Hi Hackers,
After the subtransaction had been added,
the size of HeapTupleHeader became 27 bytes.
This consumes extra bytes per tuple for the alignment padding,
especially on systems where MAXIMUM_ALIGNOF is 8.
This patch optimizes the location of the first field,
and reduces the padding. I expect most rows are saved
about 4 bytes, if the table definition is appropriate.
Following is a bit artificial test:
# CREATE TABLE test (c "char", i int4);
# INSERT INTO test VALUES('A', 1);
# SELECT * FROM pgstattuple('test');
the size of a tuple (8.1.0) is 40 bytes:
[27] HeapTupleHeader
[ 5] (padding)
[ 1] c "char"
[ 3] (padding)
[ 4] i int4
the size of tuple (patched) is 32 bytes
[27] HeapTupleHeader
[ 1] c "char"
[ 4] i int4
Is this effective? Or are there some problems?
I'll appreciate any comments.
Thanks,
---
ITAGAKI Takahiro
NTT Cyber Space Laboratories
