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Update flowchart and backend descriptions.
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‎src/tools/backend/index.html

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@@ -32,35 +32,35 @@ <H2 ALIGN=CENTER>
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<A HREF="../../include/nodes/parsenodes.h">Query</A> structure that
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contains all the elements used by complex queries. Query.qual holds the
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WHERE clause qualification, which is filled in by
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<A HREF="../../backend/parser/parse_clause.c">transformWhereClause().</A>
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Each table is represented by a <A HREF="../../include/nodes/parsenodes.h">
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RangeTableEntry,</A>
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and they are linked together to form the <I>range table</I> for the
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query, and is generated by <A HREF="../../backend/parser/parse_clause.c">
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Each table referenced in the query is represented by a <A
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HREF="../../include/nodes/parsenodes.h"> RangeTableEntry,</A> and they
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are linked together to form the <I>range table</I> of the query, which is
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generated by <A HREF="../../backend/parser/parse_clause.c">
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makeRangeTable().</A> Query.rtable holds the queries range table.
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<P>
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Certain queries, like SELECT, return columns of data. Other queries,
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like INSERT and UPDATE, specify the columns modified by the query.
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These columns references are converted to <A
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These column references are converted to <A
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HREF="../../include/nodes/primnodes.h"> Resdom</A> entries, which are
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linked together to make up the <I>target list</I> of the query. The
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target list is stored in Query.targetList, and is generated by
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target list is stored in Query.targetList, which is generated by
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<A HREF="../../backend/parser/parse_target.c">transformTargetList().</A>
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<P>
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Other query elements, like aggregates(SUM()), GROUP BY, ORDER BY are
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also stored in their own fields.
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also stored in their own Query fields.
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<P>
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The next step is for the Query to be modified by any VIEWS or RULES that
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may apply to the query. This is performed by the <A
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HREF="../../backend/rewrite">rewrite</A> system.
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<P>
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The optimizer takes the Query structure, and generates an optimal
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<A HREF="../..//include/nodes/plannodes.h">Plan</A> containing primitive
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operations to be performed by the executor to complete the query. The
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<A HREF="../../backend/optimizer/path">path</A> module
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determines the table join order and join type of each of the tables in
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the RangeTable, using Query.qual(WHERE clause) to consider optimal index
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The <A HREF="../../backend/optimizer">optimizer</A> takes the Query
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structure, and generates an optimal
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<A HREF="../..//include/nodes/plannodes.h">Plan</A> containing the
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primitive operations to be performed by the executor to execute the
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query. The <A HREF="../../backend/optimizer/path">path</A> module
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determines the best table join order and join type of each table in the
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RangeTable, using Query.qual(WHERE clause) to consider optimal index
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usage.
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<P>
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The Plan is then passed to the <A
@@ -76,21 +76,27 @@ <H2 ALIGN=CENTER>
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<LI>ShmemIndex - contains an index of all other shared memory
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structures, allowing quick lookup of other structure locations in shared
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memory
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<LI>Buffer Descriptors - control header for shared memory buffer block
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<LI>Buffer Blocks - block of table/index data shared by all backends
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<LI><A HREF="../../include/storage/buf_internals.h">Buffer
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Descriptors</A> - control header for shared memory buffer block
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<LI><A HREF="../../include/storage/buf_internals.h">Buffer Blocks</A>
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- block of table/index data shared by all backends
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<LI>Shared Buf Lookup Table - lookup to see if a requested buffer
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is already in the shared memory area
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<LI>LockTable - lock table structure, specifiying table, lock types, and
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<LI><A HREF="../../include/storage/lock.h">LockTable</A>
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- lock table structure, specifiying table, lock types, and
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backends holding or waiting on lock
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<LI>LockTable (lock hash) - lookup of LockTable structures using
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table name
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<LI>LockTable (xid hash) - lookup of LockTable structures using
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transaction id
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<LI>Proc Header - information about each backend, including locks held/waiting,
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indexed by process id
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<LI><A HREF="../../include/storage/proc.h">Proc Header</A> - information
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about each backend, including locks held/waiting, indexed by process id
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</UL>
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Each structure is created by calling <A
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HREF="../../backend/storage/ipc/shmem.c"> ShmemInitStruct().</A>
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Each data structure is created by calling <A
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HREF="../../backend/storage/ipc/shmem.c"> ShmemInitStruct(),</A> and
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the lookup hashes are created by
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<A HREF="../../backend/storage/ipc/shmem.c">ShmemInitHash().</A>
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<HR>
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<CENTER>
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<EM><BIG>

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