new DEV FAQ

Developers Frequently Asked Questions (FAQ) for PostgreSQL

Last updated: Thu Jan 22 15:04:10 EST 1998

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

The most recent version of this document can be viewed at the postgreSQL Web
site, http://postgreSQL.org.

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Questions answered:

1) General questions

1) What tools are available for developers?
2) What books are good for developers?
3) Why do we use palloc() and pfree() to allocate memory?
4) Why do we use Node() and List() to make data structures?
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1) What tools are available for developers?

Aside from the User documentation mentioned in the regular FAQ, there are
several development tools available. First, all the files in the /tools
directory are designed for developers.

        RELEASE_CHANGES         changes we have to make for each release
        SQL_keywords            standard SQL'92 keywords
        backend                 web flowchart of the backend directories
        ccsym                   find standard defines made by your compiler
        entab                   converts tabs to spaces, used by pgindent
        find_static             finds functions that could be made static
        find_typedef            get a list of typedefs in the source code
        make_ctags              make vi 'tags' file in each directory
        make_diff               make *.orig and diffs of source
        make_etags              make emacs 'etags' files
        make_keywords.README    make comparison of our keywords and SQL'92
        make_mkid               make mkid ID files
        mkldexport              create AIX exports file
        pgindent                indents C source files

Let me note some of these. If you point your browser at the tools/backend
directory, you will see all the backend components in a flow chart. You can
click on any one 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 Backend Flowchart.

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 mkid from ftp.postgresql.org. By running
tools/make_mkid, an archive of source symbols can be created that can be
rapidly queried like grep or edited.

make_diff has tools to create patch diff files that can be applied to the
distribution.

pgindent will format source files to match our standard format, which has
four-space tabs, and an indenting format specified by flags to the your
operating system's utility indent.

2) What books are good for developers?

I have two good books, An Introduction to Database Systems, by C.J. Date,
Addison, Wesley and A Guide to the SQL Standard, by C.J. Date, et. al,
Addison, Wesley.

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

palloc() and pfree() are used in place of malloc() and free() because we
automatically free all memory allocated when a transaction completes. This
makes it easier to make sure we free memory that gets allocated in one
place, but only freed much later. There are several contexts that memory can
be allocated in, and this controls when the allocated memory is
automatically freed by the backend.

4) 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 lists of Nodes. lfirst(),
lnext(), and foreach() are used to get, skip, and traverse throught Lists.

--
Bruce Momjian
maillist@candle.pha.pa.us