On Wed, Jan 4, 2012 at 1:35 PM, Kevin Grittner
<[email protected]> wrote:
> Simon Riggs wrote:
>
>> My focus was on getting something working first, then tuning. If
>> we're agreed that we have everything apart from the tuning then we
>> can proceed with tests to see which works better.
>
> Sure. I just think you are there already except for what I got into.
>
> FWIW, moving the modulus application out of the loop is a very
> trivial change and has no affect on the results; it's strictly a
> performance issue.
New version attached, with your suggested changes included. Hole check
code is there as well, but ifdef'd out since it isn't a valid check in
all cases.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0cc3296..9b367a3 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1701,6 +1701,48 @@ SET ENABLE_SEQSCAN TO OFF;
</listitem>
</varlistentry>
+ <varlistentry id="guc-page-checksums" xreflabel="page_checksums">
+ <indexterm>
+ <primary><varname>page_checksums</> configuration parameter</primary>
+ </indexterm>
+ <term><varname>page_checksums</varname> (<type>boolean</type>)</term>
+ <listitem>
+ <para>
+ When this parameter is on, the <productname>PostgreSQL</> server
+ calculates checksums when it writes main database pages to disk,
+ flagging the page as checksum protected. When this parameter is off,
+ no checksum is written, only a standard watermark in the page header.
+ The database may thus contain a mix of pages with checksums and pages
+ without checksums.
+ </para>
+
+ <para>
+ When pages are read into shared buffers any page flagged with a
+ checksum has the checksum re-calculated and compared against the
+ stored value to provide greatly improved validation of page contents.
+ </para>
+
+ <para>
+ Writes via temp_buffers are not checksummed.
+ </para>
+
+ <para>
+ Turning this parameter off speeds normal operation, but
+ might allow data corruption to go unnoticed. The checksum uses
+ 16-bit checksums, using the fast Fletcher 16 algorithm. With this
+ parameter enabled there is still a non-zero probability that an error
+ could go undetected, as well as a non-zero probability of false
+ positives.
+ </para>
+
+ <para>
+ This parameter can only be set in the <filename>postgresql.conf</>
+ file or on the server command line.
+ The default is <literal>off</>.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-wal-buffers" xreflabel="wal_buffers">
<term><varname>wal_buffers</varname> (<type>integer</type>)</term>
<indexterm>
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 91cc001..a43b7be 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -440,7 +440,7 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
smgrread(smgr, forkNum, blockNum, (char *) bufBlock);
/* check for garbage data */
- if (!PageHeaderIsValid((PageHeader) bufBlock))
+ if (!PageIsVerified((Page) bufBlock))
{
if (mode == RBM_ZERO_ON_ERROR || zero_damaged_pages)
{
@@ -1860,6 +1860,8 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
{
XLogRecPtr recptr;
ErrorContextCallback errcontext;
+ Block bufBlock;
+ char *bufCopy;
/*
* Acquire the buffer's io_in_progress lock. If StartBufferIO returns
@@ -1907,10 +1909,24 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
buf->flags &= ~BM_JUST_DIRTIED;
UnlockBufHdr(buf);
+ /*
+ * Set page verification info immediately before we write the buffer to disk.
+ * Once we have flushed the buffer is marked clean again, meaning it can
+ * be replaced quickly and silently with another data block, so we must
+ * write verification info now. For efficiency, the process of cleaning
+ * and page replacement is asynchronous, so we can't do this *only* when
+ * we are about to replace the buffer, we need to do this for every flush.
+ */
+ bufBlock = BufHdrGetBlock(buf);
+ bufCopy = PageSetVerificationInfo((Page) bufBlock);
+
+ /*
+ * bufToWrite is either the shared buffer or a copy, as appropriate.
+ */
smgrwrite(reln,
buf->tag.forkNum,
buf->tag.blockNum,
- (char *) BufHdrGetBlock(buf),
+ (char *) bufCopy,
false);
pgBufferUsage.shared_blks_written++;
@@ -1921,6 +1937,8 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
*/
TerminateBufferIO(buf, true, 0);
+ /* XXX Assert(buf is not BM_JUST_DIRTIED) */
+
TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(buf->tag.forkNum,
buf->tag.blockNum,
reln->smgr_rnode.node.spcNode,
diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c
index 096d36a..a220310 100644
--- a/src/backend/storage/buffer/localbuf.c
+++ b/src/backend/storage/buffer/localbuf.c
@@ -200,6 +200,8 @@ LocalBufferAlloc(SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum,
/* Find smgr relation for buffer */
oreln = smgropen(bufHdr->tag.rnode, MyBackendId);
+ /* XXX do we want to write checksums for local buffers? An option? */
+
/* And write... */
smgrwrite(oreln,
bufHdr->tag.forkNum,
diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c
index 90a731c..c49c2e1 100644
--- a/src/backend/storage/page/bufpage.c
+++ b/src/backend/storage/page/bufpage.c
@@ -16,6 +16,12 @@
#include "access/htup.h"
+bool page_checksums = false;
+
+static char pageCopy[BLCKSZ]; /* temporary buffer to allow checksum calculation */
+
+static bool PageVerificationInfoOK(Page page);
+static uint16 PageCalcChecksum16(Page page);
/* ----------------------------------------------------------------
* Page support functions
@@ -25,6 +31,10 @@
/*
* PageInit
* Initializes the contents of a page.
+ * Note that we don't automatically add a checksum, or flag that the
+ * page has a checksum field. We start with a normal page layout and defer
+ * the decision on what page verification will be written just before
+ * we write the block to disk.
*/
void
PageInit(Page page, Size pageSize, Size specialSize)
@@ -67,20 +77,20 @@ PageInit(Page page, Size pageSize, Size specialSize)
* will clean up such a page and make it usable.
*/
bool
-PageHeaderIsValid(PageHeader page)
+PageIsVerified(Page page)
{
+ PageHeader p = (PageHeader) page;
char *pagebytes;
int i;
/* Check normal case */
- if (PageGetPageSize(page) == BLCKSZ &&
- PageGetPageLayoutVersion(page) == PG_PAGE_LAYOUT_VERSION &&
- (page->pd_flags & ~PD_VALID_FLAG_BITS) == 0 &&
- page->pd_lower >= SizeOfPageHeaderData &&
- page->pd_lower <= page->pd_upper &&
- page->pd_upper <= page->pd_special &&
- page->pd_special <= BLCKSZ &&
- page->pd_special == MAXALIGN(page->pd_special))
+ if (PageVerificationInfoOK(page) &&
+ (p->pd_flags & ~PD_VALID_FLAG_BITS) == 0 &&
+ p->pd_lower >= SizeOfPageHeaderData &&
+ p->pd_lower <= p->pd_upper &&
+ p->pd_upper <= p->pd_special &&
+ p->pd_special <= BLCKSZ &&
+ p->pd_special == MAXALIGN(p->pd_special))
return true;
/* Check all-zeroes case */
@@ -93,7 +103,6 @@ PageHeaderIsValid(PageHeader page)
return true;
}
-
/*
* PageAddItem
*
@@ -827,3 +836,239 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
pfree(itemidbase);
}
+
+/*
+ * Test whether the page verification information is correct or not.
+ *
+ * IMPORTANT NOTE -
+ * Verification info is not valid at all times on a data page. We set
+ * verification info before we flush page/buffer, and implicitly invalidate
+ * verification info when we write to the page. A heavily accessed buffer
+ * might then spend most of its life with invalid page verification info,
+ * so testing verification info on random pages in the buffer pool will tell
+ * you nothing. The reason for this is that page verification info protects
+ * Postgres data from errors on the filesystems on which we rely. We do not
+ * protect buffers against uncorrectable memory errors, since these have a
+ * very low measured incidence according to research on large server farms,
+ * http://www.google.com/research/pubs/archive/35162.pdf, discussed 2010/12/22.
+ *
+ * To confirm your understanding that means that WAL-logged changes to a page
+ * do NOT update the page verification info, so full page images may not have
+ * correct verification information on them. But those page images have the
+ * WAL CRC covering them and so are verified separately from this mechanism.
+ * WAL replay ignores page verification info unless it writes out or reads in
+ * blocks from disk; restoring full page writes does not check verification
+ * info via this function.
+ *
+ * The best way to understand this is that WAL CRCs protect records entering
+ * the WAL stream, and page verification protects blocks entering and leaving
+ * the buffer pool. They are similar in purpose, yet completely separate.
+ * Together they ensure we are able to detect errors in data leaving and
+ * re-entering PostgreSQL controlled memory.
+ *
+ * Note also that the verification mechanism can vary from page to page.
+ * All we do here is look at what the page itself says is the verification
+ * mechanism and then apply that test. This allows us to run without the CPU
+ * cost of verification if we choose, as well as to provide an upgrade path
+ * for anyone doing direct upgrades using pg_upgrade.
+ *
+ * There is some concern that trusting page data to say how to check page
+ * data is dangerously self-referential. To ensure no mistakes we set two
+ * non-adjacent bits to signify that the page has a checksum and
+ * should be verified when that block is read back into a buffer.
+ * We use two bits in case a multiple bit error removes one of the checksum
+ * flags *and* destroys data, which would lead to skipping the checksum check
+ * and silently accepting bad data.
+ *
+ * Note also that this returns a boolean, not a full damage assessment.
+ */
+static bool
+PageVerificationInfoOK(Page page)
+{
+ PageHeader p = (PageHeader) page;
+
+ /*
+ * We set two non-adjacent bits to signify that the page has a checksum and
+ * should be verified against that block is read back into a buffer.
+ * We use two bits in case a multiple bit error removes one of the checksum
+ * flags and destroys data, which would lead to skipping the checksum check
+ * and silently accepting bad data.
+ */
+ if (PageHasChecksumFlag1(p) && PageHasChecksumFlag2(p))
+ {
+ uint16 checksum = PageCalcChecksum16(page);
+
+ if (checksum == p->pd_verify.pd_checksum16)
+ {
+#ifdef CHECK_HOLE
+ /* Also check page hole is all-zeroes */
+ char *pagebytes;
+ bool empty = true;
+ int i;
+
+ pagebytes = (char *) page;
+ for (i = p->pd_lower; i < p->pd_upper; i++)
+ {
+ if (pagebytes[i] != 0)
+ {
+ empty = false;
+ break;
+ }
+ }
+
+ if (!empty)
+ elog(LOG, "hole was not empty at byte %d pd_lower %d pd_upper %d",
+ i, p->pd_lower, p->pd_upper);
+#endif
+ return true;
+ }
+
+ elog(LOG, "page verification failed - checksum was %u page checksum field is %u",
+ checksum, p->pd_verify.pd_checksum16);
+ }
+ else if (!PageHasChecksumFlag1(p) && !PageHasChecksumFlag2(p))
+ {
+ if (PageGetPageLayoutVersion(p) == PG_PAGE_LAYOUT_VERSION &&
+ PageGetPageSize(p) == BLCKSZ)
+ return true;
+ }
+ else
+ elog(LOG, "page verification failed - page has one checksum flag set");
+
+ return false;
+}
+
+/*
+ * Set verification info for page.
+ *
+ * Either we set a new checksum, or we set the standard watermark. We must
+ * not leave an invalid checksum in place. Note that the verification info is
+ * not WAL logged, whereas the data changes to pages are, so data is safe
+ * whether or not we have page_checksums enabled. The purpose of checksums
+ * is to detect page corruption to allow replacement from backup.
+ *
+ * Returns a pointer to the block-sized data that needs to be written. That
+ * allows us to either copy, or not, depending upon whether we checksum.
+ */
+char *
+PageSetVerificationInfo(Page page)
+{
+ PageHeader p;
+
+ if (PageIsNew(page))
+ return (char *) page;
+
+ if (page_checksums)
+ {
+ /*
+ * We make a copy iff we need to calculate a checksum because other
+ * backends may set hint bits on this page while we write, which
+ * would mean the checksum differs from the page contents. It doesn't
+ * matter if we include or exclude hints during the copy, as long
+ * as we write a valid page and associated checksum.
+ */
+ memcpy(&pageCopy, page, BLCKSZ);
+
+ p = (PageHeader) &pageCopy;
+ p->pd_flags |= PD_CHECKSUM;
+ p->pd_verify.pd_checksum16 = PageCalcChecksum16((Page) &pageCopy);
+
+ return (char *) &pageCopy;
+ }
+
+ p = (PageHeader) page;
+
+ if (PageHasChecksumFlag1(p) || PageHasChecksumFlag2(p))
+ {
+ /* ensure any older checksum info is overwritten with watermark */
+ p->pd_flags &= ~PD_CHECKSUM;
+ PageSetPageSizeAndVersion(p, BLCKSZ, PG_PAGE_LAYOUT_VERSION);
+ }
+
+ return (char *) page;
+}
+
+/*
+ * Calculate checksum for a PostgreSQL Page. We do this in 3 steps, first
+ * we calculate the checksum for the header, avoiding the verification
+ * info, which will be added afterwards. Next, we add the line pointers up to
+ * the hole in the middle of the block at pd_lower. Last, we add the tail
+ * of the page from pd_upper to the end of page.
+ */
+static uint16
+PageCalcChecksum16(Page page)
+{
+#define PAGE_VERIFICATION_USES_FLETCHER16 (true)
+#ifdef PAGE_VERIFICATION_USES_FLETCHER16
+ /*
+ * Following calculation is a Flecther's 16 checksum. The calc is isolated
+ * here and tuning and/or replacement algorithms are possible.
+ *
+ * XXX present implementation is raw, untuned calculation, please tweak
+ */
+ PageHeader p = (PageHeader) page;
+ uint page_header_stop = (uint)(offsetof(PageHeaderData, pd_special) + sizeof(LocationIndex));
+ uint page_lower_start = (uint)(offsetof(PageHeaderData, pd_prune_xid));
+ uint page_lower_stop;
+ uint sum1 = 0;
+ uint64 sum2 = 0;
+ int i;
+
+ /*
+ * Avoid calculating checksum if page is new, just return a value that
+ * will cause the check to fail. We may still pass the all-zeroes check.
+ */
+ if (PageIsNew(page))
+ return 1;
+
+ /*
+ * Just add in the pd_prune_xid if there are no line pointers yet.
+ */
+ page_lower_stop = p->pd_lower;
+ if (page_lower_stop == 0)
+ page_lower_stop = page_lower_start + sizeof(TransactionId);
+
+ Assert(p->pd_upper != 0);
+
+#ifdef DEBUG_CHECKSUM
+ elog(LOG, "calculating checksum for %u-%u %u-%u %u-%u",
+ 0, /* page_header_start */
+ page_header_stop,
+ page_lower_start,
+ page_lower_stop,
+ p->pd_upper,
+ BLCKSZ
+ );
+#endif
+
+#define COMP_F16(from, to) \
+do { \
+ for (i = from; i < to; i++) \
+ { \
+ sum1 = sum1 + page[i]; \
+ sum2 = sum1 + sum2; \
+ } \
+ sum1 %= 255; \
+ sum2 %= 255; \
+} while (0); \
+
+ COMP_F16(0,
+ page_header_stop);
+
+ /* ignore the checksum field since not done yet... */
+
+ COMP_F16(page_lower_start,
+ page_lower_stop);
+
+ /* ignore the hole in the middle of the block */
+
+ COMP_F16(p->pd_upper,
+ BLCKSZ - 1);
+
+#ifdef DEBUG_CHECKSUM
+ elog(LOG, "checksum %u", ((sum2 << 8) | sum1));
+#endif
+
+ return ((sum2 << 8) | sum1);
+#endif
+}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 5c910dd..e868280 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -830,6 +830,20 @@ static struct config_bool ConfigureNamesBool[] =
NULL, NULL, NULL
},
{
+ {"page_checksums", PGC_SIGHUP, WAL_SETTINGS,
+ gettext_noop("Marks database blocks with a checksum before writing them to disk. "),
+ gettext_noop("When enabled all database blocks will be marked with a checksums before writing to disk. "
+ "When we read a database block from disk the checksum is checked, if it exists. "
+ "If there is no checksum marked yet then no check is performed, though a "
+ "checksum will be added later when we re-write the database block. "
+ "When disabled checksums will be ignored, even if the block was marked "
+ "with checksum. When disabled checksums will not be added to database blocks.")
+ },
+ &page_checksums,
+ true,
+ NULL, NULL, NULL
+ },
+ {
{"full_page_writes", PGC_SIGHUP, WAL_SETTINGS,
gettext_noop("Writes full pages to WAL when first modified after a checkpoint."),
gettext_noop("A page write in process during an operating system crash might be "
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 315db46..6f81023 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -150,15 +150,21 @@
#------------------------------------------------------------------------------
-# WRITE AHEAD LOG
+# WRITE AHEAD LOG & RELIABILITY
#------------------------------------------------------------------------------
-# - Settings -
+# - Reliability -
-#wal_level = minimal # minimal, archive, or hot_standby
- # (change requires restart)
+#page_checksums = off # calculate checksum before database I/O
+#full_page_writes = on # recover from partial page writes
#fsync = on # turns forced synchronization on or off
+
#synchronous_commit = on # synchronization level; on, off, or local
+
+# - Write Ahead Log -
+
+#wal_level = minimal # minimal, archive, or hot_standby
+ # (change requires restart)
#wal_sync_method = fsync # the default is the first option
# supported by the operating system:
# open_datasync
@@ -166,7 +172,6 @@
# fsync
# fsync_writethrough
# open_sync
-#full_page_writes = on # recover from partial page writes
#wal_buffers = -1 # min 32kB, -1 sets based on shared_buffers
# (change requires restart)
#wal_writer_delay = 200ms # 1-10000 milliseconds
diff --git a/src/include/storage/bufpage.h b/src/include/storage/bufpage.h
index 1ab64e0..dab9189 100644
--- a/src/include/storage/bufpage.h
+++ b/src/include/storage/bufpage.h
@@ -18,6 +18,8 @@
#include "storage/item.h"
#include "storage/off.h"
+extern bool page_checksums;
+
/*
* A postgres disk page is an abstraction layered on top of a postgres
* disk block (which is simply a unit of i/o, see block.h).
@@ -93,7 +95,7 @@ typedef uint16 LocationIndex;
* pd_lower - offset to start of free space.
* pd_upper - offset to end of free space.
* pd_special - offset to start of special space.
- * pd_pagesize_version - size in bytes and page layout version number.
+ * pd_verify - page verification information of different kinds
* pd_prune_xid - oldest XID among potentially prunable tuples on page.
*
* The LSN is used by the buffer manager to enforce the basic rule of WAL:
@@ -106,7 +108,8 @@ typedef uint16 LocationIndex;
* pd_prune_xid is a hint field that helps determine whether pruning will be
* useful. It is currently unused in index pages.
*
- * The page version number and page size are packed together into a single
+ * For verification we store either a 16 bit checksum or a watermark of
+ * the page version number and page size packed together into a single
* uint16 field. This is for historical reasons: before PostgreSQL 7.3,
* there was no concept of a page version number, and doing it this way
* lets us pretend that pre-7.3 databases have page version number zero.
@@ -130,7 +133,13 @@ typedef struct PageHeaderData
LocationIndex pd_lower; /* offset to start of free space */
LocationIndex pd_upper; /* offset to end of free space */
LocationIndex pd_special; /* offset to start of special space */
- uint16 pd_pagesize_version;
+
+ union
+ {
+ uint16 pd_pagesize_version;
+ uint16 pd_checksum16;
+ } pd_verify; /* page verification data */
+
TransactionId pd_prune_xid; /* oldest prunable XID, or zero if none */
ItemIdData pd_linp[1]; /* beginning of line pointer array */
} PageHeaderData;
@@ -155,7 +164,16 @@ typedef PageHeaderData *PageHeader;
#define PD_ALL_VISIBLE 0x0004 /* all tuples on page are visible to
* everyone */
-#define PD_VALID_FLAG_BITS 0x0007 /* OR of all valid pd_flags bits */
+#define PD_VALID_FLAG_BITS 0x800F /* OR of all non-checksum pd_flags bits */
+
+#define PD_CHECKSUM1 0x0008 /* First checksum bit */
+#define PD_CHECKSUM2 0x8000 /* Second checksum bit */
+#define PD_CHECKSUM 0x8008 /* OR of both checksum flags */
+
+#define PageHasChecksumFlag1(page) \
+ ((((PageHeader) (page))->pd_flags & PD_CHECKSUM1) == PD_CHECKSUM1)
+#define PageHasChecksumFlag2(page) \
+ ((((PageHeader) (page))->pd_flags & PD_CHECKSUM2) == PD_CHECKSUM2)
/*
* Page layout version number 0 is for pre-7.3 Postgres releases.
@@ -165,6 +183,8 @@ typedef PageHeaderData *PageHeader;
* Release 8.3 uses 4; it changed the HeapTupleHeader layout again, and
* added the pd_flags field (by stealing some bits from pd_tli),
* as well as adding the pd_prune_xid field (which enlarges the header).
+ * Release 9.2 uses 4 as well, though with changed meaning of verification bits.
+ * We deliberately don't bump the page version for that, to allow upgrades.
*/
#define PG_PAGE_LAYOUT_VERSION 4
@@ -231,19 +251,22 @@ typedef PageHeaderData *PageHeader;
* PageGetPageSize
* Returns the page size of a page.
*
- * this can only be called on a formatted page (unlike
- * BufferGetPageSize, which can be called on an unformatted page).
- * however, it can be called on a page that is not stored in a buffer.
+ * Since PageSizeIsValid() when pagesize == BLCKSZ, just written BLCKSZ.
+ * This can be called on any page, initialised or not, in or out of buffers.
+ * You might think this can vary at runtime but you'd be wrong, since pages
+ * frequently need to occupy buffers and pages are copied from one to another
+ * so there are many hidden assumptions that this simple definition is true.
*/
-#define PageGetPageSize(page) \
- ((Size) (((PageHeader) (page))->pd_pagesize_version & (uint16) 0xFF00))
+#define PageGetPageSize(page) (BLCKSZ)
/*
* PageGetPageLayoutVersion
* Returns the page layout version of a page.
+ *
+ * Must not be used on a page that is flagged for checksums.
*/
#define PageGetPageLayoutVersion(page) \
- (((PageHeader) (page))->pd_pagesize_version & 0x00FF)
+ (((PageHeader) (page))->pd_verify.pd_pagesize_version & 0x00FF)
/*
* PageSetPageSizeAndVersion
@@ -251,12 +274,14 @@ typedef PageHeaderData *PageHeader;
*
* We could support setting these two values separately, but there's
* no real need for it at the moment.
+ *
+ * Must not be used on a page that is flagged for checksums.
*/
#define PageSetPageSizeAndVersion(page, size, version) \
( \
AssertMacro(((size) & 0xFF00) == (size)), \
AssertMacro(((version) & 0x00FF) == (version)), \
- ((PageHeader) (page))->pd_pagesize_version = (size) | (version) \
+ ((PageHeader) (page))->pd_verify.pd_pagesize_version = (size) | (version) \
)
/* ----------------
@@ -368,7 +393,7 @@ do { \
*/
extern void PageInit(Page page, Size pageSize, Size specialSize);
-extern bool PageHeaderIsValid(PageHeader page);
+extern bool PageIsVerified(Page page);
extern OffsetNumber PageAddItem(Page page, Item item, Size size,
OffsetNumber offsetNumber, bool overwrite, bool is_heap);
extern Page PageGetTempPage(Page page);
@@ -381,5 +406,6 @@ extern Size PageGetExactFreeSpace(Page page);
extern Size PageGetHeapFreeSpace(Page page);
extern void PageIndexTupleDelete(Page page, OffsetNumber offset);
extern void PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems);
+extern char *PageSetVerificationInfo(Page page);
#endif /* BUFPAGE_H */
--
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