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Improve comments about btree's use of ScanKey data structures: there

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are two basically different kinds of scankeys, and we ought to try harder
to indicate which is used in each place in the code.  I've chosen the names
"search scankey" and "insertion scankey", though you could make about
as good an argument for "operator scankey" and "comparison function
scankey".
This commit is contained in:
Tom Lane
2006-01-17 00:09:01 +00:00
parent e38217d1ec
commit 73e3566078
5 changed files with 78 additions and 47 deletions
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17
src/backend/access/nbtree/nbtutils.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.67 2005/12/07 19:37:53 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.68 2006/01/17 00:09:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -23,7 +23,7 @@
/*
* _bt_mkscankey
* Build a scan key that contains comparison data from itup
* Build an insertion scan key that contains comparison data from itup
* as well as comparator routines appropriate to the key datatypes.
*
* The result is intended for use with _bt_compare().
@ -67,11 +67,12 @@ _bt_mkscankey(Relation rel, IndexTuple itup)
/*
* _bt_mkscankey_nodata
* Build a scan key that contains comparator routines appropriate to
* the key datatypes, but no comparison data. The comparison data
* ultimately used must match the key datatypes.
* Build an insertion scan key that contains 3-way comparator routines
* appropriate to the key datatypes, but no comparison data. The
* comparison data ultimately used must match the key datatypes.
*
* The result cannot be used with _bt_compare(). Currently this
* The result cannot be used with _bt_compare(), unless comparison
* data is first stored into the key entries. Currently this
* routine is only called by nbtsort.c and tuplesort.c, which have
* their own comparison routines.
*/
@ -160,7 +161,7 @@ _bt_formitem(IndexTuple itup)
/*----------
* _bt_preprocess_keys() -- Preprocess scan keys
*
* The caller-supplied keys (in scan->keyData[]) are copied to
* The caller-supplied search-type keys (in scan->keyData[]) are copied to
* so->keyData[] with possible transformation. scan->numberOfKeys is
* the number of input keys, so->numberOfKeys gets the number of output
* keys (possibly less, never greater).
@ -485,7 +486,7 @@ _bt_preprocess_keys(IndexScanDesc scan)
* accordingly. See comments for _bt_preprocess_keys(), above, about how
* this is done.
*
* scan: index scan descriptor
* scan: index scan descriptor (containing a search-type scankey)
* page: buffer page containing index tuple
* offnum: offset number of index tuple (must be a valid item!)
* dir: direction we are scanning in