/*
* get_op_hash_function
* Get the OID of the datatype-specific hash function associated with
* a hashable equality operator.
*
* Returns InvalidOid if no hash function can be found. (This indicates
* that the operator should not have been marked oprcanhash.)
*/
Oid
get_op_hash_function(Oid opno)
{
CatCList *catlist;
int i;
Oid opclass = InvalidOid;
/*
* Search pg_amop to see if the target operator is registered as the "="
* operator of any hash opclass. If the operator is registered in
* multiple opclasses, assume we can use the associated hash function from
* any one.
*/
catlist = SearchSysCacheList(AMOPOPID, 1,
ObjectIdGetDatum(opno),
0, 0, 0);
for (i = 0; i < catlist->n_members; i++)
{
HeapTuple tuple = &catlist->members[i]->tuple;
Form_pg_amop aform = (Form_pg_amop) GETSTRUCT(tuple);
if (aform->amopstrategy == HTEqualStrategyNumber &&
opclass_is_hash(aform->amopclaid))
{
opclass = aform->amopclaid;
break;
}
}
ReleaseSysCacheList(catlist);
if (OidIsValid(opclass))
{
/* Found a suitable opclass, get its default hash support function */
return get_opclass_proc(opclass, InvalidOid, HASHPROC);
}
/* Didn't find a match... */
return InvalidOid;
}
/*
* _bt_first() -- Find the first item in a scan.
*
* We need to be clever about the direction of scan, the search
* conditions, and the tree ordering. We find the first item (or,
* if backwards scan, the last item) in the tree that satisfies the
* qualifications in the scan key. On success exit, the page containing
* the current index tuple is pinned but not locked, and data about
* the matching tuple(s) on the page has been loaded into so->currPos,
* and scan->xs_ctup.t_self is set to the heap TID of the current tuple.
*
* If there are no matching items in the index, we return FALSE, with no
* pins or locks held.
*
* Note that scan->keyData[], and the so->keyData[] scankey built from it,
* are both search-type scankeys (see nbtree/README for more about this).
* Within this routine, we build a temporary insertion-type scankey to use
* in locating the scan start position.
*/
bool
_bt_first(IndexScanDesc scan, ScanDirection dir)
{
Relation rel = scan->indexRelation;
BTScanOpaque so = (BTScanOpaque) scan->opaque;
Buffer buf;
BTStack stack;
OffsetNumber offnum;
StrategyNumber strat;
bool nextkey;
bool goback;
ScanKey startKeys[INDEX_MAX_KEYS];
ScanKeyData scankeys[INDEX_MAX_KEYS];
int keysCount = 0;
int i;
StrategyNumber strat_total;
pgstat_count_index_scan(&scan->xs_pgstat_info);
/*
* Examine the scan keys and eliminate any redundant keys; also mark the
* keys that must be matched to continue the scan.
*/
_bt_preprocess_keys(scan);
/*
* Quit now if _bt_preprocess_keys() discovered that the scan keys can
* never be satisfied (eg, x == 1 AND x > 2).
*/
if (!so->qual_ok)
return false;
/*----------
* Examine the scan keys to discover where we need to start the scan.
*
* We want to identify the keys that can be used as starting boundaries;
* these are =, >, or >= keys for a forward scan or =, <, <= keys for
* a backwards scan. We can use keys for multiple attributes so long as
* the prior attributes had only =, >= (resp. =, <=) keys. Once we accept
* a > or < boundary or find an attribute with no boundary (which can be
* thought of as the same as "> -infinity"), we can't use keys for any
* attributes to its right, because it would break our simplistic notion
* of what initial positioning strategy to use.
*
* When the scan keys include non-default operators, _bt_preprocess_keys
* may not be able to eliminate redundant keys; in such cases we will
* arbitrarily pick a usable one for each attribute. This is correct
* but possibly not optimal behavior. (For example, with keys like
* "x >= 4 AND x >= 5" we would elect to scan starting at x=4 when
* x=5 would be more efficient.) Since the situation only arises in
* hokily-worded queries, live with it.
*
* When both equality and inequality keys appear for a single attribute
* (again, only possible when non-default operators appear), we *must*
* select one of the equality keys for the starting point, because
* _bt_checkkeys() will stop the scan as soon as an equality qual fails.
* For example, if we have keys like "x >= 4 AND x = 10" and we elect to
* start at x=4, we will fail and stop before reaching x=10. If multiple
* equality quals survive preprocessing, however, it doesn't matter which
* one we use --- by definition, they are either redundant or
* contradictory.
*
* In this loop, row-comparison keys are treated the same as keys on their
* first (leftmost) columns. We'll add on lower-order columns of the row
* comparison below, if possible.
*
* The selected scan keys (at most one per index column) are remembered by
* storing their addresses into the local startKeys[] array.
*----------
*/
strat_total = BTEqualStrategyNumber;
if (so->numberOfKeys > 0)
{
AttrNumber curattr;
ScanKey chosen;
ScanKey cur;
/*
* chosen is the so-far-chosen key for the current attribute, if any.
* We don't cast the decision in stone until we reach keys for the
* next attribute.
*/
curattr = 1;
chosen = NULL;
/*
* Loop iterates from 0 to numberOfKeys inclusive; we use the last
* pass to handle after-last-key processing. Actual exit from the
* loop is at one of the "break" statements below.
*/
for (cur = so->keyData, i = 0;; cur++, i++)
{
if (i >= so->numberOfKeys || cur->sk_attno != curattr)
{
/*
* Done looking at keys for curattr. If we didn't find a
* usable boundary key, quit; else save the boundary key
* pointer in startKeys.
*/
if (chosen == NULL)
break;
startKeys[keysCount++] = chosen;
/*
* Adjust strat_total, and quit if we have stored a > or <
* key.
*/
strat = chosen->sk_strategy;
if (strat != BTEqualStrategyNumber)
{
strat_total = strat;
if (strat == BTGreaterStrategyNumber ||
strat == BTLessStrategyNumber)
break;
}
/*
* Done if that was the last attribute, or if next key is not
* in sequence (implying no boundary key is available for the
* next attribute).
*/
if (i >= so->numberOfKeys ||
cur->sk_attno != curattr + 1)
break;
/*
* Reset for next attr.
*/
curattr = cur->sk_attno;
chosen = NULL;
}
/* Can we use this key as a starting boundary for this attr? */
switch (cur->sk_strategy)
{
case BTLessStrategyNumber:
case BTLessEqualStrategyNumber:
if (chosen == NULL && ScanDirectionIsBackward(dir))
chosen = cur;
break;
case BTEqualStrategyNumber:
/* override any non-equality choice */
chosen = cur;
break;
case BTGreaterEqualStrategyNumber:
case BTGreaterStrategyNumber:
if (chosen == NULL && ScanDirectionIsForward(dir))
chosen = cur;
break;
}
}
}
/*
* If we found no usable boundary keys, we have to start from one end of
* the tree. Walk down that edge to the first or last key, and scan from
* there.
*/
if (keysCount == 0)
return _bt_endpoint(scan, dir);
/*
* We want to start the scan somewhere within the index. Set up an
* insertion scankey we can use to search for the boundary point we
* identified above. The insertion scankey is built in the local
* scankeys[] array, using the keys identified by startKeys[].
*/
Assert(keysCount <= INDEX_MAX_KEYS);
for (i = 0; i < keysCount; i++)
{
ScanKey cur = startKeys[i];
Assert(cur->sk_attno == i + 1);
if (cur->sk_flags & SK_ROW_HEADER)
{
/*
* Row comparison header: look to the first row member instead.
*
* The member scankeys are already in insertion format (ie, they
* have sk_func = 3-way-comparison function), but we have to watch
* out for nulls, which _bt_preprocess_keys didn't check. A null
* in the first row member makes the condition unmatchable, just
* like qual_ok = false.
*/
ScanKey subkey = (ScanKey) DatumGetPointer(cur->sk_argument);
Assert(subkey->sk_flags & SK_ROW_MEMBER);
if (subkey->sk_flags & SK_ISNULL)
return false;
memcpy(scankeys + i, subkey, sizeof(ScanKeyData));
/*
* If the row comparison is the last positioning key we accepted,
* try to add additional keys from the lower-order row members.
* (If we accepted independent conditions on additional index
* columns, we use those instead --- doesn't seem worth trying to
* determine which is more restrictive.) Note that this is OK
* even if the row comparison is of ">" or "<" type, because the
* condition applied to all but the last row member is effectively
* ">=" or "<=", and so the extra keys don't break the positioning
* scheme. But, by the same token, if we aren't able to use all
* the row members, then the part of the row comparison that we
* did use has to be treated as just a ">=" or "<=" condition,
* and so we'd better adjust strat_total accordingly.
*/
if (i == keysCount - 1)
{
bool used_all_subkeys = false;
Assert(!(subkey->sk_flags & SK_ROW_END));
for(;;)
{
subkey++;
Assert(subkey->sk_flags & SK_ROW_MEMBER);
if (subkey->sk_attno != keysCount + 1)
break; /* out-of-sequence, can't use it */
if (subkey->sk_strategy != cur->sk_strategy)
break; /* wrong direction, can't use it */
if (subkey->sk_flags & SK_ISNULL)
break; /* can't use null keys */
Assert(keysCount < INDEX_MAX_KEYS);
memcpy(scankeys + keysCount, subkey, sizeof(ScanKeyData));
keysCount++;
if (subkey->sk_flags & SK_ROW_END)
{
used_all_subkeys = true;
break;
}
}
if (!used_all_subkeys)
{
switch (strat_total)
{
case BTLessStrategyNumber:
strat_total = BTLessEqualStrategyNumber;
break;
case BTGreaterStrategyNumber:
strat_total = BTGreaterEqualStrategyNumber;
break;
}
}
break; /* done with outer loop */
}
}
else
{
/*
* Ordinary comparison key. Transform the search-style scan key
* to an insertion scan key by replacing the sk_func with the
* appropriate btree comparison function.
*
* If scankey operator is of default subtype, we can use the
* cached comparison function; otherwise gotta look it up in the
* catalogs.
*/
if (cur->sk_subtype == InvalidOid)
{
FmgrInfo *procinfo;
procinfo = index_getprocinfo(rel, cur->sk_attno, BTORDER_PROC);
ScanKeyEntryInitializeWithInfo(scankeys + i,
cur->sk_flags,
cur->sk_attno,
InvalidStrategy,
InvalidOid,
procinfo,
cur->sk_argument);
}
else
{
RegProcedure cmp_proc;
cmp_proc = get_opclass_proc(rel->rd_indclass->values[i],
cur->sk_subtype,
BTORDER_PROC);
ScanKeyEntryInitialize(scankeys + i,
cur->sk_flags,
cur->sk_attno,
InvalidStrategy,
cur->sk_subtype,
cmp_proc,
cur->sk_argument);
}
}
}
/*----------
* Examine the selected initial-positioning strategy to determine exactly
* where we need to start the scan, and set flag variables to control the
* code below.
*
* If nextkey = false, _bt_search and _bt_binsrch will locate the first
* item >= scan key. If nextkey = true, they will locate the first
* item > scan key.
*
* If goback = true, we will then step back one item, while if
* goback = false, we will start the scan on the located item.
*
* it's yet other place to add some code later for is(not)null ...
*----------
*/
switch (strat_total)
{
case BTLessStrategyNumber:
/*
* Find first item >= scankey, then back up one to arrive at last
* item < scankey. (Note: this positioning strategy is only used
* for a backward scan, so that is always the correct starting
* position.)
*/
nextkey = false;
goback = true;
break;
case BTLessEqualStrategyNumber:
/*
* Find first item > scankey, then back up one to arrive at last
* item <= scankey. (Note: this positioning strategy is only used
* for a backward scan, so that is always the correct starting
* position.)
*/
nextkey = true;
goback = true;
break;
case BTEqualStrategyNumber:
/*
* If a backward scan was specified, need to start with last equal
* item not first one.
*/
if (ScanDirectionIsBackward(dir))
{
/*
* This is the same as the <= strategy. We will check at the
* end whether the found item is actually =.
*/
nextkey = true;
goback = true;
}
else
{
/*
* This is the same as the >= strategy. We will check at the
* end whether the found item is actually =.
*/
nextkey = false;
goback = false;
}
break;
case BTGreaterEqualStrategyNumber:
/*
* Find first item >= scankey. (This is only used for forward
* scans.)
*/
nextkey = false;
goback = false;
break;
case BTGreaterStrategyNumber:
/*
* Find first item > scankey. (This is only used for forward
* scans.)
*/
nextkey = true;
goback = false;
break;
default:
/* can't get here, but keep compiler quiet */
elog(ERROR, "unrecognized strat_total: %d", (int) strat_total);
return false;
}
/*
* Use the manufactured insertion scan key to descend the tree and
* position ourselves on the target leaf page.
*/
stack = _bt_search(rel, keysCount, scankeys, nextkey, &buf, BT_READ);
/* don't need to keep the stack around... */
_bt_freestack(stack);
/* remember which buffer we have pinned, if any */
so->currPos.buf = buf;
if (!BufferIsValid(buf))
{
/* Only get here if index is completely empty */
return false;
}
/* initialize moreLeft/moreRight appropriately for scan direction */
if (ScanDirectionIsForward(dir))
{
so->currPos.moreLeft = false;
so->currPos.moreRight = true;
}
else
{
so->currPos.moreLeft = true;
so->currPos.moreRight = false;
}
so->numKilled = 0; /* just paranoia */
so->markItemIndex = -1; /* ditto */
/* position to the precise item on the page */
offnum = _bt_binsrch(rel, buf, keysCount, scankeys, nextkey);
/*
* If nextkey = false, we are positioned at the first item >= scan key, or
* possibly at the end of a page on which all the existing items are less
* than the scan key and we know that everything on later pages is greater
* than or equal to scan key.
*
* If nextkey = true, we are positioned at the first item > scan key, or
* possibly at the end of a page on which all the existing items are less
* than or equal to the scan key and we know that everything on later
* pages is greater than scan key.
*
* The actually desired starting point is either this item or the prior
* one, or in the end-of-page case it's the first item on the next page or
* the last item on this page. Adjust the starting offset if needed. (If
* this results in an offset before the first item or after the last one,
* _bt_readpage will report no items found, and then we'll step to the
* next page as needed.)
*/
if (goback)
offnum = OffsetNumberPrev(offnum);
/*
* Now load data from the first page of the scan.
*/
if (!_bt_readpage(scan, dir, offnum))
{
/*
* There's no actually-matching data on this page. Try to advance to
* the next page. Return false if there's no matching data at all.
*/
if (!_bt_steppage(scan, dir))
return false;
}
/* Drop the lock, but not pin, on the current page */
LockBuffer(so->currPos.buf, BUFFER_LOCK_UNLOCK);
/* OK, itemIndex says what to return */
scan->xs_ctup.t_self = so->currPos.items[so->currPos.itemIndex].heapTid;
return true;
}
/*
* lookup_type_cache
*
* Fetch the type cache entry for the specified datatype, and make sure that
* all the fields requested by bits in 'flags' are valid.
*
* The result is never NULL --- we will elog() if the passed type OID is
* invalid. Note however that we may fail to find one or more of the
* requested opclass-dependent fields; the caller needs to check whether
* the fields are InvalidOid or not.
*/
TypeCacheEntry *
lookup_type_cache(Oid type_id, int flags)
{
TypeCacheEntry *typentry;
bool found;
if (TypeCacheHash == NULL)
{
/* First time through: initialize the hash table */
HASHCTL ctl;
if (!CacheMemoryContext)
CreateCacheMemoryContext();
MemSet(&ctl, 0, sizeof(ctl));
ctl.keysize = sizeof(Oid);
ctl.entrysize = sizeof(TypeCacheEntry);
ctl.hash = tag_hash;
TypeCacheHash = hash_create("Type information cache", 64,
&ctl, HASH_ELEM | HASH_FUNCTION);
}
/* Try to look up an existing entry */
typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
(void *) &type_id,
HASH_FIND, NULL);
if (typentry == NULL)
{
/*
* If we didn't find one, we want to make one. But first get the
* required info from the pg_type row, just to make sure we don't
* make a cache entry for an invalid type OID.
*/
int16 typlen;
bool typbyval;
char typalign;
get_typlenbyvalalign(type_id, &typlen, &typbyval, &typalign);
typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
(void *) &type_id,
HASH_ENTER, &found);
if (typentry == NULL)
ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory")));
Assert(!found); /* it wasn't there a moment ago */
MemSet(typentry, 0, sizeof(TypeCacheEntry));
typentry->type_id = type_id;
typentry->typlen = typlen;
typentry->typbyval = typbyval;
typentry->typalign = typalign;
}
/* If we haven't already found the opclass, try to do so */
if (flags != 0 && typentry->btree_opc == InvalidOid)
{
typentry->btree_opc = lookup_default_opclass(type_id,
BTREE_AM_OID);
/* Only care about hash opclass if no btree opclass... */
if (typentry->btree_opc == InvalidOid)
{
if (typentry->hash_opc == InvalidOid)
typentry->hash_opc = lookup_default_opclass(type_id,
HASH_AM_OID);
}
else
{
/*
* If we find a btree opclass where previously we only found
* a hash opclass, forget the hash equality operator so we
* can use the btree operator instead.
*/
typentry->eq_opr = InvalidOid;
typentry->eq_opr_finfo.fn_oid = InvalidOid;
}
}
/* Look for requested operators and functions */
if ((flags & (TYPECACHE_EQ_OPR | TYPECACHE_EQ_OPR_FINFO)) &&
typentry->eq_opr == InvalidOid)
{
if (typentry->btree_opc != InvalidOid)
typentry->eq_opr = get_opclass_member(typentry->btree_opc,
BTEqualStrategyNumber);
if (typentry->eq_opr == InvalidOid &&
typentry->hash_opc != InvalidOid)
typentry->eq_opr = get_opclass_member(typentry->hash_opc,
HTEqualStrategyNumber);
}
if ((flags & TYPECACHE_LT_OPR) && typentry->lt_opr == InvalidOid)
{
if (typentry->btree_opc != InvalidOid)
typentry->lt_opr = get_opclass_member(typentry->btree_opc,
BTLessStrategyNumber);
}
if ((flags & TYPECACHE_GT_OPR) && typentry->gt_opr == InvalidOid)
{
if (typentry->btree_opc != InvalidOid)
typentry->gt_opr = get_opclass_member(typentry->btree_opc,
BTGreaterStrategyNumber);
}
if ((flags & (TYPECACHE_CMP_PROC | TYPECACHE_CMP_PROC_FINFO)) &&
typentry->cmp_proc == InvalidOid)
{
if (typentry->btree_opc != InvalidOid)
typentry->cmp_proc = get_opclass_proc(typentry->btree_opc,
BTORDER_PROC);
}
/*
* Set up fmgr lookup info as requested
*
* Note: we tell fmgr the finfo structures live in CacheMemoryContext,
* which is not quite right (they're really in DynaHashContext) but this
* will do for our purposes.
*/
if ((flags & TYPECACHE_EQ_OPR_FINFO) &&
typentry->eq_opr_finfo.fn_oid == InvalidOid &&
typentry->eq_opr != InvalidOid)
{
Oid eq_opr_func;
eq_opr_func = get_opcode(typentry->eq_opr);
if (eq_opr_func != InvalidOid)
fmgr_info_cxt(eq_opr_func, &typentry->eq_opr_finfo,
CacheMemoryContext);
}
if ((flags & TYPECACHE_CMP_PROC_FINFO) &&
typentry->cmp_proc_finfo.fn_oid == InvalidOid &&
typentry->cmp_proc != InvalidOid)
{
fmgr_info_cxt(typentry->cmp_proc, &typentry->cmp_proc_finfo,
CacheMemoryContext);
}
return typentry;
}
