+++ /dev/null
-<!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>
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-<title>How PostgreSQL Processes a Query</title>
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-<body bgcolor="#FFFFFF" text="#000000" link="#FF0000"
-vlink="#A00000" alink="#0000FF">
-<h1>How PostgreSQL Processes a Query</h1>
-
-<h2>by Bruce Momjian</h2>
-
-<center>
-<h3><i>Click on an item</i> to see more detail or look at the full
-<a href="backend_dirs.html">index.</a></h3>
-
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-<area coords="45, 335, 175, 365" href="backend_dirs.html#rewrite" alt="rewrite" />
-<area coords="45, 400, 175, 430" href="backend_dirs.html#optimizer_path" alt="path" />
-<area coords="45, 460, 175, 490" href="backend_dirs.html#optimizer_plan" alt="plan" />
-<area coords="45, 525, 175, 555" href="backend_dirs.html#executor" alt="executor" />
-<area coords="0, 640, 130, 675" href="backend_dirs.html#utils" alt="utils" />
-<area coords="175, 640, 300, 675" href="backend_dirs.html#catalog" alt="catalog" />
-<area coords="330, 640, 475, 675" href="backend_dirs.html#storage" alt="storage" />
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-<area coords="255, 705, 380, 735" href="backend_dirs.html#nodes" alt="nodes" />
-</map>
-</center>
-
-<br />
-
-<p>A query comes to the backend via data packets arriving through
-TCP/IP or Unix Domain sockets. It is loaded into a string, and
-passed to the <a href="../../backend/parser">parser,</a> where the
-lexical scanner, <a href="../../backend/parser/scan.l">scan.l,</a>
-breaks the query up into tokens(words). The parser uses <a
-href="../../backend/parser/gram.y">gram.y</a> and the tokens to
-identify the query type, and load the proper query-specific
-structure, like <a
-href="../../include/nodes/parsenodes.h">CreateStmt</a> or <a
-href="../../include/nodes/parsenodes.h">SelectStmt.</a></p>
-
-<p>The statement is then identified as complex (<i>SELECT / INSERT /
-UPDATE / DELETE</i>) or a simple, e.g <i> CREATE USER, ANALYZE, </i>,
-etc. Simple utility commands are processed by statement-specific
-functions in <a href="../../backend/commands">backend/commands.</a>
-Complex statements require more handling.</p>
-
-<p>The parser takes a complex query, and creates a <a
-href="../../include/nodes/parsenodes.h">Query</a> structure that
-contains all the elements used by complex queries. Query.qual holds
-the <i>WHERE</i> clause qualification, which is filled in by <a
-href="../../backend/parser/parse_clause.c">transformWhereClause().</a>
-Each table referenced in the query is represented by a <a
-href="../../include/nodes/parsenodes.h">RangeTableEntry,</a> and
-they are linked together to form the <i>range table</i> of the
-query, which is generated by <a
-href="../../backend/parser/parse_clause.c">transformFromClause().</a>
-Query.rtable holds the query's range table.</p>
-
-<p>Certain queries, like <i>SELECT,</i> return columns of data.
-Other queries, like <i>INSERT</i> and <i>UPDATE,</i> specify the
-columns modified by the query. These column references are
-converted to <a
-href="../../include/nodes/primnodes.h">TargetEntry</a> entries,
-which are linked together to make up the <i>target list</i> of the
-query. The target list is stored in Query.targetList, which is
-generated by <a
-href="../../backend/parser/parse_target.c">transformTargetList().</a></p>
-
-<p>Other query elements, like aggregates(<i>SUM()</i>), <i>GROUP
-BY,</i> and <i>ORDER BY</i> are also stored in their own Query
-fields.</p>
-
-<p>The next step is for the Query to be modified by any
-<i>VIEWS</i> or <i>RULES</i> that may apply to the query. This is
-performed by the <a href="../../backend/rewrite">rewrite</a>
-system.</p>
-
-<p>The <a href="../../backend/optimizer">optimizer</a> takes the
-Query structure and generates an optimal <a
-href="../../include/nodes/plannodes.h">Plan,</a> which contains the
-operations to be performed to execute the query. The <a
-href="../../backend/optimizer/path">path</a> module determines the
-best table join order and join type of each table in the
-RangeTable, using Query.qual(<i>WHERE</i> clause) to consider
-optimal index usage.</p>
-
-<p>The Plan is then passed to the <a
-href="../../backend/executor">executor</a> for execution, and the
-result returned to the client. The Plan is actually as set of nodes,
-arranged in a tree structure with a top-level node, and various
-sub-nodes as children.</p>
-
-<p>There are many other modules that support this basic
-functionality. They can be accessed by clicking on the
-flowchart.</p>
-
-<hr />
-<p>Another area of interest is the shared memory area, which
-contains data accessible to all backends. It has recently used
-data/index blocks, locks, backend process information, and lookup
-tables for these structures:</p>
-
-<ul>
-<li>ShmemIndex - lookup shared memory addresses using structure
-names</li>
-
-<li><a href="../../include/storage/buf_internals.h">Buffer
-Descriptor</a> - control header for buffer cache block</li>
-
-<li><a href="../../include/storage/buf_internals.h">Buffer
-Block</a> - data/index buffer cache block</li>
-
-<li>Shared Buffer Lookup Table - lookup of buffer cache block
-addresses using table name and block number( <a
-href="../../include/storage/buf_internals.h">BufferTag</a>)</li>
-
-<li>Lock Manager Tables (lock hash) - the <a
-href="../../include/storage/lock.h">LOCK</a> structure, looked up
-using a <a href="../../include/storage/lock.h">LOCKTAG</a>.
-A LOCK structure exists for each lockable object that is currently
-locked by any backend. Also, there is a subsidiary <a
-href="../../include/storage/lock.h">PROCLOCK</a> structure for each
-backend currently interested in a given LOCK</li>
-
-<li><a href="../../include/storage/proc.h">PGPROC Structures</a> -
-information about each backend, including locks held/waiting</li>
-</ul>
-
-<p>Each data structure is created by calling <a
-href="../../backend/storage/ipc/shmem.c">ShmemInitStruct(),</a> and
-the lookups are created by <a
-href="../../backend/storage/ipc/shmem.c">ShmemInitHash().</a></p>
-
-<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>
projects / postgresql / commitdiff
