backend update.

diff --git a/src/tools/backend/index.html b/src/tools/backend/index.html
index dbf78042a4653886038e8cb85004fc92c5aa6135..7fe6440431990139f1e3566676ee3ee7febba90f 100644 (file)
--- a/src/tools/backend/index.html
+++ b/src/tools/backend/index.html
@@ -8,30 +8,30 @@ PostgreSQL Backend Flowchart
 
 
 by Bruce Momjian
- ALIGN=CENTER>
+
 
-Queries come into the backend via data packets coming in through TCP/IP
-and Unix Domain sockets.   They are loaded into a string, and passed to
+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
 the
 parser, where the lexical scanner,
 scan.l,
 breaks the query up into tokens(words).  The parser
 uses
 gram.y and the tokens to
-identify the query type, and load the proper query-type-specific
+identify the query type, and load the proper query-specific
 structure, like
 CreateStmt or SelectStmt.
 
 The query is then identified as a Utility function or a more
-complex query.  Utility queries are processed by a
-query-type-specific function in 
-commands. Complex queries, like SELECT, UPDATE,> and
-<I>DELETE require much more handling.  
+complex query.  A Utility query is processed by a
+query-specific function in 
+commands. A complex query, like SELECT, UPDATE,> and
+<B>DELETE requires much more handling.
 
-The parser takes the complex queries, and creates a
+The parser takes a complex query, and creates a
 Query structure that
 contains all the elements used by complex queries.  Query.qual holds the
-WHERE clause qualification, which is filled in by
+WHERE clause qualification, which is filled in by
 transformWhereClause().
 Each table referenced in the query is represented by a 
 HREF="../../include/nodes/parsenodes.h"> RangeTableEntry, and they
@@ -39,73 +39,70 @@ are linked together to form the range table of the query, which is
 generated by 
 makeRangeTable().  Query.rtable holds the queries range table.
 
-Certain queries, like SELECT, return columns of data.  Other queries,
-like INSERT and UPDATE, specify the columns modified by the query. 
-These column references are converted to 
-HREF="../../include/nodes/primnodes.h"> Resdom entries, which are
+Certain queries, like SELECT, return columns of data.  Other
+queries, like INSERT and UPDATE, specify the columns
+modified by the query.  These column references are converted to 
+HREF="../../include/nodes/primnodes.h">Resdom entries, which are
 linked together to make up the target list of the query. The
 target list is stored in Query.targetList, which is generated by
 transformTargetList().
 
-Other query elements, like aggregates(SUM()), GROUP BY, ORDER BY are
-also stored in their own Query fields.
+Other query elements, like aggregates(SUM()), GROUP BY,
+ORDER BY are also stored in their own Query fields.
 
-The next step is for the Query to be modified by any VIEWS or RULES that
-may apply to the query.  This is performed by the 
+The next step is for the Query to be modified by any VIEWS or
+RULES that may apply to the query.  This is performed by the 
 HREF="../../backend/rewrite">rewrite system.
 
 The optimizer takes the Query
-structure, and generates an optimal
-Plan containing the
-primitive operations to be performed by the executor to execute the
-query.  The path module
-determines the best table join order and join type of each table in the
-RangeTable, using Query.qual(WHERE clause) to consider optimal index
-usage.
+structure and generates an optimal 
+HREF="../..//include/nodes/plannodes.h">Plan, which contains the
+operations to be performed to execute the query.  The 
+HREF="../../backend/optimizer/path">path module determines the best
+table join order and join type of each table in the RangeTable, using
+Query.qual(WHERE clause) to consider optimal index usage.
 
 The Plan is then passed to the 
 HREF="../../backend/executor">executor for execution, and the result
-is returned to the client.
+returned to the client.
 
-There are many other modules that support this basic functionality. 
+There are many other modules that support this basic functionality.
 They can be accessed by clicking on the flowchart.
 
 Another area of interest is the shared memory area, containing
 table data/index blocks, locks, and backend information:
  
-ShmemIndex - contains an index of all other shared memory
-structures, allowing quick lookup of other structure locations in shared
-memory
+ShmemIndex - lookup of shared memory addresses using structure names
 Buffer
-Descriptors - control header for shared memory buffer block
-
-Buffer Blocks
-- block of table/index data shared by all backends
-Shared Buf Lookup Table - lookup to see if a requested buffer
-is already in the shared memory area
-LockTable
-- lock table structure, specifiying table, lock types, and
-backends holding or waiting on lock
-LockTable (lock hash) - lookup of LockTable structures using
-table name
+Descriptors - control header for buffer cache block
+Buffer Blocks -
+data/index buffer cache block
+Shared Buf Lookup Table - lookup of buffer cache block address using
+table name and block number(
+BufferTag)
+LockTable (ctl) - lock table
+structure, specifiying table, lock types, and backends holding or
+waiting on lock
+LockTable (lock hash) - lookup of LockTable structures using relation
+and database object ids
 LockTable (xid hash) - lookup of LockTable structures using
 transaction id
 Proc Header - information
 about each backend, including locks held/waiting,  indexed by process id
 
 Each data structure is created by calling 
-HREF="../../backend/storage/ipc/shmem.c"> ShmemInitStruct(), and
-the lookup hashes are created by
+HREF="../../backend/storage/ipc/shmem.c">ShmemInitStruct(), and
+the lookups are created by
 ShmemInitHash().
 
 
 
-Click on an item to see more detail or click
-here> to see the full index.
-EM>>
+Click on an item to see more detail or
+click> to see the full index.
+BIG>>
 
 
-
+ alt="flowchart">
 
 
 




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