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Avoid detoast in texteq/textne/byteaeq/byteane for unequal-length strings.

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We can get the length of a compressed or out-of-line datum without actually
detoasting it.  If the lengths of two strings are unequal, we can then
conclude they are unequal without detoasting.  That saves considerable work
in an admittedly less-common case, without costing anything much when the
optimization doesn't apply.

Noah Misch
This commit is contained in:
Tom Lane 2011-01-18 14:09:22 -05:00
parent 6e1726d082
commit 1b393f4e5d
1 changed files with 75 additions and 41 deletions
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116
src/backend/utils/adt/varlena.c
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@ -1451,22 +1451,34 @@ text_cmp(text *arg1, text *arg2)
Datum
texteq(PG_FUNCTION_ARGS)
{
text *arg1 = PG_GETARG_TEXT_PP(0);
text *arg2 = PG_GETARG_TEXT_PP(1);
Datum arg1 = PG_GETARG_DATUM(0);
Datum arg2 = PG_GETARG_DATUM(1);
bool result;
Size len1,
len2;
/*
* Since we only care about equality or not-equality, we can avoid all the
* expense of strcoll() here, and just do bitwise comparison.
* expense of strcoll() here, and just do bitwise comparison. In fact,
* we don't even have to do a bitwise comparison if we can show the
* lengths of the strings are unequal; which might save us from having
* to detoast one or both values.
*/
if (VARSIZE_ANY_EXHDR(arg1) != VARSIZE_ANY_EXHDR(arg2))
len1 = toast_raw_datum_size(arg1);
len2 = toast_raw_datum_size(arg2);
if (len1 != len2)
result = false;
else
result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2),
VARSIZE_ANY_EXHDR(arg1)) == 0);
{
text *targ1 = DatumGetTextPP(arg1);
text *targ2 = DatumGetTextPP(arg2);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
result = (memcmp(VARDATA_ANY(targ1), VARDATA_ANY(targ2),
len1 - VARHDRSZ) == 0);
PG_FREE_IF_COPY(targ1, 0);
PG_FREE_IF_COPY(targ2, 1);
}
PG_RETURN_BOOL(result);
}
@ -1474,22 +1486,28 @@ texteq(PG_FUNCTION_ARGS)
Datum
textne(PG_FUNCTION_ARGS)
{
text *arg1 = PG_GETARG_TEXT_PP(0);
text *arg2 = PG_GETARG_TEXT_PP(1);
Datum arg1 = PG_GETARG_DATUM(0);
Datum arg2 = PG_GETARG_DATUM(1);
bool result;
Size len1,
len2;
/*
* Since we only care about equality or not-equality, we can avoid all the
* expense of strcoll() here, and just do bitwise comparison.
*/
if (VARSIZE_ANY_EXHDR(arg1) != VARSIZE_ANY_EXHDR(arg2))
/* See comment in texteq() */
len1 = toast_raw_datum_size(arg1);
len2 = toast_raw_datum_size(arg2);
if (len1 != len2)
result = true;
else
result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2),
VARSIZE_ANY_EXHDR(arg1)) != 0);
{
text *targ1 = DatumGetTextPP(arg1);
text *targ2 = DatumGetTextPP(arg2);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
result = (memcmp(VARDATA_ANY(targ1), VARDATA_ANY(targ2),
len1 - VARHDRSZ) != 0);
PG_FREE_IF_COPY(targ1, 0);
PG_FREE_IF_COPY(targ2, 1);
}
PG_RETURN_BOOL(result);
}
@ -2358,23 +2376,31 @@ SplitIdentifierString(char *rawstring, char separator,
Datum
byteaeq(PG_FUNCTION_ARGS)
{
bytea *arg1 = PG_GETARG_BYTEA_PP(0);
bytea *arg2 = PG_GETARG_BYTEA_PP(1);
int len1,
len2;
Datum arg1 = PG_GETARG_DATUM(0);
Datum arg2 = PG_GETARG_DATUM(1);
bool result;
Size len1,
len2;
len1 = VARSIZE_ANY_EXHDR(arg1);
len2 = VARSIZE_ANY_EXHDR(arg2);
/* fast path for different-length inputs */
/*
* We can use a fast path for unequal lengths, which might save us from
* having to detoast one or both values.
*/
len1 = toast_raw_datum_size(arg1);
len2 = toast_raw_datum_size(arg2);
if (len1 != len2)
result = false;
else
result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), len1) == 0);
{
bytea *barg1 = DatumGetByteaPP(arg1);
bytea *barg2 = DatumGetByteaPP(arg2);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
result = (memcmp(VARDATA_ANY(barg1), VARDATA_ANY(barg2),
len1 - VARHDRSZ) == 0);
PG_FREE_IF_COPY(barg1, 0);
PG_FREE_IF_COPY(barg2, 1);
}
PG_RETURN_BOOL(result);
}
@ -2382,23 +2408,31 @@ byteaeq(PG_FUNCTION_ARGS)
Datum
byteane(PG_FUNCTION_ARGS)
{
bytea *arg1 = PG_GETARG_BYTEA_PP(0);
bytea *arg2 = PG_GETARG_BYTEA_PP(1);
int len1,
len2;
Datum arg1 = PG_GETARG_DATUM(0);
Datum arg2 = PG_GETARG_DATUM(1);
bool result;
Size len1,
len2;
len1 = VARSIZE_ANY_EXHDR(arg1);
len2 = VARSIZE_ANY_EXHDR(arg2);
/* fast path for different-length inputs */
/*
* We can use a fast path for unequal lengths, which might save us from
* having to detoast one or both values.
*/
len1 = toast_raw_datum_size(arg1);
len2 = toast_raw_datum_size(arg2);
if (len1 != len2)
result = true;
else
result = (memcmp(VARDATA_ANY(arg1), VARDATA_ANY(arg2), len1) != 0);
{
bytea *barg1 = DatumGetByteaPP(arg1);
bytea *barg2 = DatumGetByteaPP(arg2);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
result = (memcmp(VARDATA_ANY(barg1), VARDATA_ANY(barg2),
len1 - VARHDRSZ) != 0);
PG_FREE_IF_COPY(barg1, 0);
PG_FREE_IF_COPY(barg2, 1);
}
PG_RETURN_BOOL(result);
}