diff options
Diffstat (limited to 'src/backend/utils/adt/numeric.c')
| -rw-r--r-- | src/backend/utils/adt/numeric.c | 78 |
1 files changed, 77 insertions, 1 deletions
diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c index f173f30211c..6a6f3d44afb 100644 --- a/src/backend/utils/adt/numeric.c +++ b/src/backend/utils/adt/numeric.c @@ -14,7 +14,7 @@ * Copyright (c) 1998-2007, PostgreSQL Global Development Group * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.101 2007/02/27 23:48:08 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.102 2007/05/08 18:56:47 neilc Exp $ * *------------------------------------------------------------------------- */ @@ -26,6 +26,7 @@ #include <limits.h> #include <math.h> +#include "access/hash.h" #include "catalog/pg_type.h" #include "libpq/pqformat.h" #include "utils/array.h" @@ -1149,6 +1150,81 @@ cmp_numerics(Numeric num1, Numeric num2) return result; } +Datum +hash_numeric(PG_FUNCTION_ARGS) +{ + Numeric key = PG_GETARG_NUMERIC(0); + Datum digit_hash; + Datum result; + int weight; + int start_offset; + int end_offset; + int i; + int hash_len; + + /* If it's NaN, don't try to hash the rest of the fields */ + if (NUMERIC_IS_NAN(key)) + PG_RETURN_UINT32(0); + + weight = key->n_weight; + start_offset = 0; + end_offset = 0; + + /* + * Omit any leading or trailing zeros from the input to the + * hash. The numeric implementation *should* guarantee that + * leading and trailing zeros are suppressed, but we're + * paranoid. Note that we measure the starting and ending offsets + * in units of NumericDigits, not bytes. + */ + for (i = 0; i < NUMERIC_NDIGITS(key); i++) + { + if (NUMERIC_DIGITS(key)[i] != (NumericDigit) 0) + break; + + start_offset++; + /* + * The weight is effectively the # of digits before the + * decimal point, so decrement it for each leading zero we + * skip. + */ + weight--; + } + + /* + * If there are no non-zero digits, then the value of the number + * is zero, regardless of any other fields. + */ + if (NUMERIC_NDIGITS(key) == start_offset) + PG_RETURN_UINT32(-1); + + for (i = NUMERIC_NDIGITS(key) - 1; i >= 0; i--) + { + if (NUMERIC_DIGITS(key)[i] != (NumericDigit) 0) + break; + + end_offset++; + } + + /* If we get here, there should be at least one non-zero digit */ + Assert(start_offset + end_offset < NUMERIC_NDIGITS(key)); + + /* + * Note that we don't hash on the Numeric's scale, since two + * numerics can compare equal but have different scales. We also + * don't hash on the sign, although we could: since a sign + * difference implies inequality, this shouldn't affect correctness. + */ + hash_len = NUMERIC_NDIGITS(key) - start_offset - end_offset; + digit_hash = hash_any((unsigned char *) (NUMERIC_DIGITS(key) + start_offset), + hash_len * sizeof(NumericDigit)); + + /* Mix in the weight, via XOR */ + result = digit_hash ^ weight; + + PG_RETURN_DATUM(result); +} + /* ---------------------------------------------------------------------- * |