. There are special non-query contexts that -memory can be allocated in. These affect when the allocated memory -is freed by the backend.

+

palloc() and pfree() are used in place of malloc() + and free() because we find it easier to automatically free all + memory allocated when a query completes. This assures us that all + memory that was allocated gets freed even if we have lost track of + where we allocated it. There are special non-query contexts that + memory can be allocated in. These affect when the allocated memory + is freed by the backend.

-

2.6) What is ereport()?

+

2.6) What is ereport()?

-

ereport() is used to send messages to the front-end, and -optionally terminate the current query being processed. The first -parameter is an ereport level of DEBUG (levels 1-5), -LOG, INFO, NOTICE, ERROR, FATAL, -or PANIC. NOTICE prints on the user's terminal and -the postmaster logs. INFO prints only to the user's terminal -and LOG prints only to the server logs. (These can be -changed from postgresql.conf.) ERROR prints in both -places, and terminates the current query, never returning from the -call. FATAL terminates the backend process. The remaining -parameters of ereport are a printf-style set of -parameters to print.

+

ereport() is used to send messages to the front-end, and + optionally terminate the current query being processed. The first + parameter is an ereport level of DEBUG (levels 1-5), + LOG, INFO, NOTICE, ERROR, FATAL, + or PANIC. NOTICE prints on the user's terminal and + the postmaster logs. INFO prints only to the user's terminal + and LOG prints only to the server logs. (These can be + changed from postgresql.conf.) ERROR prints in both + places, and terminates the current query, never returning from the + call. FATAL terminates the backend process. The remaining + parameters of ereport are a printf-style set of + parameters to print.

-

ereport(ERROR) frees most memory and open file -descriptors so you don't need to clean these up before the -call.

+

ereport(ERROR) frees most memory and open file + descriptors so you don't need to clean these up before the + call.

-

2.7) What is CommandCounterIncrement()?

+

2.7) What is CommandCounterIncrement()?

-

Normally, transactions can not see the rows they modify. This -allows UPDATE foo SET x = x + 1 to work correctly.

+

Normally, transactions can not see the rows they modify. This + allows UPDATE foo SET x = x + 1 to work correctly.

-

However, there are cases where a transactions needs to see rows -affected in previous parts of the transaction. This is accomplished -using a Command Counter. Incrementing the counter allows -transactions to be broken into pieces so each piece can see rows -modified by previous pieces. CommandCounterIncrement() -increments the Command Counter, creating a new part of the -transaction.

- - +

However, there are cases where a transactions needs to see rows + affected in previous parts of the transaction. This is accomplished + using a Command Counter. Incrementing the counter allows + transactions to be broken into pieces so each piece can see rows + modified by previous pieces. CommandCounterIncrement() + increments the Command Counter, creating a new part of the + transaction.

+ +