pgsql: BRIN: fix bug in xlog backup block counting

BRIN: fix bug in xlog backup block counting

The code that generates the BRIN_XLOG_UPDATE removes the buffer
reference when the page that's target for the updated tuple is freshly
initialized. This is a pretty usual optimization, but was breaking the
case where the revmap buffer, which is referenced in the same WAL
record, is getting a backup block: the replay code was using backup
block index 1, which is not valid when the update target buffer gets
pruned; the revmap buffer gets assigned 0 instead. Make sure to use the
correct backup block index for revmap when replaying.

Bug reported by Fujii Masao.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/a590f266e44c492d2a252ab9dee0cd88dbe06dc5

Modified Files
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src/backend/access/brin/brin_xlog.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)