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Revise TupleTableSlot code to avoid unnecessary construction and disassembly

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of tuples when passing data up through multiple plan nodes.  A slot can now
hold either a normal "physical" HeapTuple, or a "virtual" tuple consisting
of Datum/isnull arrays.  Upper plan levels can usually just copy the Datum
arrays, avoiding heap_formtuple() and possible subsequent nocachegetattr()
calls to extract the data again.  This work extends Atsushi Ogawa's earlier
patch, which provided the key idea of adding Datum arrays to TupleTableSlots.
(I believe however that something like this was foreseen way back in Berkeley
days --- see the old comment on ExecProject.)  A test case involving many
levels of join of fairly wide tables (about 80 columns altogether) showed
about 3x overall speedup, though simple queries will probably not be
helped very much.

I have also duplicated some code in heaptuple.c in order to provide versions
of heap_formtuple and friends that use "bool" arrays to indicate null
attributes, instead of the old convention of "char" arrays containing either
'n' or ' '.  This provides a better match to the convention used by
ExecEvalExpr.  While I have not made a concerted effort to get rid of uses
of the old routines, I think they should be deprecated and eventually removed.
This commit is contained in:
Tom Lane
2005-03-16 21:38:10 +00:00
parent 712f053587
commit f97aebd162
44 changed files with 1766 additions and 934 deletions
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8
doc/src/sgml/xfunc.sgml
View File

@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.100 2005/03/12 20:25:06 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.101 2005/03/16 21:38:04 tgl Exp $
-->
<sect1 id="xfunc">
@ -2219,7 +2219,7 @@ CREATE FUNCTION c_overpaid(emp, integer) RETURNS boolean
case, you first need to obtain or construct a <structname>TupleDesc</>
descriptor for the tuple structure. When working with Datums, you
pass the <structname>TupleDesc</> to <function>BlessTupleDesc</>,
and then call <function>heap_formtuple</> for each row. When working
and then call <function>heap_form_tuple</> for each row. When working
with C strings, you pass the <structname>TupleDesc</> to
<function>TupleDescGetAttInMetadata</>, and then call
<function>BuildTupleFromCStrings</> for each row. In the case of a
@ -2264,7 +2264,7 @@ AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc)
<para>
When working with Datums, use
<programlisting>
HeapTuple heap_formtuple(TupleDesc tupdesc, Datum *values, char *nulls)
HeapTuple heap_form_tuple(TupleDesc tupdesc, Datum *values, bool *isnull)
</programlisting>
to build a <structname>HeapTuple</> given user data in Datum form.
</para>
@ -2383,7 +2383,7 @@ typedef struct
*
* tuple_desc is for use when returning tuples (i.e. composite data types)
* and is only needed if you are going to build the tuples with
* heap_formtuple() rather than with BuildTupleFromCStrings(). Note that
* heap_form_tuple() rather than with BuildTupleFromCStrings(). Note that
* the TupleDesc pointer stored here should usually have been run through
* BlessTupleDesc() first.
*/