Switch to CRC-32C in WAL and other places.

The old algorithm was found to not be the usual CRC-32 algorithm, used by
Ethernet et al. We were using a non-reflected lookup table with code meant
for a reflected lookup table. That's a strange combination that AFAICS does
not correspond to any bit-wise CRC calculation, which makes it difficult to
reason about its properties. Although it has worked well in practice, seems
safer to use a well-known algorithm.

Since we're changing the algorithm anyway, we might as well choose a
different polynomial. The Castagnoli polynomial has better error-correcting
properties than the traditional CRC-32 polynomial, even if we had
implemented it correctly. Another reason for picking that is that some new
CPUs have hardware support for calculating CRC-32C, but not CRC-32, let
alone our strange variant of it. This patch doesn't add any support for such
hardware, but a future patch could now do that.

The old algorithm is kept around for tsquery and pg_trgm, which use the
values in indexes that need to remain compatible so that pg_upgrade works.
While we're at it, share the old lookup table for CRC-32 calculation
between hstore, ltree and core. They all use the same table, so might as
well.

2 files changed, 24 insertions, 24 deletions

diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 5e59c6b819b..71c5fe2490a 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -1517,9 +1517,9 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 	ondisk->magic = SNAPBUILD_MAGIC;
 	ondisk->version = SNAPBUILD_VERSION;
 	ondisk->length = needed_length;
-	INIT_CRC32(ondisk->checksum);
-	COMP_CRC32(ondisk->checksum,
-			   ((char *) ondisk) + SnapBuildOnDiskNotChecksummedSize,
+	INIT_CRC32C(ondisk->checksum);
+	COMP_CRC32C(ondisk->checksum,
+				((char *) ondisk) + SnapBuildOnDiskNotChecksummedSize,
 			SnapBuildOnDiskConstantSize - SnapBuildOnDiskNotChecksummedSize);
 	ondisk_c += sizeof(SnapBuildOnDisk);
 
@@ -1531,20 +1531,20 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 	ondisk->builder.running.xip = NULL;
 	ondisk->builder.committed.xip = NULL;
 
-	COMP_CRC32(ondisk->checksum,
-			   &ondisk->builder,
-			   sizeof(SnapBuild));
+	COMP_CRC32C(ondisk->checksum,
+				&ondisk->builder,
+				sizeof(SnapBuild));
 
 	/* copy running xacts */
 	sz = sizeof(TransactionId) * builder->running.xcnt_space;
 	memcpy(ondisk_c, builder->running.xip, sz);
-	COMP_CRC32(ondisk->checksum, ondisk_c, sz);
+	COMP_CRC32C(ondisk->checksum, ondisk_c, sz);
 	ondisk_c += sz;
 
 	/* copy committed xacts */
 	sz = sizeof(TransactionId) * builder->committed.xcnt;
 	memcpy(ondisk_c, builder->committed.xip, sz);
-	COMP_CRC32(ondisk->checksum, ondisk_c, sz);
+	COMP_CRC32C(ondisk->checksum, ondisk_c, sz);
 	ondisk_c += sz;
 
 	/* we have valid data now, open tempfile and write it there */
@@ -1672,8 +1672,8 @@ SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
 				(errmsg("snapbuild state file \"%s\" has unsupported version %u instead of %u",
 						path, ondisk.version, SNAPBUILD_VERSION)));
 
-	INIT_CRC32(checksum);
-	COMP_CRC32(checksum,
+	INIT_CRC32C(checksum);
+	COMP_CRC32C(checksum,
 			   ((char *) &ondisk) + SnapBuildOnDiskNotChecksummedSize,
 			SnapBuildOnDiskConstantSize - SnapBuildOnDiskNotChecksummedSize);
 
@@ -1687,7 +1687,7 @@ SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
 				 errmsg("could not read file \"%s\", read %d of %d: %m",
 						path, readBytes, (int) sizeof(SnapBuild))));
 	}
-	COMP_CRC32(checksum, &ondisk.builder, sizeof(SnapBuild));
+	COMP_CRC32C(checksum, &ondisk.builder, sizeof(SnapBuild));
 
 	/* restore running xacts information */
 	sz = sizeof(TransactionId) * ondisk.builder.running.xcnt_space;
@@ -1701,7 +1701,7 @@ SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
 				 errmsg("could not read file \"%s\", read %d of %d: %m",
 						path, readBytes, (int) sz)));
 	}
-	COMP_CRC32(checksum, ondisk.builder.running.xip, sz);
+	COMP_CRC32C(checksum, ondisk.builder.running.xip, sz);
 
 	/* restore committed xacts information */
 	sz = sizeof(TransactionId) * ondisk.builder.committed.xcnt;
@@ -1715,12 +1715,12 @@ SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
 				 errmsg("could not read file \"%s\", read %d of %d: %m",
 						path, readBytes, (int) sz)));
 	}
-	COMP_CRC32(checksum, ondisk.builder.committed.xip, sz);
+	COMP_CRC32C(checksum, ondisk.builder.committed.xip, sz);
 
 	CloseTransientFile(fd);
 
 	/* verify checksum of what we've read */
-	if (!EQ_CRC32(checksum, ondisk.checksum))
+	if (!EQ_CRC32C(checksum, ondisk.checksum))
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("snapbuild state file %s: checksum mismatch, is %u, should be %u",
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index f355f13d293..2c3ea555d09 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -993,7 +993,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)
 	}
 
 	cp.magic = SLOT_MAGIC;
-	INIT_CRC32(cp.checksum);
+	INIT_CRC32C(cp.checksum);
 	cp.version = 1;
 	cp.length = ReplicationSlotOnDiskDynamicSize;
 
@@ -1003,9 +1003,9 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)
 
 	SpinLockRelease(&slot->mutex);
 
-	COMP_CRC32(cp.checksum,
-			   (char *) (&cp) + ReplicationSlotOnDiskConstantSize,
-			   ReplicationSlotOnDiskDynamicSize);
+	COMP_CRC32C(cp.checksum,
+				(char *) (&cp) + ReplicationSlotOnDiskConstantSize,
+				ReplicationSlotOnDiskDynamicSize);
 
 	if ((write(fd, &cp, sizeof(cp))) != sizeof(cp))
 	{
@@ -1181,13 +1181,13 @@ RestoreSlotFromDisk(const char *name)
 
 	CloseTransientFile(fd);
 
-	/* now verify the CRC32 */
-	INIT_CRC32(checksum);
-	COMP_CRC32(checksum,
-			   (char *) &cp + ReplicationSlotOnDiskConstantSize,
-			   ReplicationSlotOnDiskDynamicSize);
+	/* now verify the CRC */
+	INIT_CRC32C(checksum);
+	COMP_CRC32C(checksum,
+				(char *) &cp + ReplicationSlotOnDiskConstantSize,
+				ReplicationSlotOnDiskDynamicSize);
 
-	if (!EQ_CRC32(checksum, cp.checksum))
+	if (!EQ_CRC32C(checksum, cp.checksum))
 		ereport(PANIC,
 				(errmsg("replication slot file %s: checksum mismatch, is %u, should be %u",
 						path, checksum, cp.checksum)));