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Update flowchart and backend descriptions.

This commit is contained in:
Bruce Momjian 1998-06-28 15:00:28 +00:00
parent 0cba552301
commit 8986e609ab
1 changed files with 27 additions and 21 deletions
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48
src/tools/backend/index.html
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@ -32,35 +32,35 @@ The parser takes the complex queries, 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
WHERE clause qualification, which is filled in by
<A HREF="../../backend/parser/parse_clause.c">transformWhereClause().</A>
Each table is represented by a <A HREF="../../include/nodes/parsenodes.h">
RangeTableEntry,</A>
and they are linked together to form the <I>range table</I> for the
query, and is generated by <A HREF="../../backend/parser/parse_clause.c">
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.
<P>
Certain queries, like SELECT, return columns of data. Other queries,
like INSERT and UPDATE, specify the columns modified by the query.
These columns references are converted to <A
These column references are converted to <A
HREF="../../include/nodes/primnodes.h"> Resdom</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, and is generated by
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(SUM()), GROUP BY, ORDER BY are
also stored in their own fields.
also stored in their own Query fields.
<P>
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 <A
HREF="../../backend/rewrite">rewrite</A> system.
<P>
The optimizer takes the Query structure, and generates an optimal
<A HREF="../..//include/nodes/plannodes.h">Plan</A> containing primitive
operations to be performed by the executor to complete the query. The
<A HREF="../../backend/optimizer/path">path</A> module
determines the table join order and join type of each of the tables in
the RangeTable, using Query.qual(WHERE clause) to consider optimal index
The <A HREF="../../backend/optimizer">optimizer</A> takes the Query
structure, and generates an optimal
<A HREF="../..//include/nodes/plannodes.h">Plan</A> containing the
primitive operations to be performed by the executor 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(WHERE clause) to consider optimal index
usage.
<P>
The Plan is then passed to the <A
@ -76,21 +76,27 @@ table data/index blocks, locks, and backend information:
<LI>ShmemIndex - contains an index of all other shared memory
structures, allowing quick lookup of other structure locations in shared
memory
<LI>Buffer Descriptors - control header for shared memory buffer block
<LI>Buffer Blocks - block of table/index data shared by all backends
<LI><A HREF="../../include/storage/buf_internals.h">Buffer
Descriptors</A> - control header for shared memory buffer block
<LI><A HREF="../../include/storage/buf_internals.h">Buffer Blocks</A>
- block of table/index data shared by all backends
<LI>Shared Buf Lookup Table - lookup to see if a requested buffer
is already in the shared memory area
<LI>LockTable - lock table structure, specifiying table, lock types, and
<LI><A HREF="../../include/storage/lock.h">LockTable</A>
- lock table structure, specifiying table, lock types, and
backends holding or waiting on lock
<LI>LockTable (lock hash) - lookup of LockTable structures using
table name
<LI>LockTable (xid hash) - lookup of LockTable structures using
transaction id
<LI>Proc Header - information about each backend, including locks held/waiting,
indexed by process id
<LI><A HREF="../../include/storage/proc.h">Proc Header</A> - information
about each backend, including locks held/waiting, indexed by process id
</UL>
Each structure is created by calling <A
HREF="../../backend/storage/ipc/shmem.c"> ShmemInitStruct().</A>
Each data structure is created by calling <A
HREF="../../backend/storage/ipc/shmem.c"> ShmemInitStruct(),</A> and
the lookup hashes are created by
<A HREF="../../backend/storage/ipc/shmem.c">ShmemInitHash().</A>
<HR>
<CENTER>
<EM><BIG>