/*
* systable_beginscan_ordered --- set up for ordered catalog scan
*
* These routines have essentially the same API as systable_beginscan etc,
* except that they guarantee to return multiple matching tuples in
* index order. Also, for largely historical reasons, the index to use
* is opened and locked by the caller, not here.
*
* Currently we do not support non-index-based scans here. (In principle
* we could do a heapscan and sort, but the uses are in places that
* probably don't need to still work with corrupted catalog indexes.)
* For the moment, therefore, these functions are merely the thinnest of
* wrappers around index_beginscan/index_getnext. The main reason for their
* existence is to centralize possible future support of lossy operators
* in catalog scans.
*/
SysScanDesc
systable_beginscan_ordered(Relation heapRelation,
Relation indexRelation,
Snapshot snapshot,
int nkeys, ScanKey key)
{
SysScanDesc sysscan;
int i;
/* REINDEX can probably be a hard error here ... */
if (ReindexIsProcessingIndex(RelationGetRelid(indexRelation)))
elog(ERROR, "cannot do ordered scan on index \"%s\", because it is being reindexed",
RelationGetRelationName(indexRelation));
/* ... but we only throw a warning about violating IgnoreSystemIndexes */
if (IgnoreSystemIndexes)
elog(WARNING, "using index \"%s\" despite IgnoreSystemIndexes",
RelationGetRelationName(indexRelation));
sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
sysscan->heap_rel = heapRelation;
sysscan->irel = indexRelation;
if (snapshot == NULL)
{
Oid relid = RelationGetRelid(heapRelation);
snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
sysscan->snapshot = snapshot;
}
else
{
/* Caller is responsible for any snapshot. */
sysscan->snapshot = NULL;
}
/* Change attribute numbers to be index column numbers. */
for (i = 0; i < nkeys; i++)
{
int j;
for (j = 0; j < indexRelation->rd_index->indnatts; j++)
{
if (key[i].sk_attno == indexRelation->rd_index->indkey.values[j])
{
key[i].sk_attno = j + 1;
break;
}
}
if (j == indexRelation->rd_index->indnatts)
elog(ERROR, "column is not in index");
}
sysscan->iscan = index_beginscan(heapRelation, indexRelation,
snapshot, nkeys, 0);
index_rescan(sysscan->iscan, key, nkeys, NULL, 0);
sysscan->scan = NULL;
return sysscan;
}
/*
* systable_beginscan --- set up for heap-or-index scan
*
* rel: catalog to scan, already opened and suitably locked
* indexRelname: name of index to conditionally use
* indexOK: if false, forces a heap scan (see notes below)
* snapshot: time qual to use (usually should be SnapshotNow)
* nkeys, key: scan keys
*
* The attribute numbers in the scan key should be set for the heap case.
* If we choose to index, we reset them to 1..n to reference the index
* columns. Note this means there must be one scankey qualification per
* index column! This is checked by the Asserts in the normal, index-using
* case, but won't be checked if the heapscan path is taken.
*
* The routine checks the normal cases for whether an indexscan is safe,
* but caller can make additional checks and pass indexOK=false if needed.
* In standard case indexOK can simply be constant TRUE.
*/
SysScanDesc
systable_beginscan(Relation heapRelation,
const char *indexRelname,
bool indexOK,
Snapshot snapshot,
int nkeys, ScanKey key)
{
SysScanDesc sysscan;
Relation irel;
if (indexOK && !IsIgnoringSystemIndexes())
{
/* We assume it's a system index, so index_openr is OK */
irel = index_openr(indexRelname);
if (ReindexIsProcessingIndex(RelationGetRelid(irel)))
{
/* oops, can't use index that's being rebuilt */
index_close(irel);
irel = NULL;
}
}
else
irel = NULL;
sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
sysscan->heap_rel = heapRelation;
sysscan->irel = irel;
if (irel)
{
int i;
/*
* Change attribute numbers to be index column numbers.
*
* This code could be generalized to search for the index key numbers
* to substitute, but for now there's no need.
*/
for (i = 0; i < nkeys; i++)
{
Assert(key[i].sk_attno == irel->rd_index->indkey[i]);
key[i].sk_attno = i + 1;
}
sysscan->iscan = index_beginscan(heapRelation, irel, snapshot,
nkeys, key);
sysscan->scan = NULL;
}
else
{
sysscan->scan = heap_beginscan(heapRelation, snapshot, nkeys, key);
sysscan->iscan = NULL;
}
return sysscan;
}
/*
* systable_beginscan --- set up for heap-or-index scan
*
* rel: catalog to scan, already opened and suitably locked
* indexId: OID of index to conditionally use
* indexOK: if false, forces a heap scan (see notes below)
* snapshot: time qual to use (usually should be SnapshotNow)
* nkeys, key: scan keys
*
* The attribute numbers in the scan key should be set for the heap case.
* If we choose to index, we reset them to 1..n to reference the index
* columns. Note this means there must be one scankey qualification per
* index column! This is checked by the Asserts in the normal, index-using
* case, but won't be checked if the heapscan path is taken.
*
* The routine checks the normal cases for whether an indexscan is safe,
* but caller can make additional checks and pass indexOK=false if needed.
* In standard case indexOK can simply be constant TRUE.
*/
SysScanDesc
systable_beginscan(Relation heapRelation,
Oid indexId,
bool indexOK,
Snapshot snapshot,
int nkeys, ScanKey key)
{
SysScanDesc sysscan;
Relation irel;
if (indexOK &&
!IgnoreSystemIndexes &&
!ReindexIsProcessingIndex(indexId))
irel = index_open(indexId, AccessShareLock);
else
irel = NULL;
sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
sysscan->heap_rel = heapRelation;
sysscan->irel = irel;
if (irel)
{
int i;
/* Change attribute numbers to be index column numbers. */
for (i = 0; i < nkeys; i++)
{
int j;
for (j = 0; j < irel->rd_index->indnatts; j++)
{
if (key[i].sk_attno == irel->rd_index->indkey.values[j])
{
key[i].sk_attno = j + 1;
break;
}
}
if (j == irel->rd_index->indnatts)
elog(ERROR, "column is not in index");
}
sysscan->iscan = index_beginscan(heapRelation, irel,
snapshot, nkeys, key);
sysscan->scan = NULL;
}
else
{
sysscan->scan = heap_beginscan(heapRelation, snapshot, nkeys, key);
sysscan->iscan = NULL;
}
return sysscan;
}
/*
* systable_beginscan --- set up for heap-or-index scan
*
* rel: catalog to scan, already opened and suitably locked
* indexId: OID of index to conditionally use
* indexOK: if false, forces a heap scan (see notes below)
* snapshot: time qual to use (usually should be SnapshotNow)
* nkeys, key: scan keys
*
* The attribute numbers in the scan key should be set for the heap case.
* If we choose to index, we reset them to 1..n to reference the index
* columns. Note this means there must be one scankey qualification per
* index column! This is checked by the Asserts in the normal, index-using
* case, but won't be checked if the heapscan path is taken.
*
* The routine checks the normal cases for whether an indexscan is safe,
* but caller can make additional checks and pass indexOK=false if needed.
* In standard case indexOK can simply be constant TRUE.
*/
SysScanDesc
systable_beginscan(Relation heapRelation,
Oid indexId,
bool indexOK,
Snapshot snapshot,
int nkeys, ScanKey key)
{
SysScanDesc sysscan;
Relation irel;
if (indexOK &&
!IgnoreSystemIndexes &&
!ReindexIsProcessingIndex(indexId))
irel = index_open(indexId, AccessShareLock);
else
irel = NULL;
sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
sysscan->heap_rel = heapRelation;
sysscan->irel = irel;
if (irel)
{
int i;
/*
* Change attribute numbers to be index column numbers.
*
* This code could be generalized to search for the index key numbers
* to substitute, but for now there's no need.
*/
for (i = 0; i < nkeys; i++)
{
Assert(key[i].sk_attno == irel->rd_index->indkey.values[i]);
key[i].sk_attno = i + 1;
}
sysscan->iscan = index_beginscan(heapRelation, irel,
snapshot, nkeys, key);
sysscan->scan = NULL;
}
else
{
sysscan->scan = heap_beginscan(heapRelation, snapshot, nkeys, key);
sysscan->iscan = NULL;
}
return sysscan;
}
/*
* systable_beginscan --- set up for heap-or-index scan
*
* rel: catalog to scan, already opened and suitably locked
* indexId: OID of index to conditionally use
* indexOK: if false, forces a heap scan (see notes below)
* snapshot: time qual to use (NULL for a recent catalog snapshot)
* nkeys, key: scan keys
*
* The attribute numbers in the scan key should be set for the heap case.
* If we choose to index, we reset them to 1..n to reference the index
* columns. Note this means there must be one scankey qualification per
* index column! This is checked by the Asserts in the normal, index-using
* case, but won't be checked if the heapscan path is taken.
*
* The routine checks the normal cases for whether an indexscan is safe,
* but caller can make additional checks and pass indexOK=false if needed.
* In standard case indexOK can simply be constant TRUE.
*/
SysScanDesc
systable_beginscan(Relation heapRelation,
Oid indexId,
bool indexOK,
Snapshot snapshot,
int nkeys, ScanKey key)
{
SysScanDesc sysscan;
Relation irel;
if (indexOK &&
!IgnoreSystemIndexes &&
!ReindexIsProcessingIndex(indexId))
irel = index_open(indexId, AccessShareLock);
else
irel = NULL;
sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
sysscan->heap_rel = heapRelation;
sysscan->irel = irel;
if (snapshot == NULL)
{
Oid relid = RelationGetRelid(heapRelation);
snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
sysscan->snapshot = snapshot;
}
else
{
/* Caller is responsible for any snapshot. */
sysscan->snapshot = NULL;
}
if (irel)
{
int i;
/* Change attribute numbers to be index column numbers. */
for (i = 0; i < nkeys; i++)
{
int j;
for (j = 0; j < irel->rd_index->indnatts; j++)
{
if (key[i].sk_attno == irel->rd_index->indkey.values[j])
{
key[i].sk_attno = j + 1;
break;
}
}
if (j == irel->rd_index->indnatts)
elog(ERROR, "column is not in index");
}
sysscan->iscan = index_beginscan(heapRelation, irel,
snapshot, nkeys, 0);
index_rescan(sysscan->iscan, key, nkeys, NULL, 0);
sysscan->scan = NULL;
}
else
{
/*
* We disallow synchronized scans when forced to use a heapscan on a
* catalog. In most cases the desired rows are near the front, so
* that the unpredictable start point of a syncscan is a serious
* disadvantage; and there are no compensating advantages, because
* it's unlikely that such scans will occur in parallel.
*/
sysscan->scan = heap_beginscan_strat(heapRelation, snapshot,
nkeys, key,
true, false);
sysscan->iscan = NULL;
}
return sysscan;
}
