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Change the parser to convert SQL "position" and "substring" syntax to

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position() and substring() functions, so that it works transparently for
bit types as well.  Alias the text functions appropriately.

Add position() for bit types.

Add new constant node T_BitString that represents literals of the form
B'1001 and pass those to zpbit type.
This commit is contained in:
Peter Eisentraut
2000-10-31 10:22:13 +00:00
parent d397c1c8a2
commit 73874a06f0
14 changed files with 214 additions and 47 deletions
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102
src/backend/utils/adt/varbit.c
View File

@ -9,7 +9,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/varbit.c,v 1.9 2000/08/26 21:53:41 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/varbit.c,v 1.10 2000/10/31 10:22:11 petere Exp $
*
*-------------------------------------------------------------------------
*/
@ -1053,8 +1053,8 @@ bitshiftright(PG_FUNCTION_ARGS)
/* Negative shift is a shift to the left */
if (shft < 0)
PG_RETURN_DATUM(DirectFunctionCall2(bitshiftleft,
VarBitPGetDatum(arg),
Int32GetDatum(-shft)));
VarBitPGetDatum(arg),
Int32GetDatum(-shft)));
result = (VarBit *) palloc(VARSIZE(arg));
VARATT_SIZEP(result) = VARSIZE(arg);
@ -1146,3 +1146,99 @@ bittoint4(PG_FUNCTION_ARGS)
PG_RETURN_INT32(result);
}
/* Determines the position of S2 in the bitstring S1 (1-based string).
* If S2 does not appear in S1 this function returns 0.
* If S2 is of length 0 this function returns 1.
*/
Datum
bitposition(PG_FUNCTION_ARGS)
{
VarBit *substr = PG_GETARG_VARBIT_P(1);
VarBit *arg = PG_GETARG_VARBIT_P(0);
int substr_length,
arg_length,
i,
is;
bits8 *s, /* pointer into substring */
*p; /* pointer into arg */
bits8 cmp, /* shifted substring byte to compare */
mask1, /* mask for substring byte shifted right */
mask2, /* mask for substring byte shifted left */
end_mask, /* pad mask for last substring byte */
arg_mask; /* pad mask for last argument byte */
bool is_match;
/* Get the substring length */
substr_length = VARBITLEN(substr);
arg_length = VARBITLEN(arg);
/* Argument has 0 length or substring longer than argument, return 0 */
if (arg_length == 0 || substr_length > arg_length)
PG_RETURN_INT32(0);
/* 0-length means return 1 */
if (substr_length == 0)
PG_RETURN_INT32(1);
/* Initialise the padding masks */
end_mask = BITMASK << VARBITPAD(substr);
arg_mask = BITMASK << VARBITPAD(arg);
for (i = 0; i < VARBITBYTES(arg) - VARBITBYTES(substr) + 1; i++)
{
for (is = 0; is < BITS_PER_BYTE; is++) {
is_match = true;
p = VARBITS(arg) + i;
mask1 = BITMASK >> is;
mask2 = ~mask1;
for (s = VARBITS(substr);
is_match && s < VARBITEND(substr); s++)
{
cmp = *s >> is;
if (s == VARBITEND(substr) - 1)
{
mask1 &= end_mask >> is;
if (p == VARBITEND(arg) - 1) {
/* Check that there is enough of arg left */
if (mask1 & ~arg_mask) {
is_match = false;
break;
}
mask1 &= arg_mask;
}
}
is_match = ((cmp ^ *p) & mask1) == 0;
if (!is_match)
break;
// Move on to the next byte
p++;
if (p == VARBITEND(arg)) {
mask2 = end_mask << (BITS_PER_BYTE - is);
is_match = mask2 == 0;
elog(NOTICE,"S. %d %d em=%2x sm=%2x r=%d",
i,is,end_mask,mask2,is_match);
break;
}
cmp = *s << (BITS_PER_BYTE - is);
if (s == VARBITEND(substr) - 1)
{
mask2 &= end_mask << (BITS_PER_BYTE - is);
if (p == VARBITEND(arg) - 1) {
if (mask2 & ~arg_mask) {
is_match = false;
break;
}
mask2 &= arg_mask;
}
}
is_match = ((cmp ^ *p) & mask2) == 0;
}
/* Have we found a match */
if (is_match)
PG_RETURN_INT32(i*BITS_PER_BYTE + is + 1);
}
}
PG_RETURN_INT32(0);
}