diff options
Diffstat (limited to 'src/backend/utils/adt/float.c')
| -rw-r--r-- | src/backend/utils/adt/float.c | 78 |
1 files changed, 68 insertions, 10 deletions
diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c index 0a906854f58..29a2124e5f3 100644 --- a/src/backend/utils/adt/float.c +++ b/src/backend/utils/adt/float.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/utils/adt/float.c,v 1.121 2006/03/05 15:58:41 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/utils/adt/float.c,v 1.122 2006/03/10 20:15:25 neilc Exp $ * *------------------------------------------------------------------------- */ @@ -1861,11 +1861,13 @@ setseed(PG_FUNCTION_ARGS) * FLOAT AGGREGATE OPERATORS * ========================= * - * float8_accum - accumulate for AVG(), STDDEV(), etc - * float4_accum - same, but input data is float4 - * float8_avg - produce final result for float AVG() - * float8_variance - produce final result for float VARIANCE() - * float8_stddev - produce final result for float STDDEV() + * float8_accum - accumulate for AVG(), variance aggregates, etc. + * float4_accum - same, but input data is float4 + * float8_avg - produce final result for float AVG() + * float8_var_samp - produce final result for float VAR_SAMP() + * float8_var_pop - produce final result for float VAR_POP() + * float8_stddev_samp - produce final result for float STDDEV_SAMP() + * float8_stddev_pop - produce final result for float STDDEV_POP() * * The transition datatype for all these aggregates is a 3-element array * of float8, holding the values N, sum(X), sum(X*X) in that order. @@ -2015,7 +2017,7 @@ float8_avg(PG_FUNCTION_ARGS) } Datum -float8_variance(PG_FUNCTION_ARGS) +float8_var_pop(PG_FUNCTION_ARGS) { ArrayType *transarray = PG_GETARG_ARRAYTYPE_P(0); float8 *transvalues; @@ -2024,7 +2026,35 @@ float8_variance(PG_FUNCTION_ARGS) sumX2, numerator; - transvalues = check_float8_array(transarray, "float8_variance"); + transvalues = check_float8_array(transarray, "float8_var_pop"); + N = transvalues[0]; + sumX = transvalues[1]; + sumX2 = transvalues[2]; + + /* Population variance is undefined when N is 0, so return NULL */ + if (N == 0.0) + PG_RETURN_NULL(); + + numerator = N * sumX2 - sumX * sumX; + + /* Watch out for roundoff error producing a negative numerator */ + if (numerator <= 0.0) + PG_RETURN_FLOAT8(0.0); + + PG_RETURN_FLOAT8(numerator / (N * N)); +} + +Datum +float8_var_samp(PG_FUNCTION_ARGS) +{ + ArrayType *transarray = PG_GETARG_ARRAYTYPE_P(0); + float8 *transvalues; + float8 N, + sumX, + sumX2, + numerator; + + transvalues = check_float8_array(transarray, "float8_var_samp"); N = transvalues[0]; sumX = transvalues[1]; sumX2 = transvalues[2]; @@ -2043,7 +2073,35 @@ float8_variance(PG_FUNCTION_ARGS) } Datum -float8_stddev(PG_FUNCTION_ARGS) +float8_stddev_pop(PG_FUNCTION_ARGS) +{ + ArrayType *transarray = PG_GETARG_ARRAYTYPE_P(0); + float8 *transvalues; + float8 N, + sumX, + sumX2, + numerator; + + transvalues = check_float8_array(transarray, "float8_stddev_pop"); + N = transvalues[0]; + sumX = transvalues[1]; + sumX2 = transvalues[2]; + + /* Population stddev is undefined when N is 0, so return NULL */ + if (N == 0.0) + PG_RETURN_NULL(); + + numerator = N * sumX2 - sumX * sumX; + + /* Watch out for roundoff error producing a negative numerator */ + if (numerator <= 0.0) + PG_RETURN_FLOAT8(0.0); + + PG_RETURN_FLOAT8(sqrt(numerator / (N * N))); +} + +Datum +float8_stddev_samp(PG_FUNCTION_ARGS) { ArrayType *transarray = PG_GETARG_ARRAYTYPE_P(0); float8 *transvalues; @@ -2052,7 +2110,7 @@ float8_stddev(PG_FUNCTION_ARGS) sumX2, numerator; - transvalues = check_float8_array(transarray, "float8_stddev"); + transvalues = check_float8_array(transarray, "float8_stddev_samp"); N = transvalues[0]; sumX = transvalues[1]; sumX2 = transvalues[2]; |