external
/
citus
mirror of https://github.com/citusdata/citus.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Re-consider VALID_ITEMPOINTER_OFFSETS wrt bitmap scan logic

pull/5052/head
Onur Tirtir 2021-05-05 02:09:41 +03:00
parent 0f4c97e0d0
commit 4f3c672ebe
1 changed files with 5 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/include/columnar/columnar_tableam.h
View File

@ -18,18 +18,14 @@
* for columnar tables to the following interval:
* [FirstOffsetNumber, MaxOffsetNumber].
*
* However, for GIN indexes, Postgres also asserts the following in
* itemptr_to_uint64 function:
* "GinItemPointerGetOffsetNumber(iptr) < (1 << MaxHeapTuplesPerPageBits)",
* where MaxHeapTuplesPerPageBits = 11.
* That means, offsetNumber for columnar tables can't be equal to
* 2**11 = 2048 = MaxOffsetNumber.
* Hence we can't use MaxOffsetNumber as offsetNumber too.
* However, bitmap scan logic assumes that itemPointer.offsetNumber cannot
* be larger than MaxHeapTuplesPerPage (see tbm_add_tuples).
*
* For this reason, we restrict itemPointer.offsetNumber
* to the following interval: [FirstOffsetNumber, MaxOffsetNumber).
* to the following interval: [FirstOffsetNumber, MaxHeapTuplesPerPage].
*/
#define VALID_ITEMPOINTER_OFFSETS ((uint64) (MaxOffsetNumber - FirstOffsetNumber))
#define VALID_ITEMPOINTER_OFFSETS \
((uint64) (MaxHeapTuplesPerPage - FirstOffsetNumber + 1))
/*
* Number of valid ItemPointer BlockNumber's for "row number" <> "ItemPointer"