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| author | Bruce Momjian <bruce@momjian.us> | 1998-06-30 04:35:34 +0000 |
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 1998-06-30 04:35:34 +0000 |
| commit | 34d595729a73ff83794203a8b12259ae22772674 (patch) | |
| tree | e0bd7c6efa466e648d3592987e09278199b7cce6 | |
| parent | 2584029e31dc4abda9ae676abc6e2a9c7d1e9553 (diff) | |
| download | postgresql-34d595729a73ff83794203a8b12259ae22772674.tar.gz postgresql-34d595729a73ff83794203a8b12259ae22772674.zip | |
update
| -rw-r--r-- | src/tools/backend/index.html | 47 |
1 files changed, 25 insertions, 22 deletions
diff --git a/src/tools/backend/index.html b/src/tools/backend/index.html index 3f032e081c3..b94f39be662 100644 --- a/src/tools/backend/index.html +++ b/src/tools/backend/index.html @@ -1,31 +1,31 @@ <HTML> <HEAD> -<TITLE>PostgreSQL Backend Flowchart</TITLE> +<TITLE>How PostgreSQL Processes a Query</TITLE> </HEAD> <BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#FF0000" VLINK="#A00000" ALINK="#0000FF"> <H1 ALIGN=CENTER> -PostgreSQL Backend Flowchart +How PostgreSQL Processes a Query </H1> <H2 ALIGN=CENTER> by Bruce Momjian </H2> <P> -A query come into the backend via data packets coming in through TCP/IP -and Unix Domain sockets. It is loaded into a string, and passed to +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 or SelectStmt.</A> +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> -The query is then identified as a <I>Utility</I> function or a more -complex query. A <I>Utility</I> query is processed by a -query-specific function in <A HREF="../../backend/commands"> -commands.</A> A complex query, like <CODE>SELECT, UPDATE,</CODE> and +The query is then identified as a <I>Utility</I> query or a more complex +query. A <I>Utility</I> query is processed by a query-specific function +in <A HREF="../../backend/commands"> commands.</A> A complex query, like +<CODE>SELECT, UPDATE,</CODE> and <CODE>DELETE</CODE> requires much more handling. <P> The parser takes a complex query, and creates a @@ -37,7 +37,7 @@ 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"> -makeRangeTable().</A> Query.rtable holds the queries range table. +makeRangeTable().</A> Query.rtable holds the query's range table. <P> Certain queries, like <CODE>SELECT,</CODE> return columns of data. Other queries, like <CODE>INSERT</CODE> and <CODE>UPDATE,</CODE> specify the columns @@ -48,7 +48,7 @@ target list is stored in Query.targetList, which is generated by <A HREF="../../backend/parser/parse_target.c">transformTargetList().</A> <P> Other query elements, like aggregates(<CODE>SUM()</CODE>), <CODE>GROUP BY,</CODE> -<CODE>ORDER BY</CODE> are also stored in their own Query fields. +and <CODE>ORDER BY</CODE> are also stored in their own Query fields. <P> The next step is for the Query to be modified by any <CODE>VIEWS</CODE> or <CODE>RULES</CODE> that may apply to the query. This is performed by the <A @@ -69,21 +69,22 @@ returned to the client. There are many other modules that support this basic functionality. They can be accessed by clicking on the flowchart. <P> -Another area of interest is the shared memory area, containing table -data/index blocks, locks, backend information, and lookup tables for -these structures: +Another area of interest is the shared memory area, which contains data +accessable to all backends. It has table recently used data/index +blocks, locks, backend information, and lookup tables for these +structures: <UL> <LI>ShmemIndex - lookup shared memory addresses using structure names <LI><A HREF="../../include/storage/buf_internals.h">Buffer -Descriptors</A> - control header for buffer cache block -<LI><A HREF="../../include/storage/buf_internals.h">Buffer Blocks</A> - +Descriptor</A> - control header for buffer cache block +<LI><A HREF="../../include/storage/buf_internals.h">Buffer Block</A> - data/index buffer cache block -<LI>Shared Buf Lookup Table - lookup of buffer cache block address using +<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>MultiLevelLockTable (ctl) - <A -HREF="../../include/storage/lock.h">LOCKCTL</A> control structure for -each locking method. Currently, only multi-level locking is used. +<LI>MultiLevelLockTable (ctl) - control structure for +each locking method. Currently, only multi-level locking is used(<A +HREF="../../include/storage/lock.h">LOCKMETHODCTL</A>). <LI>MultiLevelLockTable (lock hash) - the <A HREF="../../include/storage/lock.h">LOCK</A> structure, looked up using relation, database object ids(<A @@ -105,7 +106,9 @@ 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> +<P> <CENTER> <EM><BIG> Click on an item to see more detail or |