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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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19
src/backend/utils/adt/numeric.c
View File

@ -14,7 +14,7 @@
* Copyright (c) 1998-2007, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.98 2007/01/05 22:19:41 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.99 2007/01/16 21:41:13 neilc Exp $
*
*-------------------------------------------------------------------------
*/
@ -874,16 +874,17 @@ numeric_floor(PG_FUNCTION_ARGS)
}
/*
* width_bucket_numeric() -
* Implements the numeric version of the width_bucket() function
* defined by SQL2003. See also width_bucket_float8().
*
* '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 in for an equiwidth histogram
* 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).
* count+1). We don't allow "NaN" for any of the numeric arguments.
*/
Datum
width_bucket_numeric(PG_FUNCTION_ARGS)
@ -901,6 +902,13 @@ width_bucket_numeric(PG_FUNCTION_ARGS)
(errcode(ERRCODE_INVALID_ARGUMENT_FOR_WIDTH_BUCKET_FUNCTION),
errmsg("count must be greater than zero")));
if (NUMERIC_IS_NAN(operand) ||
NUMERIC_IS_NAN(bound1) ||
NUMERIC_IS_NAN(bound2))
ereport(ERROR,
(errcode(ERRCODE_INVALID_ARGUMENT_FOR_WIDTH_BUCKET_FUNCTION),
errmsg("operand, lower bound and upper bound cannot be NaN")));
init_var(&result_var);
init_var(&count_var);
@ -937,6 +945,7 @@ width_bucket_numeric(PG_FUNCTION_ARGS)
break;
}
/* if result exceeds the range of a legal int4, we ereport here */
result = numericvar_to_int4(&result_var);
free_var(&count_var);
@ -946,8 +955,6 @@ width_bucket_numeric(PG_FUNCTION_ARGS)
}
/*
* compute_bucket() -
*
* If 'operand' is not outside the bucket range, determine the correct
* bucket for it to go. The calculations performed by this function
* are derived directly from the SQL2003 spec.