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Bruce Momjian
28 years ago
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Developer's Frequently Asked Questions (FAQ) for PostgreSQL |
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Last updated: Wed Feb 11 20:23:01 EST 1998 |
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Current maintainer: Bruce Momjian (maillist@candle.pha.pa.us) |
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The most recent version of this document can be viewed at the postgreSQL Web |
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site, http://postgreSQL.org. |
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------------------------------------------------------------------------ |
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Questions answered: |
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1) What tools are available for developers? |
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2) What books are good for developers? |
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3) Why do we use palloc() and pfree() to allocate memory? |
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4) Why do we use Node and List to make data structures? |
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5) How do I add a feature or fix a bug? |
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6) How do I download/update the current source tree? |
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7) How do I test my changes? |
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------------------------------------------------------------------------ |
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1) What tools are available for developers? |
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Aside from the User documentation mentioned in the regular FAQ, there are |
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several development tools available. First, all the files in the /tools |
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directory are designed for developers. |
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RELEASE_CHANGES changes we have to make for each release |
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SQL_keywords standard SQL'92 keywords |
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backend web flowchart of the backend directories |
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ccsym find standard defines made by your compiler |
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entab converts tabs to spaces, used by pgindent |
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find_static finds functions that could be made static |
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find_typedef get a list of typedefs in the source code |
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make_ctags make vi 'tags' file in each directory |
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make_diff make *.orig and diffs of source |
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make_etags make emacs 'etags' files |
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make_keywords.README make comparison of our keywords and SQL'92 |
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make_mkid make mkid ID files |
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mkldexport create AIX exports file |
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pgindent indents C source files |
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Let me note some of these. If you point your browser at the tools/backend |
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directory, you will see all the backend components in a flow chart. You can |
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click on any one to see a description. If you then click on the directory |
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name, you will be taken to the source directory, to browse the actual source |
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code behind it. We also have several README files in some source directories |
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to describe the function of the module. The browser will display these when |
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you enter the directory also. The tools/backend directory is also contained |
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on our web page under the title Backend Flowchart. |
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Second, you really should have an editor that can handle tags, so you can |
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tag a function call to see the function definition, and then tag inside that |
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function to see an even lower-level function, and then back out twice to |
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return to the original function. Most editors support this via tags or etags |
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files. |
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Third, you need to get mkid from ftp.postgresql.org. By running |
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tools/make_mkid, an archive of source symbols can be created that can be |
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rapidly queried like grep or edited. |
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make_diff has tools to create patch diff files that can be applied to the |
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distribution. |
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pgindent will format source files to match our standard format, which has |
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four-space tabs, and an indenting format specified by flags to the your |
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operating system's utility indent. |
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2) What books are good for developers? |
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I have two good books, An Introduction to Database Systems, by C.J. Date, |
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Addison, Wesley and A Guide to the SQL Standard, by C.J. Date, et. al, |
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Addison, Wesley. |
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3) Why do we use palloc() and pfree() to allocate memory? |
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palloc() and pfree() are used in place of malloc() and free() because we |
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automatically free all memory allocated when a transaction completes. This |
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makes it easier to make sure we free memory that gets allocated in one |
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place, but only freed much later. There are several contexts that memory can |
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be allocated in, and this controls when the allocated memory is |
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automatically freed by the backend. |
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4) Why do we use Node and List to make data structures? |
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We do this because this allows a consistent way to pass data inside the |
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backend in a flexible way. Every node has a NodeTag which specifies what |
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type of data is inside the Node. Lists are lists of Nodes. lfirst(), |
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lnext(), and foreach() are used to get, skip, and traverse through Lists. |
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5) How do I add a feature or fix a bug? |
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The source code is over 250,000 lines. Many problems/features are isolated |
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to one specific area of the code. Others require knowledge of much of the |
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source. If you are confused about where to start, ask the hackers list, and |
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they will be glad to assess the complexity and give pointers on where to |
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start. |
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Another thing to keep in mind is that many fixes and features can be added |
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with surprisingly little code. I often start by adding code, then looking at |
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other areas in the code where similar things are done, and by the time I am |
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finished, the patch is quite small and compact. |
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When adding code, keep in mind that it should use the existing facilities in |
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the source, for performance reasons and for simplicity. Often a review of |
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existing code doing similar things is helpful. |
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6) How do I download/update the current source tree? |
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There are several ways to obtain the source tree. Occasional developers can |
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just get the most recent source tree snapshot from ftp.postgresql.org. For |
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regular developers, you can get CVSup, which is available from |
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ftp.postgresql.org too. CVSup allows you to download the source tree, then |
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occasionally update your copy of the source tree with any new changes. Using |
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CVSup, you don't have to download the entire source each time, only the |
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changed files. CVSup does not allow developers to update the source tree. |
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To update the source tree, there are two ways. You can generate a patch |
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against your current source tree, perhaps using the make_diff tools |
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mentioned above, and send them to the patches list. They will be reviewed, |
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and applied in a timely manner. If the patch is major, and we are in beta |
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testing, the developers may wait for the final release before applying your |
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patches. |
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For hard-core developers, Marc(scrappy@postgresql.org) will give you a Unix |
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shell account on postgresql.org, and you can ftp your files into your |
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account, patch, and cvs install the changes directly into the source tree. |
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6) How do I test my changes? |
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First, use psql to make sure it is working as you expect. Then run |
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src/test/regress and get the output of src/test/regress/checkresults with |
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and without your changes, to see that your patch does not change the |
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regression test in unexpected ways. This practice has saved me many times. |
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The regression tests test the code in ways I would never do, and has caught |
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many bugs in my patches. By finding the problems now, you save yourself a |
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lot of debugging later when things are broken, and you can't figure out when |
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it happened. |
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