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Make OVERLAPS operators conform to SQL92 spec regarding NULL handling.

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As I read it, the spec requires a non-null result in some cases where
one of the inputs is NULL: specifically, if the other endpoint of that
interval is between the endpoints of the other interval, then the result
is known TRUE despite the missing endpoint.  The spec could've been a
lot simpler if they did not intend this behavior.
I did not force an initdb for this change, but if you don't do one you'll
still see the old strict-function behavior.
This commit is contained in:
Tom Lane
2000-12-07 18:38:59 +00:00
parent 8bb4dab94d
commit 821f4673ff
3 changed files with 297 additions and 73 deletions
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114
src/backend/utils/adt/timestamp.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/timestamp.c,v 1.39 2000/12/03 20:45:36 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/timestamp.c,v 1.40 2000/12/07 18:38:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -825,53 +825,123 @@ interval_hash(PG_FUNCTION_ARGS)
return hash_any((char *) key, sizeof(double) + sizeof(int4));
}
/* overlaps_timestamp()
* Implements the SQL92 OVERLAPS operator.
* Algorithm from Date and Darwen, 1997
/* overlaps_timestamp() --- implements the SQL92 OVERLAPS operator.
*
* Algorithm is per SQL92 spec. This is much harder than you'd think
* because the spec requires us to deliver a non-null answer in some cases
* where some of the inputs are null.
*/
Datum
overlaps_timestamp(PG_FUNCTION_ARGS)
{
/* The arguments are Timestamps, but we leave them as generic Datums
* to avoid unnecessary conversions between value and reference forms...
* to avoid unnecessary conversions between value and reference forms
* --- not to mention possible dereferences of null pointers.
*/
Datum ts1 = PG_GETARG_DATUM(0);
Datum te1 = PG_GETARG_DATUM(1);
Datum ts2 = PG_GETARG_DATUM(2);
Datum te2 = PG_GETARG_DATUM(3);
bool ts1IsNull = PG_ARGISNULL(0);
bool te1IsNull = PG_ARGISNULL(1);
bool ts2IsNull = PG_ARGISNULL(2);
bool te2IsNull = PG_ARGISNULL(3);
#define TIMESTAMP_GT(t1,t2) \
DatumGetBool(DirectFunctionCall2(timestamp_gt,t1,t2))
#define TIMESTAMP_LT(t1,t2) \
DatumGetBool(DirectFunctionCall2(timestamp_lt,t1,t2))
#define TIMESTAMP_EQ(t1,t2) \
DatumGetBool(DirectFunctionCall2(timestamp_eq,t1,t2))
/* Make sure we have ordered pairs... */
if (TIMESTAMP_GT(ts1, te1))
/*
* If both endpoints of interval 1 are null, the result is null (unknown).
* If just one endpoint is null, take ts1 as the non-null one.
* Otherwise, take ts1 as the lesser endpoint.
*/
if (ts1IsNull)
{
Datum tt = ts1;
if (te1IsNull)
PG_RETURN_NULL();
/* swap null for non-null */
ts1 = te1;
te1 = tt;
te1IsNull = true;
}
if (TIMESTAMP_GT(ts2, te2))
else if (!te1IsNull)
{
Datum tt = ts2;
if (TIMESTAMP_GT(ts1, te1))
{
Datum tt = ts1;
ts2 = te2;
te2 = tt;
ts1 = te1;
te1 = tt;
}
}
PG_RETURN_BOOL((TIMESTAMP_GT(ts1, ts2) &&
(TIMESTAMP_LT(ts1, te2) || TIMESTAMP_LT(te1, te2))) ||
(TIMESTAMP_GT(ts2, ts1) &&
(TIMESTAMP_LT(ts2, te1) || TIMESTAMP_LT(te2, te1))) ||
TIMESTAMP_EQ(ts1, ts2));
/* Likewise for interval 2. */
if (ts2IsNull)
{
if (te2IsNull)
PG_RETURN_NULL();
/* swap null for non-null */
ts2 = te2;
te2IsNull = true;
}
else if (!te2IsNull)
{
if (TIMESTAMP_GT(ts2, te2))
{
Datum tt = ts2;
ts2 = te2;
te2 = tt;
}
}
/*
* At this point neither ts1 nor ts2 is null, so we can consider three
* cases: ts1 > ts2, ts1 < ts2, ts1 = ts2
*/
if (TIMESTAMP_GT(ts1, ts2))
{
/* This case is ts1 < te2 OR te1 < te2, which may look redundant
* but in the presence of nulls it's not quite completely so.
*/
if (te2IsNull)
PG_RETURN_NULL();
if (TIMESTAMP_LT(ts1, te2))
PG_RETURN_BOOL(true);
if (te1IsNull)
PG_RETURN_NULL();
/* If te1 is not null then we had ts1 <= te1 above, and we just
* found ts1 >= te2, hence te1 >= te2.
*/
PG_RETURN_BOOL(false);
}
else if (TIMESTAMP_LT(ts1, ts2))
{
/* This case is ts2 < te1 OR te2 < te1 */
if (te1IsNull)
PG_RETURN_NULL();
if (TIMESTAMP_LT(ts2, te1))
PG_RETURN_BOOL(true);
if (te2IsNull)
PG_RETURN_NULL();
/* If te2 is not null then we had ts2 <= te2 above, and we just
* found ts2 >= te1, hence te2 >= te1.
*/
PG_RETURN_BOOL(false);
}
else
{
/* For ts1 = ts2 the spec says te1 <> te2 OR te1 = te2, which is a
* rather silly way of saying "true if both are nonnull, else null".
*/
if (te1IsNull || te2IsNull)
PG_RETURN_NULL();
PG_RETURN_BOOL(true);
}
#undef TIMESTAMP_GT
#undef TIMESTAMP_LT
#undef TIMESTAMP_EQ
}