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Speed up byteain by not parsing traditional-style input twice.

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Instead of laboriously computing the exact output length, use strlen
to get an upper bound cheaply.  (This is still O(N) of course, but
the constant factor is a lot less.)  This will typically result in
overallocating the output datum, but that's of little concern since
it's a short-lived allocation in just about all use-cases.

A simple microbenchmark showed about 40% speedup for long input
strings.

While here, make some cosmetic cleanups and add a test case that
covers the double-backslash code path in byteain and byteaout.

Author: Steven Niu <niushiji@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Stepan Neretin <slpmcf@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/ca315729-140b-426e-81a6-6cd5cfe7ecc5@gmail.com
This commit is contained in:
Tom Lane
2025-07-18 16:42:02 -04:00
parent 84409ed640
commit 3683af6170
3 changed files with 39 additions and 54 deletions
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79
src/backend/utils/adt/bytea.c
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@@ -182,27 +182,21 @@ bytea_overlay(bytea *t1, bytea *t2, int sp, int sl)
*
* Non-printable characters must be passed as '\nnn' (octal) and are
* converted to internal form. '\' must be passed as '\\'.
* ereport(ERROR, ...) if bad form.
*
* BUGS:
* The input is scanned twice.
* The error checking of input is minimal.
*/
Datum
byteain(PG_FUNCTION_ARGS)
{
char *inputText = PG_GETARG_CSTRING(0);
Node *escontext = fcinfo->context;
size_t len = strlen(inputText);
size_t bc;
char *tp;
char *rp;
int bc;
bytea *result;
/* Recognize hex input */
if (inputText[0] == '\\' && inputText[1] == 'x')
{
size_t len = strlen(inputText);
bc = (len - 2) / 2 + VARHDRSZ; /* maximum possible length */
result = palloc(bc);
bc = hex_decode_safe(inputText + 2, len - 2, VARDATA(result),
@@ -213,18 +207,33 @@ byteain(PG_FUNCTION_ARGS)
}
/* Else, it's the traditional escaped style */
for (bc = 0, tp = inputText; *tp != '\0'; bc++)
result = (bytea *) palloc(len + VARHDRSZ); /* maximum possible length */
tp = inputText;
rp = VARDATA(result);
while (*tp != '\0')
{
if (tp[0] != '\\')
tp++;
else if ((tp[0] == '\\') &&
(tp[1] >= '0' && tp[1] <= '3') &&
*rp++ = *tp++;
else if ((tp[1] >= '0' && tp[1] <= '3') &&
(tp[2] >= '0' && tp[2] <= '7') &&
(tp[3] >= '0' && tp[3] <= '7'))
{
int v;
v = VAL(tp[1]);
v <<= 3;
v += VAL(tp[2]);
v <<= 3;
*rp++ = v + VAL(tp[3]);
tp += 4;
else if ((tp[0] == '\\') &&
(tp[1] == '\\'))
}
else if (tp[1] == '\\')
{
*rp++ = '\\';
tp += 2;
}
else
{
/*
@@ -236,46 +245,8 @@ byteain(PG_FUNCTION_ARGS)
}
}
bc += VARHDRSZ;
result = (bytea *) palloc(bc);
SET_VARSIZE(result, bc);
tp = inputText;
rp = VARDATA(result);
while (*tp != '\0')
{
if (tp[0] != '\\')
*rp++ = *tp++;
else if ((tp[0] == '\\') &&
(tp[1] >= '0' && tp[1] <= '3') &&
(tp[2] >= '0' && tp[2] <= '7') &&
(tp[3] >= '0' && tp[3] <= '7'))
{
bc = VAL(tp[1]);
bc <<= 3;
bc += VAL(tp[2]);
bc <<= 3;
*rp++ = bc + VAL(tp[3]);
tp += 4;
}
else if ((tp[0] == '\\') &&
(tp[1] == '\\'))
{
*rp++ = '\\';
tp += 2;
}
else
{
/*
* We should never get here. The first pass should not allow it.
*/
ereturn(escontext, (Datum) 0,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type %s", "bytea")));
}
}
bc = rp - VARDATA(result); /* actual length */
SET_VARSIZE(result, bc + VARHDRSZ);
PG_RETURN_BYTEA_P(result);
}