350 lines
13 KiB
HTML
350 lines
13 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
|
|
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|
<html xmlns="http://www.w3.org/1999/xhtml">
|
|
<head>
|
|
<meta name="generator"
|
|
content="HTML Tidy for BSD/OS (vers 1st July 2002), see www.w3.org" />
|
|
<title>PostgreSQL Backend Directories</title>
|
|
</head>
|
|
<body bgcolor="#FFFFFF" text="#000000" link="#FF0000"
|
|
vlink="#A00000" alink="#0000FF">
|
|
<h1>PostgreSQL Backend Directories</h1>
|
|
|
|
<h2>by Bruce Momjian</h2>
|
|
|
|
<hr />
|
|
<p><em>Click on any of the section headings to see the source code
|
|
for that section.</em></p>
|
|
|
|
<h2><a id="bootstrap" name="bootstrap"></a> <a
|
|
href="../../backend/bootstrap">bootstrap</a> - creates initial
|
|
template database via initdb</h2>
|
|
|
|
<p>Because PostgreSQL requires access to system tables for almost
|
|
every operation, getting those system tables in place is a problem.
|
|
You can't just create the tables and insert data into them in the
|
|
normal way, because table creation and insertion requires the
|
|
tables to already exist. This code <i>jams</i> the data directly
|
|
into tables using a special syntax used only by the bootstrap
|
|
procedure.</p>
|
|
|
|
<h2><a id="main" name="main"></a> <a
|
|
href="../../backend/main">main</a> - passes control to postmaster
|
|
or postgres</h2>
|
|
|
|
<p>This checks the process name(argv[0]) and various flags, and
|
|
passes control to the postmaster or postgres backend code.</p>
|
|
|
|
<h2><a id="postmaster" name="postmaster"></a> <a
|
|
href="../../backend/postmaster">postmaster</a> - controls postgres
|
|
server startup/termination</h2>
|
|
|
|
<p>This creates shared memory, and then goes into a loop waiting
|
|
for connection requests. When a connection request arrives, a
|
|
<i>postgres</i> backend is started, and the connection is passed to
|
|
it.</p>
|
|
|
|
<h2><a id="libpq" name="libpq"></a> <a
|
|
href="../../backend/libpq">libpq</a> - backend libpq library
|
|
routines</h2>
|
|
|
|
<p>This handles communication to the client processes.</p>
|
|
|
|
<h2><a id="tcop" name="tcop"></a> <a
|
|
href="../../backend/tcop">tcop</a> - traffic cop, dispatches
|
|
request to proper module</h2>
|
|
|
|
<p>This contains the <i>postgres</i> backend main handler, as well
|
|
as the code that makes calls to the parser, optimizer, executor,
|
|
and <i>/commands</i> functions.</p>
|
|
|
|
<h2><a id="parser" name="parser"></a> <a
|
|
href="../../backend/parser">parser</a> - converts SQL query to
|
|
query tree</h2>
|
|
|
|
<p>This converts SQL queries coming from <i>libpq</i> into
|
|
command-specific structures to be used the optimizer/executor,
|
|
or <i>/commands</i> routines. The SQL is lexically analyzed into
|
|
keywords, identifiers, and constants, and passed to the parser. The
|
|
parser creates command-specific structures to hold the elements of
|
|
the query. The command-specific structures are then broken apart,
|
|
checked, and passed to <i>/commands</i> processing routines, or
|
|
converted into <i>Lists</i> of <i>Nodes</i> to be handled by the
|
|
optimizer and executor.</p>
|
|
|
|
<h2><a id="rewrite" name="rewrite"></a> <a
|
|
href="../../backend/rewrite">rewrite</a> - rule and views
|
|
support</h2>
|
|
|
|
<h2><a id="optimizer" name="optimizer"></a> <a
|
|
href="../../backend/optimizer">optimizer</a> - creates path and
|
|
plan</h2>
|
|
|
|
<p>This uses the parser output to generate an optimal plan for the
|
|
executor.</p>
|
|
|
|
<h3><a id="optimizer_path" name="optimizer_path"></a> <a
|
|
href="../../backend/optimizer/path">optimizer/path</a> - creates
|
|
path from parser output</h3>
|
|
|
|
<p>This takes the parser query output, and generates all possible
|
|
methods of executing the request. It examines table join order,
|
|
<i>where</i> clause restrictions, and optimizer table statistics to
|
|
evaluate each possible execution method, and assigns a cost to
|
|
each.</p>
|
|
|
|
<h3><a id="optimizer_geqo" name="optimizer_geqo"></a> <a
|
|
href="../../backend/optimizer/geqo">optimizer/geqo</a> - genetic
|
|
query optimizer</h3>
|
|
|
|
<p><i>optimizer/path</i> evaluates all possible ways to join the
|
|
requested tables. When the number of tables becomes great, the
|
|
number of tests made becomes great too. The Genetic Query Optimizer
|
|
considers each table separately, then figures the most optimal
|
|
order to perform the join. For a few tables, this method takes
|
|
longer, but for a large number of tables, it is faster. There is an
|
|
option to control when this feature is used.</p>
|
|
|
|
<h3><a id="optimizer_plan" name="optimizer_plan"></a> <a
|
|
href="../../backend/optimizer/plan">optimizer/plan</a> - optimizes
|
|
path output</h3>
|
|
|
|
<p>This takes the <i>optimizer/path</i> output, chooses the path
|
|
with the least cost, and creates a plan for the executor.</p>
|
|
|
|
<h3><a id="optimizer_prep" name="optimizer_prep"></a> <a
|
|
href="../../backend/optimizer/prep">optimizer/prep</a> - handle
|
|
special plan cases</h3>
|
|
|
|
<p>This does special plan processing.</p>
|
|
|
|
<h3><a id="optimizer_util" name="optimizer_util"></a> <a
|
|
href="../../backend/optimizer/util">optimizer/util</a> - optimizer
|
|
support routines</h3>
|
|
|
|
<p>This contains support routines used by other parts of the
|
|
optimizer.</p>
|
|
|
|
<h2><a id="executor" name="executor"></a> <a
|
|
href="../../backend/executor">executor</a> - executes complex node
|
|
plans from optimizer</h2>
|
|
|
|
<p>This handles <i>select, insert, update,</i> and <i>delete</i>
|
|
statements. The operations required to handle these statement types
|
|
include heap scans, index scans, sorting, joining tables, grouping,
|
|
aggregates, and uniqueness.</p>
|
|
|
|
<h2><a id="commands" name="commands"></a> <a
|
|
href="../../backend/commands">commands</a> - commands that do not
|
|
require the executor</h2>
|
|
|
|
<p>These process SQL commands that do not require complex handling.
|
|
It includes <i>vacuum, copy, alter, create table, create type,</i>
|
|
and many others. The code is called with the structures generated
|
|
by the parser. Most of the routines do some processing, then call
|
|
lower-level functions in the catalog directory to do the actual
|
|
work.</p>
|
|
|
|
<h2><a id="catalog" name="catalog"></a> <a
|
|
href="../../backend/catalog">catalog</a> - system catalog
|
|
manipulation</h2>
|
|
|
|
<p>This contains functions that manipulate the system tables or
|
|
catalogs. Table, index, procedure, operator, type, and aggregate
|
|
creation and manipulation routines are here. These are low-level
|
|
routines, and are usually called by upper routines that pre-format
|
|
user requests into a predefined format.</p>
|
|
|
|
<h2><a id="storage" name="storage"></a> <a
|
|
href="../../backend/storage">storage</a> - manages various storage
|
|
systems</h2>
|
|
|
|
<p>These allow uniform resource access by the backend.<br />
|
|
<br />
|
|
<a id="storage_buffer" name="storage_buffer"></a> <a
|
|
href="../../backend/storage/buffer">storage/buffer</a> - shared
|
|
buffer pool manager<br />
|
|
<a id="storage_file" name="storage_file"></a> <a
|
|
href="../../backend/storage/file">storage/file</a> - file
|
|
manager<br />
|
|
<a id="storage_freespace" name="storage_freespace"></a> <a
|
|
href="../../backend/storage/freespace">storage/freespace</a> - free
|
|
space map<br />
|
|
<a id="storage_ipc" name="storage_ipc"></a> <a
|
|
href="../../backend/storage/ipc">storage/ipc</a> - semaphores and
|
|
shared memory<br />
|
|
<a id="storage_large_object" name="storage_large_object"></a> <a
|
|
href="../../backend/storage/large_object">storage/large_object</a>
|
|
- large objects<br />
|
|
<a id="storage_lmgr" name="storage_lmgr"></a> <a
|
|
href="../../backend/storage/lmgr">storage/lmgr</a> - lock
|
|
manager<br />
|
|
<a id="storage_page" name="storage_page"></a> <a
|
|
href="../../backend/storage/page">storage/page</a> - page
|
|
manager<br />
|
|
<a id="storage_smgr" name="storage_smgr"></a> <a
|
|
href="../../backend/storage/smgr">storage/smgr</a> - storage/disk
|
|
manager<br />
|
|
<br />
|
|
</p>
|
|
|
|
<h2><a id="access" name="access"></a> <a
|
|
href="../../backend/access">access</a> - various data access
|
|
methods</h2>
|
|
|
|
<p>These control the way data is accessed in heap, indexes, and
|
|
transactions.<br />
|
|
<br />
|
|
<a id="access_common" name="access_common"></a> <a
|
|
href="../../backend/access/common">access/common</a> - common
|
|
access routines<br />
|
|
<a id="access_gist" name="access_gist"></a> <a
|
|
href="../../backend/access/gist">access/gist</a> - easy-to-define
|
|
access method system<br />
|
|
<a id="access_hash" name="access_hash"></a> <a
|
|
href="../../backend/access/hash">access/hash</a> - hash<br />
|
|
<a id="access_heap" name="access_heap"></a> <a
|
|
href="../../backend/access/heap">access/heap</a> - heap is use to
|
|
store data rows<br />
|
|
<a id="access_index" name="access_index"></a> <a
|
|
href="../../backend/access/index">access/index</a> - used by all
|
|
index types<br />
|
|
<a id="access_nbtree" name="access_nbtree"></a> <a
|
|
href="../../backend/access/nbtree">access/nbtree</a> - Lehman and
|
|
Yao's btree management algorithm<br />
|
|
<a id="access_transam" name="access_transam"></a> <a
|
|
href="../../backend/access/transam">access/transam</a> -
|
|
transaction manager (BEGIN/ABORT/COMMIT)<br />
|
|
<br />
|
|
</p>
|
|
|
|
<h2><a id="nodes" name="nodes"></a> <a
|
|
href="../../backend/nodes">nodes</a> - creation/manipulation of
|
|
nodes and lists</h2>
|
|
|
|
<p>PostgreSQL stores information about SQL queries in structures
|
|
called nodes. <i>Nodes</i> are generic containers that have a
|
|
<i>type</i> field and then a type-specific data section. Nodes are
|
|
usually placed in <i>Lists.</i> A <i>List</i> is container with an
|
|
<i>elem</i> element, and a <i>next</i> field that points to the
|
|
next <i>List.</i> These <i>List</i> structures are chained together
|
|
in a forward linked list. In this way, a chain of <i>List</i> s can
|
|
contain an unlimited number of <i>Node</i> elements, and each
|
|
<i>Node</i> can contain any data type. These are used extensively
|
|
in the parser, optimizer, and executor to store requests and
|
|
data.</p>
|
|
|
|
<h2><a id="utils" name="utils"></a> <a
|
|
href="../../backend/utils">utils</a> - support routines</h2>
|
|
|
|
<h3><a id="utils_adt" name="utils_adt"></a> <a
|
|
href="../../backend/utils/adt">utils/adt</a> - built-in data type
|
|
routines</h3>
|
|
|
|
<p>This contains all the PostgreSQL builtin data types.</p>
|
|
|
|
<h3><a id="utils_cache" name="utils_cache"></a> <a
|
|
href="../../backend/utils/cache">utils/cache</a> -
|
|
system/relation/function cache routines</h3>
|
|
|
|
<p>PostgreSQL supports arbitrary data types, so no data types are
|
|
hard-coded into the core backend routines. When the backend needs
|
|
to find out about a type, is does a lookup of a system table.
|
|
Because these system tables are referred to often, a cache is
|
|
maintained that speeds lookups. There is a system relation cache, a
|
|
function/operator cache, and a relation information cache. This
|
|
last cache maintains information about all recently-accessed
|
|
tables, not just system ones.</p>
|
|
|
|
<h3><a id="utils_error" name="utils_error"></a> <a
|
|
href="../../backend/utils/error">utils/error</a> - error reporting
|
|
routines</h3>
|
|
|
|
<p>Reports backend errors to the front end.</p>
|
|
|
|
<h3><a id="utils_fmgr" name="utils_fmgr"></a> <a
|
|
href="../../backend/utils/fmgr">utils/fmgr</a> - function
|
|
manager</h3>
|
|
|
|
<p>This handles the calling of dynamically-loaded functions, and
|
|
the calling of functions defined in the system tables.</p>
|
|
|
|
<h3><a id="utils_hash" name="utils_hash"></a> <a
|
|
href="../../backend/utils/hash">utils/hash</a> - hash routines for
|
|
internal algorithms</h3>
|
|
|
|
<p>These hash routines are used by the cache and memory-manager
|
|
routines to do quick lookups of dynamic data storage structures
|
|
maintained by the backend.</p>
|
|
|
|
<h3><a id="utils_init" name="utils_init"></a> <a
|
|
href="../../backend/utils/init">utils/init</a> - various
|
|
initialization stuff</h3>
|
|
|
|
<h3><a id="utils_mb" name="utils_mb"></a> <a
|
|
href="../../backend/utils/mb">utils/mb</a> - single and multibyte
|
|
encoding</h3>
|
|
|
|
<h3><a id="utils_misc" name="utils_misc"></a> <a
|
|
href="../../backend/utils/misc">utils/misc</a> - miscellaneous
|
|
stuff</h3>
|
|
|
|
<h3><a id="utils_mmgr" name="utils_mmgr"></a> <a
|
|
href="../../backend/utils/mmgr">utils/mmgr</a> - memory
|
|
manager(process-local memory)</h3>
|
|
|
|
<p>When PostgreSQL allocates memory, it does so in an explicit
|
|
context. Contexts can be statement-specific, transaction-specific,
|
|
or persistent/global. By doing this, the backend can easily free
|
|
memory once a statement or transaction completes.</p>
|
|
|
|
<h3><a id="utils_resowner" name="utils_resowner"></a> <a
|
|
href="../../backend/utils/resowner">utils/resowner</a> - resource
|
|
owner tracking</h3>
|
|
|
|
<h3><a id="utils_sort" name="utils_sort"></a> <a
|
|
href="../../backend/utils/sort">utils/sort</a> - sort routines for
|
|
internal algorithms</h3>
|
|
|
|
<p>When statement output must be sorted as part of a backend
|
|
operation, this code sorts the tuples, either in memory or using
|
|
disk files.</p>
|
|
|
|
<h3><a id="utils_time" name="utils_time"></a> <a
|
|
href="../../backend/utils/time">utils/time</a> - transaction time
|
|
qualification routines</h3>
|
|
|
|
<p>These routines do checking of tuple internal columns to
|
|
determine if the current row is still valid, or is part of a
|
|
non-committed transaction or superseded by a new row.</p>
|
|
|
|
<h2><a id="include" name="include"></a> <a
|
|
href="../../backend/include">include</a> - include files</h2>
|
|
|
|
<p>There are include directories for each subsystem.</p>
|
|
|
|
<h2><a id="lib" name="lib"></a> <a href="../../backend/lib">lib</a>
|
|
- support library</h2>
|
|
|
|
<p>This houses several generic routines.</p>
|
|
|
|
<h2><a id="regex" name="regex"></a> <a
|
|
href="../../backend/regex">regex</a> - regular expression
|
|
library</h2>
|
|
|
|
<p>This is used for regular expression handling in the backend,
|
|
i.e. '~'.</p>
|
|
|
|
<h2><a id="port" name="port"></a> <a
|
|
href="../../backend/port">port</a> - compatibility routines</h2>
|
|
|
|
<br />
|
|
|
|
<hr />
|
|
<small>Maintainer: Bruce Momjian ( <a
|
|
href="mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</a>
|
|
)<br />
|
|
Last updated: Fri May 6 14:22:27 EDT 2005</small>
|
|
</body>
|
|
</html>
|