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Implement width_bucket() for the float8 data type.

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The implementation is somewhat ugly logic-wise, but I don't see an
easy way to make it more concise.

When writing this, I noticed that my previous implementation of
width_bucket() doesn't handle NaN correctly:

    postgres=# select width_bucket('NaN', 1, 5, 5);
     width_bucket
    --------------
                6
    (1 row)

AFAICS SQL:2003 does not define a NaN value, so it doesn't address how
width_bucket() should behave here. The patch changes width_bucket() so
that ereport(ERROR) is raised if NaN is specified for the operand or the
lower or upper bounds to width_bucket(). For float8, NaN is disallowed
for any of the floating-point inputs, and +/- infinity is disallowed
for the histogram bounds (but allowed for the operand).

Update docs and regression tests, bump the catversion.
This commit is contained in:
Neil Conway
2007-01-16 21:41:14 +00:00
parent da07c81fe3
commit cf57ef4e50
8 changed files with 210 additions and 69 deletions
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84
src/backend/utils/adt/float.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/float.c,v 1.146 2007/01/06 20:21:29 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/float.c,v 1.147 2007/01/16 21:41:13 neilc Exp $
*
*-------------------------------------------------------------------------
*/
@ -2745,6 +2745,88 @@ float84ge(PG_FUNCTION_ARGS)
PG_RETURN_BOOL(float8_cmp_internal(arg1, arg2) >= 0);
}
/*
* Implements the float8 version of the width_bucket() function
* defined by SQL2003. See also width_bucket_numeric().
*
* 'bound1' and 'bound2' are the lower and upper bounds of the
* histogram's range, respectively. 'count' is the number of buckets
* in the histogram. width_bucket() returns an integer indicating the
* bucket number that 'operand' belongs to in an equiwidth histogram
* with the specified characteristics. An operand smaller than the
* lower bound is assigned to bucket 0. An operand greater than the
* upper bound is assigned to an additional bucket (with number
* count+1). We don't allow "NaN" for any of the float8 inputs, and we
* don't allow either of the histogram bounds to be +/- infinity.
*/
Datum
width_bucket_float8(PG_FUNCTION_ARGS)
{
float8 operand = PG_GETARG_FLOAT8(0);
float8 bound1 = PG_GETARG_FLOAT8(1);
float8 bound2 = PG_GETARG_FLOAT8(2);
int32 count = PG_GETARG_INT32(3);
int32 result;
if (count <= 0.0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_ARGUMENT_FOR_WIDTH_BUCKET_FUNCTION),
errmsg("count must be greater than zero")));
if (isnan(operand) || isnan(bound1) || isnan(bound2))
ereport(ERROR,
(errcode(ERRCODE_INVALID_ARGUMENT_FOR_WIDTH_BUCKET_FUNCTION),
errmsg("operand, lower bound and upper bound cannot be NaN")));
/* Note that we allow "operand" to be infinite */
if (is_infinite(bound1) || is_infinite(bound2))
ereport(ERROR,
(errcode(ERRCODE_INVALID_ARGUMENT_FOR_WIDTH_BUCKET_FUNCTION),
errmsg("lower and upper bounds must be finite")));
if (bound1 < bound2)
{
if (operand < bound1)
result = 0;
else if (operand >= bound2)
{
result = count + 1;
/* check for overflow */
if (result < count)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("integer out of range")));
}
else
result = ((float8) count * (operand - bound1) / (bound2 - bound1)) + 1;
}
else if (bound1 > bound2)
{
if (operand > bound1)
result = 0;
else if (operand <= bound2)
{
result = count + 1;
/* check for overflow */
if (result < count)
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("integer out of range")));
}
else
result = ((float8) count * (bound1 - operand) / (bound1 - bound2)) + 1;
}
else
{
ereport(ERROR,
(errcode(ERRCODE_INVALID_ARGUMENT_FOR_WIDTH_BUCKET_FUNCTION),
errmsg("lower bound cannot equal upper bound")));
result = 0; /* keep the compiler quiet */
}
PG_RETURN_INT32(result);
}
/* ========== PRIVATE ROUTINES ========== */
#ifndef HAVE_CBRT