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Hand code string to integer conversion for performance.

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As benchmarks show, using libc's string-to-integer conversion is
pretty slow. At least part of the reason for that is that strtol[l]
have to be more generic than what largely is required inside pg.

This patch considerably speeds up int2/int4 input (int8 already was
already using hand-rolled code).

Most of the existing pg_atoi callers have been converted. But as one
requires pg_atoi's custom delimiter functionality, and as it seems
likely that there's external pg_atoi users, it seems sensible to just
keep pg_atoi around.

Author: Andres Freund
Reviewed-By: Robert Haas
Discussion: https://postgr.es/m/20171208214437.qgn6zdltyq5hmjpk@alap3.anarazel.de
This commit is contained in:
Andres Freund
2018-07-22 14:58:01 -07:00
parent 3522d0eaba
commit 86eaf208ea
13 changed files with 176 additions and 25 deletions
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149
src/backend/utils/adt/numutils.c
View File

@@ -18,6 +18,7 @@
#include <limits.h>
#include <ctype.h>
#include "common/int.h"
#include "utils/builtins.h"
/*
@@ -108,6 +109,154 @@ pg_atoi(const char *s, int size, int c)
return (int32) l;
}
/*
* Convert input string to a signed 16 bit integer.
*
* Allows any number of leading or trailing whitespace characters. Will throw
* ereport() upon bad input format or overflow.
*
* NB: Accumulate input as a negative number, to deal with two's complement
* representation of the most negative number, which can't be represented as a
* positive number.
*/
int16
pg_strtoint16(const char *s)
{
const char *ptr = s;
int16 tmp = 0;
bool neg = false;
/* skip leading spaces */
while (likely(*ptr) && isspace((unsigned char) *ptr))
ptr++;
/* handle sign */
if (*ptr == '-')
{
ptr++;
neg = true;
}
else if (*ptr == '+')
ptr++;
/* require at least one digit */
if (unlikely(!isdigit((unsigned char) *ptr)))
goto invalid_syntax;
/* process digits */
while (*ptr && isdigit((unsigned char) *ptr))
{
int8 digit = (*ptr++ - '0');
if (unlikely(pg_mul_s16_overflow(tmp, 10, &tmp)) ||
unlikely(pg_sub_s16_overflow(tmp, digit, &tmp)))
goto out_of_range;
}
/* allow trailing whitespace, but not other trailing chars */
while (*ptr != '\0' && isspace((unsigned char) *ptr))
ptr++;
if (unlikely(*ptr != '\0'))
goto invalid_syntax;
if (!neg)
{
/* could fail if input is most negative number */
if (unlikely(tmp == PG_INT16_MIN))
goto out_of_range;
tmp = -tmp;
}
return tmp;
out_of_range:
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("value \"%s\" is out of range for type %s",
s, "smallint")));
invalid_syntax:
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type %s: \"%s\"",
"smallint", s)));
}
/*
* Convert input string to a signed 32 bit integer.
*
* Allows any number of leading or trailing whitespace characters. Will throw
* ereport() upon bad input format or overflow.
*
* NB: Accumulate input as a negative number, to deal with two's complement
* representation of the most negative number, which can't be represented as a
* positive number.
*/
int32
pg_strtoint32(const char *s)
{
const char *ptr = s;
int32 tmp = 0;
bool neg = false;
/* skip leading spaces */
while (likely(*ptr) && isspace((unsigned char) *ptr))
ptr++;
/* handle sign */
if (*ptr == '-')
{
ptr++;
neg = true;
}
else if (*ptr == '+')
ptr++;
/* require at least one digit */
if (unlikely(!isdigit((unsigned char) *ptr)))
goto invalid_syntax;
/* process digits */
while (*ptr && isdigit((unsigned char) *ptr))
{
int8 digit = (*ptr++ - '0');
if (unlikely(pg_mul_s32_overflow(tmp, 10, &tmp)) ||
unlikely(pg_sub_s32_overflow(tmp, digit, &tmp)))
goto out_of_range;
}
/* allow trailing whitespace, but not other trailing chars */
while (*ptr != '\0' && isspace((unsigned char) *ptr))
ptr++;
if (unlikely(*ptr != '\0'))
goto invalid_syntax;
if (!neg)
{
/* could fail if input is most negative number */
if (unlikely(tmp == PG_INT32_MIN))
goto out_of_range;
tmp = -tmp;
}
return tmp;
out_of_range:
ereport(ERROR,
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
errmsg("value \"%s\" is out of range for type %s",
s, "integer")));
invalid_syntax:
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type %s: \"%s\"",
"integer", s)));
}
/*
* pg_itoa: converts a signed 16-bit integer to its string representation
*