diff --git a/src/tools/backend/README b/src/tools/backend/README deleted file mode 100644 index 2b8692d39395b077f5c58c126c522307bfc558b7..0000000000000000000000000000000000000000 --- a/src/tools/backend/README +++ /dev/null @@ -1,4 +0,0 @@ -src/tools/backend/README - -Just point your browser at the index.html file, and click on the -flowchart to see the description and source code. diff --git a/src/tools/backend/backend_dirs.html b/src/tools/backend/backend_dirs.html deleted file mode 100644 index 16bd894582e9ea44b74814ebfb39919a3230fe40..0000000000000000000000000000000000000000 --- a/src/tools/backend/backend_dirs.html +++ /dev/null @@ -1,349 +0,0 @@ -<!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> diff --git a/src/tools/backend/flow.fig b/src/tools/backend/flow.fig deleted file mode 100644 index b10aa2cfc48e58c2c9a95392343528c28736150e..0000000000000000000000000000000000000000 --- a/src/tools/backend/flow.fig +++ /dev/null @@ -1,143 +0,0 @@ -#FIG 3.2 Produced by xfig version 3.2.5 -Portrait -Center -Inches -Letter -88.00 -Single --2 -1200 2 -0 32 #919191 -0 33 #c5ddc1 -2 4 0 1 -1 26 1 0 20 0.000 0 0 7 0 0 5 - 3600 900 1200 900 1200 300 3600 300 3600 900 -2 4 0 1 -1 4 1 0 20 0.000 0 0 7 0 0 5 - 3600 2100 1200 2100 1200 1500 3600 1500 3600 2100 -2 4 0 1 -1 0 1 0 20 0.000 0 0 7 0 0 5 - 7500 1500 5100 1500 5100 900 7500 900 7500 1500 -2 4 0 1 -1 31 1 0 20 0.000 0 0 7 0 0 5 - 3600 3300 1200 3300 1200 2700 3600 2700 3600 3300 -2 4 0 1 -1 8 1 0 20 0.000 0 0 7 0 0 5 - 3600 6000 1200 6000 1200 5400 3600 5400 3600 6000 -2 4 0 1 -1 31 1 0 20 0.000 0 0 7 0 0 5 - 7500 3300 5100 3300 5100 2700 7500 2700 7500 3300 -2 4 0 1 -1 8 1 0 20 0.000 0 0 7 0 0 5 - 3600 8400 1200 8400 1200 7800 3600 7800 3600 8400 -2 4 0 1 -1 8 1 0 20 0.000 0 0 7 0 0 5 - 3600 9600 1200 9600 1200 9000 3600 9000 3600 9600 -2 1 2 2 -1 7 0 0 -1 3.000 0 1 -1 1 1 2 - 0 0 2.00 80.00 150.00 - 0 0 2.00 80.00 150.00 - 4500 1425 5135 1194 -2 1 2 2 -1 7 0 0 -1 4.000 0 1 -1 1 1 2 - 0 0 2.00 80.00 150.00 - 0 0 2.00 80.00 150.00 - 4725 2025 5160 1467 -2 1 0 2 20 7 1 0 -1 0.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 2400 2100 2400 2700 -2 1 0 2 31 7 1 0 -1 0.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 2400 3300 2400 4275 -2 4 0 1 -1 8 1 0 20 0.000 0 0 7 0 0 5 - 3600 7200 1200 7200 1200 6600 3600 6600 3600 7200 -2 4 0 1 -1 8 1 0 20 0.000 0 0 7 0 0 5 - 3600 10800 1200 10800 1200 10200 3600 10200 3600 10800 -2 4 0 1 -1 8 1 0 20 0.000 0 0 7 0 0 5 - 3600 4800 1200 4800 1200 4200 3600 4200 3600 4800 -2 1 1 2 32 7 1 0 -1 4.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 2400 8400 2400 9000 -2 1 1 2 32 7 1 0 -1 4.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 2400 7200 2400 7800 -2 1 1 2 32 7 1 0 -1 4.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 2400 6000 2400 6600 -2 1 1 2 32 7 1 0 -1 4.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 2400 4800 2400 5400 -2 1 1 2 32 7 1 0 -1 4.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 3600 5700 5100 5700 -2 1 0 2 25 7 0 0 -1 0.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.50 - 2400 900 2400 1500 -2 4 0 1 -1 8 1 0 20 0.000 0 0 7 0 0 5 - 7500 6000 5100 6000 5100 5400 7500 5400 7500 6000 -2 4 0 1 33 33 3 0 20 0.000 0 0 40 0 0 5 - 8700 11100 300 11100 300 3600 8700 3600 8700 11100 -2 1 0 2 29 7 0 0 -1 0.000 0 0 -1 1 1 2 - 0 0 2.00 150.00 180.00 - 0 0 2.00 150.00 180.00 - 3150 13050 3150 13650 -2 1 0 2 29 7 0 0 -1 0.000 0 0 -1 1 1 2 - 0 0 2.00 150.00 180.00 - 0 0 2.00 150.00 180.00 - 1500 12450 1500 11850 -2 4 0 1 -1 29 1 0 20 0.000 0 0 7 0 0 5 - 2700 13050 300 13050 300 12450 2700 12450 2700 13050 -2 4 0 1 -1 29 1 0 20 0.000 0 0 7 0 0 5 - 6000 13050 3600 13050 3600 12450 6000 12450 6000 13050 -2 4 0 1 -1 29 1 0 20 0.000 0 0 7 0 0 5 - 7500 14250 5100 14250 5100 13650 7500 13650 7500 14250 -2 4 0 1 -1 29 1 0 20 0.000 0 0 7 0 0 5 - 4200 14250 1800 14250 1800 13650 4200 13650 4200 14250 -2 1 0 2 29 7 0 0 -1 0.000 0 0 -1 1 1 2 - 0 0 2.00 150.00 180.00 - 0 0 2.00 150.00 180.00 - 4800 12450 4800 11850 -2 1 0 2 29 7 0 0 -1 0.000 0 0 -1 1 1 2 - 0 0 2.00 150.00 180.00 - 0 0 2.00 150.00 180.00 - 6300 13050 6300 13650 -2 4 0 1 -1 29 1 0 20 0.000 0 0 7 0 0 5 - 9300 13050 6600 13050 6600 12450 9300 12450 9300 13050 -2 1 0 2 29 7 0 0 -1 0.000 0 0 -1 1 1 2 - 0 0 2.00 150.00 180.00 - 0 0 2.00 150.00 180.00 - 7950 11850 7950 12450 -2 1 1 2 5 7 1 0 -1 4.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 2400 6000 2400 6600 -2 1 1 2 32 7 1 0 -1 4.000 0 0 -1 1 0 2 - 0 0 2.00 150.00 180.00 - 2400 9600 2400 10200 -3 2 2 2 20 7 0 0 -1 6.000 1 1 0 5 - 0 0 2.00 150.00 180.00 - 2415 2140 3090 2440 5265 2515 6090 2590 6315 2740 - 0.000 -1.000 -1.000 -1.000 0.000 -3 0 1 2 32 7 1 0 -1 4.500 0 1 0 7 - 0 0 2.00 150.00 150.00 - 7500 5700 8400 5400 8400 4500 7800 3900 3600 3900 3000 3900 - 2700 4200 - 0.000 1.000 1.000 1.000 1.000 1.000 0.000 -3 0 1 2 32 7 0 0 -1 4.000 0 1 0 8 - 0 0 2.00 150.00 150.00 - 1125 10500 900 10350 675 9975 675 4350 900 3975 1350 3900 - 1800 3900 2100 4200 - 0.000 1.000 1.000 1.000 1.000 1.000 1.000 0.000 -4 1 5 2 0 28 18 0.0000 4 285 870 4350 5625 utility\001 -4 1 -1 0 0 16 18 0.0000 4 210 1455 2400 1950 Postmaster\001 -4 1 -1 0 0 16 18 0.0000 4 270 1125 2400 3150 Postgres\001 -4 1 -1 0 0 16 18 0.0000 4 270 1125 6300 3150 Postgres\001 -4 1 7 0 0 16 18 0.0000 4 270 720 6300 1350 Libpq\001 -4 1 -1 0 0 16 18 0.0000 4 210 615 2400 750 Main\001 -4 1 7 0 0 16 18 0.0000 4 210 1815 2400 9450 Generate Plan\001 -4 1 7 0 0 16 18 0.0000 4 270 1440 2400 5850 Traffic Cop\001 -4 1 7 0 0 16 18 0.0000 4 210 1980 2400 8250 Generate Paths\001 -4 1 5 2 0 28 18 0.0000 4 225 615 2400 9900 Plan\001 -4 1 5 2 0 28 18 0.0000 4 285 1920 2400 8700 Optimal Path\001 -4 1 5 2 0 28 18 0.0000 4 285 900 2400 6300 Query\001 -4 1 7 0 0 16 18 0.0000 4 210 1680 2400 10650 Execute Plan\001 -4 0 5 0 0 16 12 0.0000 4 210 2640 5250 6300 e.g. CREATE TABLE, COPY\001 -4 1 5 0 0 16 12 0.0000 4 195 3540 2400 6525 SELECT, INSERT, UPDATE, DELETE\001 -4 1 7 0 0 16 18 0.0000 4 270 1800 2400 7050 Rewrite Query\001 -4 1 7 0 0 16 18 0.0000 4 210 2130 2400 4650 Parse Statement\001 -4 1 7 0 0 16 18 0.0000 4 270 720 6300 5700 Utility\001 -4 1 7 0 0 16 18 0.0000 4 210 1335 6300 6000 Command\001 -4 1 -1 0 0 16 18 0.0000 4 270 2355 7950 12900 Storage Managers\001 -4 1 -1 0 0 16 18 0.0000 4 270 1020 4800 12900 Catalog\001 -4 1 -1 0 0 16 18 0.0000 4 210 915 1500 12900 Utilities\001 -4 1 -1 0 0 16 18 0.0000 4 210 2085 3000 14100 Access Methods\001 -4 1 -1 0 0 16 18 0.0000 4 210 1635 6300 14100 Nodes / Lists\001 diff --git a/src/tools/backend/flow.gif b/src/tools/backend/flow.gif deleted file mode 100644 index e0cd8db9b193c7667e00131fa3f3847af97daa14..0000000000000000000000000000000000000000 Binary files a/src/tools/backend/flow.gif and /dev/null differ diff --git a/src/tools/backend/index.html b/src/tools/backend/index.html deleted file mode 100644 index eb4978bfe04761cf2396c32bf7eb7bbb056b3314..0000000000000000000000000000000000000000 --- a/src/tools/backend/index.html +++ /dev/null @@ -1,155 +0,0 @@ -<!-- src/tools/backend/index.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>How PostgreSQL Processes a Query</title> -</head> -<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> - -<p><img src="flow.gif" usemap="#flowmap" alt="flowchart" /> - -<map name="flowmap" id="flowmap"> -<area coords="45, 0, 175, 30" href="backend_dirs.html#main" alt="main" /> -<area coords="255, 35, 380, 65" href="backend_dirs.html#libpq" alt="libpq" /> -<area coords="45, 65, 175, 95" href="backend_dirs.html#postmaster" alt="postmaster" /> -<area coords="45, 130, 175, 160" href="backend_dirs.html#tcop" alt="tcop" /> -<area coords="250, 130, 380, 160" href="backend_dirs.html#tcop" alt="tcop" /> -<area coords="45, 205, 175, 240" href="backend_dirs.html#parser" alt="parser" /> -<area coords="45, 270, 175, 300" href="backend_dirs.html#tcop" alt="tcop" /> -<area coords="255, 270, 380, 300" href="backend_dirs.html#commands" alt="commands" /> -<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" /> -<area coords="75, 700, 210, 735" href="backend_dirs.html#access" alt="access" /> -<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>