nbtutils.c

postgresql8.3.4源码,开源数据库

			 */
			Assert(j != (BTEqualStrategyNumber - 1));
			continue;
		}

		/* have we seen one of these before? */
		if (xform[j] == NULL)
		{
			/* nope, so remember this scankey */
			xform[j] = cur;
		}
		else
		{
			/* yup, keep only the more restrictive key */

			/* if either arg is NULL, don't try to compare */
			if ((cur->sk_flags | xform[j]->sk_flags) & SK_ISNULL)
			{
				/* at least one of them must be an IS NULL clause */
				Assert(j == (BTEqualStrategyNumber - 1));
				Assert((cur->sk_flags | xform[j]->sk_flags) & SK_SEARCHNULL);
				/* if one is and one isn't, the search must fail */
				if ((cur->sk_flags ^ xform[j]->sk_flags) & SK_SEARCHNULL)
				{
					so->qual_ok = false;
					return;
				}
				/* we have duplicate IS NULL clauses, ignore the newer one */
				continue;
			}

			if (_bt_compare_scankey_args(scan, cur, cur, xform[j],
										 &test_result))
			{
				if (test_result)
					xform[j] = cur;
				else if (j == (BTEqualStrategyNumber - 1))
				{
					/* key == a && key == b, but a != b */
					so->qual_ok = false;
					return;
				}
				/* else old key is more restrictive, keep it */
			}
			else
			{
				/*
				 * We can't determine which key is more restrictive.  Keep the
				 * previous one in xform[j] and push this one directly to the
				 * output array.
				 */
				ScanKey		outkey = &outkeys[new_numberOfKeys++];

				memcpy(outkey, cur, sizeof(ScanKeyData));
				if (numberOfEqualCols == attno - 1)
					_bt_mark_scankey_required(outkey);
			}
		}
	}

	so->numberOfKeys = new_numberOfKeys;
}

/*
 * Compare two scankey values using a specified operator.  Both values
 * must be already known non-NULL.
 *
 * The test we want to perform is logically "leftarg op rightarg", where
 * leftarg and rightarg are the sk_argument values in those ScanKeys, and
 * the comparison operator is the one in the op ScanKey.  However, in
 * cross-data-type situations we may need to look up the correct operator in
 * the index's opfamily: it is the one having amopstrategy = op->sk_strategy
 * and amoplefttype/amoprighttype equal to the two argument datatypes.
 *
 * If the opfamily doesn't supply a complete set of cross-type operators we
 * may not be able to make the comparison.	If we can make the comparison
 * we store the operator result in *result and return TRUE.  We return FALSE
 * if the comparison could not be made.
 *
 * Note: op always points at the same ScanKey as either leftarg or rightarg.
 * Since we don't scribble on the scankeys, this aliasing should cause no
 * trouble.
 *
 * Note: this routine needs to be insensitive to any DESC option applied
 * to the index column.  For example, "x < 4" is a tighter constraint than
 * "x < 5" regardless of which way the index is sorted.  We don't worry about
 * NULLS FIRST/LAST either, since the given values are never nulls.
 */
static bool
_bt_compare_scankey_args(IndexScanDesc scan, ScanKey op,
						 ScanKey leftarg, ScanKey rightarg,
						 bool *result)
{
	Relation	rel = scan->indexRelation;
	Oid			lefttype,
				righttype,
				optype,
				opcintype,
				cmp_op;
	StrategyNumber strat;

	/*
	 * The opfamily we need to worry about is identified by the index column.
	 */
	Assert(leftarg->sk_attno == rightarg->sk_attno);

	opcintype = rel->rd_opcintype[leftarg->sk_attno - 1];

	/*
	 * Determine the actual datatypes of the ScanKey arguments.  We have to
	 * support the convention that sk_subtype == InvalidOid means the opclass
	 * input type; this is a hack to simplify life for ScanKeyInit().
	 */
	lefttype = leftarg->sk_subtype;
	if (lefttype == InvalidOid)
		lefttype = opcintype;
	righttype = rightarg->sk_subtype;
	if (righttype == InvalidOid)
		righttype = opcintype;
	optype = op->sk_subtype;
	if (optype == InvalidOid)
		optype = opcintype;

	/*
	 * If leftarg and rightarg match the types expected for the "op" scankey,
	 * we can use its already-looked-up comparison function.
	 */
	if (lefttype == opcintype && righttype == optype)
	{
		*result = DatumGetBool(FunctionCall2(&op->sk_func,
											 leftarg->sk_argument,
											 rightarg->sk_argument));
		return true;
	}

	/*
	 * Otherwise, we need to go to the syscache to find the appropriate
	 * operator.  (This cannot result in infinite recursion, since no
	 * indexscan initiated by syscache lookup will use cross-data-type
	 * operators.)
	 *
	 * If the sk_strategy was flipped by _bt_mark_scankey_with_indoption, we
	 * have to un-flip it to get the correct opfamily member.
	 */
	strat = op->sk_strategy;
	if (op->sk_flags & SK_BT_DESC)
		strat = BTCommuteStrategyNumber(strat);

	cmp_op = get_opfamily_member(rel->rd_opfamily[leftarg->sk_attno - 1],
								 lefttype,
								 righttype,
								 strat);
	if (OidIsValid(cmp_op))
	{
		RegProcedure cmp_proc = get_opcode(cmp_op);

		if (RegProcedureIsValid(cmp_proc))
		{
			*result = DatumGetBool(OidFunctionCall2(cmp_proc,
													leftarg->sk_argument,
													rightarg->sk_argument));
			return true;
		}
	}

	/* Can't make the comparison */
	*result = false;			/* suppress compiler warnings */
	return false;
}

/*
 * Mark a scankey with info from the index's indoption array.
 *
 * We copy the appropriate indoption value into the scankey sk_flags
 * (shifting to avoid clobbering system-defined flag bits).  Also, if
 * the DESC option is set, commute (flip) the operator strategy number.
 *
 * This function is applied to the *input* scankey structure; therefore
 * on a rescan we will be looking at already-processed scankeys.  Hence
 * we have to be careful not to re-commute the strategy if we already did it.
 * It's a bit ugly to modify the caller's copy of the scankey but in practice
 * there shouldn't be any problem, since the index's indoptions are certainly
 * not going to change while the scankey survives.
 */
static void
_bt_mark_scankey_with_indoption(ScanKey skey, int16 *indoption)
{
	int			addflags;

	addflags = indoption[skey->sk_attno - 1] << SK_BT_INDOPTION_SHIFT;
	if ((addflags & SK_BT_DESC) && !(skey->sk_flags & SK_BT_DESC))
		skey->sk_strategy = BTCommuteStrategyNumber(skey->sk_strategy);
	skey->sk_flags |= addflags;

	if (skey->sk_flags & SK_ROW_HEADER)
	{
		ScanKey		subkey = (ScanKey) DatumGetPointer(skey->sk_argument);

		for (;;)
		{
			Assert(subkey->sk_flags & SK_ROW_MEMBER);
			addflags = indoption[subkey->sk_attno - 1] << SK_BT_INDOPTION_SHIFT;
			if ((addflags & SK_BT_DESC) && !(subkey->sk_flags & SK_BT_DESC))
				subkey->sk_strategy = BTCommuteStrategyNumber(subkey->sk_strategy);
			subkey->sk_flags |= addflags;
			if (subkey->sk_flags & SK_ROW_END)
				break;
			subkey++;
		}
	}
}

/*
 * Mark a scankey as "required to continue the scan".
 *
 * Depending on the operator type, the key may be required for both scan
 * directions or just one.	Also, if the key is a row comparison header,
 * we have to mark the appropriate subsidiary ScanKeys as required.  In
 * such cases, the first subsidiary key is required, but subsequent ones
 * are required only as long as they correspond to successive index columns
 * and match the leading column as to sort direction.
 * Otherwise the row comparison ordering is different from the index ordering
 * and so we can't stop the scan on the basis of those lower-order columns.
 *
 * Note: when we set required-key flag bits in a subsidiary scankey, we are
 * scribbling on a data structure belonging to the index AM's caller, not on
 * our private copy.  This should be OK because the marking will not change
 * from scan to scan within a query, and so we'd just re-mark the same way
 * anyway on a rescan.	Something to keep an eye on though.
 */
static void
_bt_mark_scankey_required(ScanKey skey)
{
	int			addflags;

	switch (skey->sk_strategy)
	{
		case BTLessStrategyNumber:
		case BTLessEqualStrategyNumber:
			addflags = SK_BT_REQFWD;
			break;
		case BTEqualStrategyNumber:
			addflags = SK_BT_REQFWD | SK_BT_REQBKWD;
			break;
		case BTGreaterEqualStrategyNumber:
		case BTGreaterStrategyNumber:
			addflags = SK_BT_REQBKWD;
			break;
		default:
			elog(ERROR, "unrecognized StrategyNumber: %d",
				 (int) skey->sk_strategy);
			addflags = 0;		/* keep compiler quiet */
			break;
	}

	skey->sk_flags |= addflags;

	if (skey->sk_flags & SK_ROW_HEADER)
	{
		ScanKey		subkey = (ScanKey) DatumGetPointer(skey->sk_argument);
		AttrNumber	attno = skey->sk_attno;

		/* First subkey should be same as the header says */
		Assert(subkey->sk_attno == attno);

		for (;;)
		{
			Assert(subkey->sk_flags & SK_ROW_MEMBER);
			if (subkey->sk_attno != attno)
				break;			/* non-adjacent key, so not required */
			if (subkey->sk_strategy != skey->sk_strategy)
				break;			/* wrong direction, so not required */
			subkey->sk_flags |= addflags;
			if (subkey->sk_flags & SK_ROW_END)
				break;
			subkey++;
			attno++;
		}
	}
}

/*
 * Test whether an indextuple satisfies all the scankey conditions.
 *
 * If so, copy its TID into scan->xs_ctup.t_self, and return TRUE.
 * If not, return FALSE (xs_ctup is not changed).
 *
 * If the tuple fails to pass the qual, we also determine whether there's
 * any need to continue the scan beyond this tuple, and set *continuescan
 * accordingly.  See comments for _bt_preprocess_keys(), above, about how
 * this is done.
 *
 * 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
 * continuescan: output parameter (will be set correctly in all cases)
 */
bool
_bt_checkkeys(IndexScanDesc scan,
			  Page page, OffsetNumber offnum,
			  ScanDirection dir, bool *continuescan)
{
	ItemId		iid = PageGetItemId(page, offnum);
	bool		tuple_valid;
	IndexTuple	tuple;
	TupleDesc	tupdesc;
	BTScanOpaque so;
	int			keysz;
	int			ikey;
	ScanKey		key;

	*continuescan = true;		/* default assumption */

	/*
	 * If the scan specifies not to return killed tuples, then we treat a
	 * killed tuple as not passing the qual.  Most of the time, it's a win to
	 * not bother examining the tuple's index keys, but just return
	 * immediately with continuescan = true to proceed to the next tuple.
	 * However, if this is the last tuple on the page, we should check the
	 * index keys to prevent uselessly advancing to the next page.
	 */
	if (scan->ignore_killed_tuples && ItemIdIsDead(iid))
	{
		/* return immediately if there are more tuples on the page */
		if (ScanDirectionIsForward(dir))
		{
			if (offnum < PageGetMaxOffsetNumber(page))
				return false;
		}
		else
		{
			BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);

			if (offnum > P_FIRSTDATAKEY(opaque))
				return false;
		}

		/*
		 * OK, we want to check the keys, but we'll return FALSE even if the
		 * tuple passes the key tests.
		 */
		tuple_valid = false;
	}
	else
		tuple_valid = true;

	tuple = (IndexTuple) PageGetItem(page, iid);

	IncrIndexProcessed();

	tupdesc = RelationGetDescr(scan->indexRelation);
	so = (BTScanOpaque) scan->opaque;
	keysz = so->numberOfKeys;

	for (key = so->keyData, ikey = 0; ikey < keysz; key++, ikey++)
	{
		Datum		datum;
		bool		isNull;
		Datum		test;

		/* row-comparison keys need special processing */
		if (key->sk_flags & SK_ROW_HEADER)
		{
			if (_bt_check_rowcompare(key, tuple, tupdesc, dir, continuescan))
				continue;
			return false;
		}

		datum = index_getattr(tuple,
							  key->sk_attno,
							  tupdesc,
							  &isNull);

		if (key->sk_flags & SK_ISNULL)
		{
			/* Handle IS NULL tests */
			Assert(key->sk_flags & SK_SEARCHNULL);

			if (isNull)
				continue;		/* tuple satisfies this qual */

			/*
			 * Tuple fails this qual.  If it's a required qual for the current
			 * scan direction, then we can conclude no further tuples will
			 * pass, either.
			 */
			if ((key->sk_flags & SK_BT_REQFWD) &&
				ScanDirectionIsForward(dir))
				*continuescan = false;
			else if ((key->sk_flags & SK_BT_REQBKWD) &&
					 ScanDirectionIsBackward(dir))
				*continuescan = false;

			/*
			 * In any case, this indextuple doesn't match the qual.
			 */
			return false;
		}

		if (isNull)
		{
			if (key->sk_flags & SK_BT_NULLS_FIRST)
			{
				/*
				 * Since NULLs are sorted before non-NULLs, we know we have
				 * reached the lower limit of the range of values for this
				 * index attr.	On a backward scan, we can stop if this qual
				 * is one of the "must match" subset.  On a forward scan,
				 * however, we should keep going.
				 */
				if ((key->sk_flags & SK_BT_REQBKWD) &&
					ScanDirectionIsBackward(dir))
					*continuescan = false;
			}
			else
			{
				/*
				 * Since NULLs are sorted after non-NULLs, we know we have
				 * reached the upper limit of the range of values for this
				 * index attr.	On a forward scan, we can stop if this qual is
				 * one of the "must match" subset.	On a backward scan,
				 * however, we should keep going.
				 */
				if ((key->sk_flags & SK_BT_REQFWD) &&
					ScanDirectionIsForward(dir))
					*continuescan = false;
			}

			/*
			 * In any case, this indextuple doesn't match the qual.
			 */
			return false;
		}

		test = FunctionCall2(&key->sk_func, datum, key->sk_argument);

		if (!DatumGetBool(test))
		{
			/*
			 * Tuple fails this qual.  If it's a required qual for the current
			 * scan direction, then we can conclude no further tuples will
			 * pass, either.
			 *
			 * Note: because we stop the scan as soon as any required equality
			 * qual fails, it is critical that equality quals be used for the
			 * initial positioning in _bt_first() when they are available. See
			 * comments in _bt_first().
			 */
			if ((key->sk_flags & SK_BT_REQFWD) &&
				ScanDirectionIsForward(dir))
				*continuescan = false;
			else if ((key->sk_flags & SK_BT_REQBKWD) &&
					 ScanDirectionIsBackward(dir))
				*continuescan = false;

			/*
			 * In any case, this indextuple doesn't match the qual.
			 */
			return false;
		}
	}

	/* If we get here, the tuple passes all index quals. */
	if (tuple_valid)
		scan->xs_ctup.t_self = tuple->t_tid;

	return tuple_valid;
}