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New C function: bms_add_range

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This will be used by pending patches to improve partition pruning.

Amit Langote and Kyotaro Horiguchi, per a suggestion from David
Rowley.  Review and testing of the larger patch set of which this is a
part by Ashutosh Bapat, David Rowley, Dilip Kumar, Jesper Pedersen,
Rajkumar Raghuwanshi, Beena Emerson, Amul Sul, and Kyotaro Horiguchi.

Discussion: http://postgr.es/m/098b9c71-1915-1a2a-8d52-1a7a50ce79e8@lab.ntt.co.jp
This commit is contained in:
Robert Haas 2017-11-29 17:06:14 -05:00
parent 8d4e70a63b
commit 84940644de
2 changed files with 73 additions and 0 deletions
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72
src/backend/nodes/bitmapset.c
View File

@ -784,6 +784,78 @@ bms_add_members(Bitmapset *a, const Bitmapset *b)
return result;
}
/*
* bms_add_range
* Add members in the range of 'lower' to 'upper' to the set.
*
* Note this could also be done by calling bms_add_member in a loop, however,
* using this function will be faster when the range is large as we work with
* at the bitmapword level rather than at bit level.
*/
Bitmapset *
bms_add_range(Bitmapset *a, int lower, int upper)
{
int lwordnum,
lbitnum,
uwordnum,
ushiftbits,
wordnum;
if (lower < 0 || upper < 0)
elog(ERROR, "negative bitmapset member not allowed");
if (lower > upper)
elog(ERROR, "lower range must not be above upper range");
uwordnum = WORDNUM(upper);
if (a == NULL)
{
a = (Bitmapset *) palloc0(BITMAPSET_SIZE(uwordnum + 1));
a->nwords = uwordnum + 1;
}
/* ensure we have enough words to store the upper bit */
else if (uwordnum >= a->nwords)
{
int oldnwords = a->nwords;
int i;
a = (Bitmapset *) repalloc(a, BITMAPSET_SIZE(uwordnum + 1));
a->nwords = uwordnum + 1;
/* zero out the enlarged portion */
for (i = oldnwords; i < a->nwords; i++)
a->words[i] = 0;
}
wordnum = lwordnum = WORDNUM(lower);
lbitnum = BITNUM(lower);
ushiftbits = BITS_PER_BITMAPWORD - (BITNUM(upper) + 1);
/*
* Special case when lwordnum is the same as uwordnum we must perform the
* upper and lower masking on the word.
*/
if (lwordnum == uwordnum)
{
a->words[lwordnum] |= ~(bitmapword) (((bitmapword) 1 << lbitnum) - 1)
& (~(bitmapword) 0) >> ushiftbits;
}
else
{
/* turn on lbitnum and all bits left of it */
a->words[wordnum++] |= ~(bitmapword) (((bitmapword) 1 << lbitnum) - 1);
/* turn on all bits for any intermediate words */
while (wordnum < uwordnum)
a->words[wordnum++] = ~(bitmapword) 0;
/* turn on upper's bit and all bits right of it. */
a->words[uwordnum] |= (~(bitmapword) 0) >> ushiftbits;
}
return a;
}
/*
* bms_int_members - like bms_intersect, but left input is recycled
*/

1
src/include/nodes/bitmapset.h
View File

@ -90,6 +90,7 @@ extern bool bms_is_empty(const Bitmapset *a);
extern Bitmapset *bms_add_member(Bitmapset *a, int x);
extern Bitmapset *bms_del_member(Bitmapset *a, int x);
extern Bitmapset *bms_add_members(Bitmapset *a, const Bitmapset *b);
extern Bitmapset *bms_add_range(Bitmapset *a, int lower, int upper);
extern Bitmapset *bms_int_members(Bitmapset *a, const Bitmapset *b);
extern Bitmapset *bms_del_members(Bitmapset *a, const Bitmapset *b);
extern Bitmapset *bms_join(Bitmapset *a, Bitmapset *b);