Allow I/O reliability checks using 16-bit checksums

Checksums are set immediately prior to flush out of shared buffers
and checked when pages are read in again. Hint bit setting will
require full page write when block is dirtied, which causes various
infrastructure changes. Extensive comments, docs and README.

WARNING message thrown if checksum fails on non-all zeroes page;
ERROR thrown but can be disabled with ignore_checksum_failure = on.

Feature enabled by an initdb option, since transition from option off
to option on is long and complex and has not yet been implemented.
Default is not to use checksums.

Checksum used is WAL CRC-32 truncated to 16-bits.

Simon Riggs, Jeff Davis, Greg Smith
Wide input and assistance from many community members. Thank you.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index f2c9ff2e1c1..24384b49890 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -6,7 +6,7 @@
  * NOTE: all the HeapTupleSatisfies routines will update the tuple's
  * "hint" status bits if we see that the inserting or deleting transaction
  * has now committed or aborted (and it is safe to set the hint bits).
- * If the hint bits are changed, SetBufferCommitInfoNeedsSave is called on
+ * If the hint bits are changed, MarkBufferDirtyHint is called on
  * the passed-in buffer.  The caller must hold not only a pin, but at least
  * shared buffer content lock on the buffer containing the tuple.
  *
@@ -121,7 +121,7 @@ SetHintBits(HeapTupleHeader tuple, Buffer buffer,
 	}
 
 	tuple->t_infomask |= infomask;
-	SetBufferCommitInfoNeedsSave(buffer);
+	MarkBufferDirtyHint(buffer);
 }
 
 /*