Use standard librart sqrt function in pg_stat_statements

The stddev calculation included a faster but unportable sqrt function.
This is not worth the extra effort, and won't work everywhere. If the
standard library function is good enough for the SQL function it
should be good enough here too.

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index fee2aaacbe2a6cb7ca8285167ce94210083f97fe..da6c242631a4f4124f64c0cb02a20e236d16f86a 100644 (file)
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -57,6 +57,7 @@
  */
 #include "postgres.h"
 
+#include <math.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
@@ -326,7 +327,6 @@ static char *generate_normalized_query(pgssJumbleState *jstate, const char *quer
                                                  int *query_len_p, int encoding);
 static void fill_in_constant_lengths(pgssJumbleState *jstate, const char *query);
 static int     comp_location(const void *a, const void *b);
-static inline double sqrtd(const double x);
 
 
 /*
@@ -1583,7 +1583,7 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
                         */
                        if (tmp.calls > 1)
                                values[i++] =
-                                       Float8GetDatum(sqrtd(tmp.sum_var_time / tmp.calls));
+                                       Float8GetDatum(sqrt(tmp.sum_var_time / tmp.calls));
                        else
                                values[i++] = Float8GetDatum(0.0);
                }
@@ -2968,20 +2968,3 @@ comp_location(const void *a, const void *b)
        else
                return 0;
 }
-
-/*
- * fast sqrt algorithm: reference from Fast inverse square root algorithms.
- */
-static inline double
-sqrtd(const double x)
-{
-       double      x_half = 0.5 * x;
-       long long int   tmp = 0x5FE6EB50C7B537AAl - ( *(long long int*)&x >> 1);
-       double      x_result = * (double*)&tmp;
-
-       x_result *= (1.5 - (x_half * x_result * x_result));
-       /* If retry this calculation, it becomes higher precision at sqrt */
-       x_result *= (1.5 - (x_half * x_result * x_result));
-
-       return x_result * x;
-}