nbtutils.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

	 * "break" statement below.
	 */
	for (i = 0;; cur++, i++)
	{
		if (i < numberOfKeys)
		{
			/* See comments above: any NULL implies cannot match qual */
			if (cur->sk_flags & SK_ISNULL)
			{
				so->qual_ok = false;

				/*
				 * Quit processing so we don't try to invoke comparison
				 * routines on NULLs.
				 */
				return;
			}
		}

		/*
		 * If we are at the end of the keys for a particular attr, finish up
		 * processing and emit the cleaned-up keys.
		 */
		if (i == numberOfKeys || cur->sk_attno != attno)
		{
			int			priorNumberOfEqualCols = numberOfEqualCols;

			/* check input keys are correctly ordered */
			if (i < numberOfKeys && cur->sk_attno < attno)
				elog(ERROR, "btree index keys must be ordered by attribute");

			/*
			 * If = has been specified, no other key will be used. In case of
			 * key > 2 && key == 1 and so on we have to set qual_ok to false
			 * before discarding the other keys.
			 */
			if (xform[BTEqualStrategyNumber - 1])
			{
				ScanKey		eq = xform[BTEqualStrategyNumber - 1];

				for (j = BTMaxStrategyNumber; --j >= 0;)
				{
					ScanKey		chk = xform[j];

					if (!chk || j == (BTEqualStrategyNumber - 1))
						continue;
					test = FunctionCall2(&chk->sk_func,
										 eq->sk_argument,
										 chk->sk_argument);
					if (!DatumGetBool(test))
					{
						so->qual_ok = false;
						break;
					}
				}
				xform[BTLessStrategyNumber - 1] = NULL;
				xform[BTLessEqualStrategyNumber - 1] = NULL;
				xform[BTGreaterEqualStrategyNumber - 1] = NULL;
				xform[BTGreaterStrategyNumber - 1] = NULL;
				/* track number of attrs for which we have "=" keys */
				numberOfEqualCols++;
			}
			else
			{
				/* track number of attrs for which we have "=" keys */
				if (hasOtherTypeEqual)
					numberOfEqualCols++;
			}

			/* keep only one of <, <= */
			if (xform[BTLessStrategyNumber - 1]
				&& xform[BTLessEqualStrategyNumber - 1])
			{
				ScanKey		lt = xform[BTLessStrategyNumber - 1];
				ScanKey		le = xform[BTLessEqualStrategyNumber - 1];

				test = FunctionCall2(&le->sk_func,
									 lt->sk_argument,
									 le->sk_argument);
				if (DatumGetBool(test))
					xform[BTLessEqualStrategyNumber - 1] = NULL;
				else
					xform[BTLessStrategyNumber - 1] = NULL;
			}

			/* keep only one of >, >= */
			if (xform[BTGreaterStrategyNumber - 1]
				&& xform[BTGreaterEqualStrategyNumber - 1])
			{
				ScanKey		gt = xform[BTGreaterStrategyNumber - 1];
				ScanKey		ge = xform[BTGreaterEqualStrategyNumber - 1];

				test = FunctionCall2(&ge->sk_func,
									 gt->sk_argument,
									 ge->sk_argument);
				if (DatumGetBool(test))
					xform[BTGreaterEqualStrategyNumber - 1] = NULL;
				else
					xform[BTGreaterStrategyNumber - 1] = NULL;
			}

			/*
			 * Emit the cleaned-up keys into the outkeys[] array.
			 */
			for (j = BTMaxStrategyNumber; --j >= 0;)
			{
				if (xform[j])
					memcpy(&outkeys[new_numberOfKeys++], xform[j],
						   sizeof(ScanKeyData));
			}

			/*
			 * If all attrs before this one had "=", include these keys into
			 * the required-keys count.
			 */
			if (priorNumberOfEqualCols == attno - 1)
				so->numberOfRequiredKeys = new_numberOfKeys;

			/*
			 * Exit loop here if done.
			 */
			if (i == numberOfKeys)
				break;

			/* Re-initialize for new attno */
			attno = cur->sk_attno;
			memset(xform, 0, sizeof(xform));
			hasOtherTypeEqual = false;
		}

		/* check strategy this key's operator corresponds to */
		j = cur->sk_strategy - 1;

		/* if wrong RHS data type, punt */
		if (cur->sk_subtype != InvalidOid)
		{
			memcpy(&outkeys[new_numberOfKeys++], cur,
				   sizeof(ScanKeyData));
			if (j == (BTEqualStrategyNumber - 1))
				hasOtherTypeEqual = true;
			continue;
		}

		/* have we seen one of these before? */
		if (xform[j])
		{
			/* yup, keep the more restrictive key */
			test = FunctionCall2(&cur->sk_func,
								 cur->sk_argument,
								 xform[j]->sk_argument);
			if (DatumGetBool(test))
				xform[j] = cur;
			else if (j == (BTEqualStrategyNumber - 1))
			{
				/* key == a && key == b, but a != b */
				so->qual_ok = false;
				return;
			}
		}
		else
		{
			/* nope, so remember this scankey */
			xform[j] = cur;
		}
	}

	so->numberOfKeys = new_numberOfKeys;

	/*
	 * If unique index and we have equality keys for all columns, set
	 * keys_are_unique flag for higher levels.
	 */
	if (relation->rd_index->indisunique &&
		relation->rd_rel->relnatts == numberOfEqualCols)
		scan->keys_are_unique = true;
}

/*
 * Test whether an indextuple satisfies all the scankey conditions.
 *
 * 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.
 */
bool
_bt_checkkeys(IndexScanDesc scan, IndexTuple tuple,
			  ScanDirection dir, bool *continuescan)
{
	BTScanOpaque so = (BTScanOpaque) scan->opaque;
	int			keysz = so->numberOfKeys;
	int			ikey;
	TupleDesc	tupdesc;
	ScanKey		key;

	*continuescan = true;

	/* If no keys, always scan the whole index */
	if (keysz == 0)
		return true;

	IncrIndexProcessed();

	tupdesc = RelationGetDescr(scan->indexRelation);

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

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

		/* btree doesn't support 'A is null' clauses, yet */
		if (key->sk_flags & SK_ISNULL)
		{
			/* we shouldn't get here, really; see _bt_preprocess_keys() */
			*continuescan = false;
			return false;
		}

		if (isNull)
		{
			/*
			 * 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 (ikey < so->numberOfRequiredKeys &&
				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, then we may be
			 * able to conclude no further tuples will pass, either. We have
			 * to look at the scan direction and the qual type.
			 *
			 * Note: the only case in which we would keep going after failing
			 * a required qual is if there are partially-redundant quals that
			 * _bt_preprocess_keys() was unable to eliminate.  For example,
			 * given "x > 4 AND x > 10" where both are cross-type comparisons
			 * and so not removable, we might start the scan at the x = 4
			 * boundary point.	The "x > 10" condition will fail until we pass
			 * x = 10, but we must not stop the scan on its account.
			 *
			 * 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 (ikey < so->numberOfRequiredKeys)
			{
				switch (key->sk_strategy)
				{
					case BTLessStrategyNumber:
					case BTLessEqualStrategyNumber:
						if (ScanDirectionIsForward(dir))
							*continuescan = false;
						break;
					case BTEqualStrategyNumber:
						*continuescan = false;
						break;
					case BTGreaterEqualStrategyNumber:
					case BTGreaterStrategyNumber:
						if (ScanDirectionIsBackward(dir))
							*continuescan = false;
						break;
					default:
						elog(ERROR, "unrecognized StrategyNumber: %d",
							 key->sk_strategy);
				}
			}

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

	/* If we get here, the tuple passes all quals. */
	return true;
}