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Refactor nbtree insertion scankeys.

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Use dedicated struct to represent nbtree insertion scan keys.  Having a
dedicated struct makes the difference between search type scankeys and
insertion scankeys a lot clearer, and simplifies the signature of
several related functions.  This is based on a suggestion by Andrey
Lepikhov.

Streamline how unique index insertions cache binary search progress.
Cache the state of in-progress binary searches within _bt_check_unique()
for later instead of having callers avoid repeating the binary search in
an ad-hoc manner.  This makes it easy to add a new optimization:
_bt_check_unique() now falls out of its loop immediately in the common
case where it's already clear that there couldn't possibly be a
duplicate.

The new _bt_check_unique() scheme makes it a lot easier to manage cached
binary search effort afterwards, from within _bt_findinsertloc().  This
is needed for the upcoming patch to make nbtree tuples unique by
treating heap TID as a final tiebreaker column.  Unique key binary
searches need to restore lower and upper bounds.  They cannot simply
continue to use the >= lower bound as the offset to insert at, because
the heap TID tiebreaker column must be used in comparisons for the
restored binary search (unlike the original _bt_check_unique() binary
search, where scankey's heap TID column must be omitted).

Author: Peter Geoghegan, Heikki Linnakangas
Reviewed-By: Heikki Linnakangas, Andrey Lepikhov
Discussion: https://postgr.es/m/CAH2-WzmE6AhUdk9NdWBf4K3HjWXZBX3+umC7mH7+WDrKcRtsOw@mail.gmail.com
This commit is contained in:
Peter Geoghegan
2019-03-20 09:30:57 -07:00
parent 550b9d26f8
commit e5adcb789d
9 changed files with 532 additions and 390 deletions
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96
src/backend/access/nbtree/nbtutils.c
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@ -56,34 +56,37 @@ static bool _bt_check_rowcompare(ScanKey skey,
* 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().
* Result is intended for use with _bt_compare(). Callers that don't
* need to fill out the insertion scankey arguments (e.g. they use an
* ad-hoc comparison routine) can pass a NULL index tuple.
*/
ScanKey
BTScanInsert
_bt_mkscankey(Relation rel, IndexTuple itup)
{
BTScanInsert key;
ScanKey skey;
TupleDesc itupdesc;
int indnatts PG_USED_FOR_ASSERTS_ONLY;
int indnkeyatts;
int16 *indoption;
int tupnatts;
int i;
itupdesc = RelationGetDescr(rel);
indnatts = IndexRelationGetNumberOfAttributes(rel);
indnkeyatts = IndexRelationGetNumberOfKeyAttributes(rel);
indoption = rel->rd_indoption;
tupnatts = itup ? BTreeTupleGetNAtts(itup, rel) : 0;
Assert(indnkeyatts > 0);
Assert(indnkeyatts <= indnatts);
Assert(BTreeTupleGetNAtts(itup, rel) == indnatts ||
BTreeTupleGetNAtts(itup, rel) == indnkeyatts);
Assert(tupnatts <= IndexRelationGetNumberOfAttributes(rel));
/*
* We'll execute search using scan key constructed on key columns. Non-key
* (INCLUDE index) columns are always omitted from scan keys.
*/
skey = (ScanKey) palloc(indnkeyatts * sizeof(ScanKeyData));
key = palloc(offsetof(BTScanInsertData, scankeys) +
sizeof(ScanKeyData) * indnkeyatts);
key->nextkey = false;
key->keysz = Min(indnkeyatts, tupnatts);
skey = key->scankeys;
for (i = 0; i < indnkeyatts; i++)
{
FmgrInfo *procinfo;
@ -96,7 +99,19 @@ _bt_mkscankey(Relation rel, IndexTuple itup)
* comparison can be needed.
*/
procinfo = index_getprocinfo(rel, i + 1, BTORDER_PROC);
arg = index_getattr(itup, i + 1, itupdesc, &null);
/*
* Key arguments built when caller provides no tuple are
* defensively represented as NULL values. They should never be
* used.
*/
if (i < tupnatts)
arg = index_getattr(itup, i + 1, itupdesc, &null);
else
{
arg = (Datum) 0;
null = true;
}
flags = (null ? SK_ISNULL : 0) | (indoption[i] << SK_BT_INDOPTION_SHIFT);
ScanKeyEntryInitializeWithInfo(&skey[i],
flags,
@ -108,64 +123,7 @@ _bt_mkscankey(Relation rel, IndexTuple itup)
arg);
}
return skey;
}
/*
* _bt_mkscankey_nodata
* 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(), 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.
*/
ScanKey
_bt_mkscankey_nodata(Relation rel)
{
ScanKey skey;
int indnkeyatts;
int16 *indoption;
int i;
indnkeyatts = IndexRelationGetNumberOfKeyAttributes(rel);
indoption = rel->rd_indoption;
skey = (ScanKey) palloc(indnkeyatts * sizeof(ScanKeyData));
for (i = 0; i < indnkeyatts; i++)
{
FmgrInfo *procinfo;
int flags;
/*
* We can use the cached (default) support procs since no cross-type
* comparison can be needed.
*/
procinfo = index_getprocinfo(rel, i + 1, BTORDER_PROC);
flags = SK_ISNULL | (indoption[i] << SK_BT_INDOPTION_SHIFT);
ScanKeyEntryInitializeWithInfo(&skey[i],
flags,
(AttrNumber) (i + 1),
InvalidStrategy,
InvalidOid,
rel->rd_indcollation[i],
procinfo,
(Datum) 0);
}
return skey;
}
/*
* free a scan key made by either _bt_mkscankey or _bt_mkscankey_nodata.
*/
void
_bt_freeskey(ScanKey skey)
{
pfree(skey);
return key;
}
/*