1 files changed, 323 insertions, 0 deletions
diff --git a/contrib/pageinspect/rawpage.c b/contrib/pageinspect/rawpage.c
new file mode 100644
index 0000000..c018150
--- /dev/null
+++ b/contrib/pageinspect/rawpage.c
@@ -0,0 +1,323 @@
+/*-------------------------------------------------------------------------
+ *
+ * rawpage.c
+ *	  Functions to extract a raw page as bytea and inspect it
+ *
+ * Access-method specific inspection functions are in separate files.
+ *
+ * Copyright (c) 2007-2020, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  contrib/pageinspect/rawpage.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "access/relation.h"
+#include "catalog/namespace.h"
+#include "catalog/pg_type.h"
+#include "funcapi.h"
+#include "miscadmin.h"
+#include "pageinspect.h"
+#include "storage/bufmgr.h"
+#include "storage/checksum.h"
+#include "utils/builtins.h"
+#include "utils/pg_lsn.h"
+#include "utils/rel.h"
+#include "utils/varlena.h"
+
+PG_MODULE_MAGIC;
+
+static bytea *get_raw_page_internal(text *relname, ForkNumber forknum,
+									BlockNumber blkno);
+
+
+/*
+ * get_raw_page
+ *
+ * Returns a copy of a page from shared buffers as a bytea
+ */
+PG_FUNCTION_INFO_V1(get_raw_page);
+
+Datum
+get_raw_page(PG_FUNCTION_ARGS)
+{
+	text	   *relname = PG_GETARG_TEXT_PP(0);
+	uint32		blkno = PG_GETARG_UINT32(1);
+	bytea	   *raw_page;
+
+	/*
+	 * We don't normally bother to check the number of arguments to a C
+	 * function, but here it's needed for safety because early 8.4 beta
+	 * releases mistakenly redefined get_raw_page() as taking three arguments.
+	 */
+	if (PG_NARGS() != 2)
+		ereport(ERROR,
+				(errmsg("wrong number of arguments to get_raw_page()"),
+				 errhint("Run the updated pageinspect.sql script.")));
+
+	raw_page = get_raw_page_internal(relname, MAIN_FORKNUM, blkno);
+
+	PG_RETURN_BYTEA_P(raw_page);
+}
+
+/*
+ * get_raw_page_fork
+ *
+ * Same, for any fork
+ */
+PG_FUNCTION_INFO_V1(get_raw_page_fork);
+
+Datum
+get_raw_page_fork(PG_FUNCTION_ARGS)
+{
+	text	   *relname = PG_GETARG_TEXT_PP(0);
+	text	   *forkname = PG_GETARG_TEXT_PP(1);
+	uint32		blkno = PG_GETARG_UINT32(2);
+	bytea	   *raw_page;
+	ForkNumber	forknum;
+
+	forknum = forkname_to_number(text_to_cstring(forkname));
+
+	raw_page = get_raw_page_internal(relname, forknum, blkno);
+
+	PG_RETURN_BYTEA_P(raw_page);
+}
+
+/*
+ * workhorse
+ */
+static bytea *
+get_raw_page_internal(text *relname, ForkNumber forknum, BlockNumber blkno)
+{
+	bytea	   *raw_page;
+	RangeVar   *relrv;
+	Relation	rel;
+	char	   *raw_page_data;
+	Buffer		buf;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use raw page functions")));
+
+	relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+	rel = relation_openrv(relrv, AccessShareLock);
+
+	/* Check that this relation has storage */
+	if (rel->rd_rel->relkind == RELKIND_VIEW)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("cannot get raw page from view \"%s\"",
+						RelationGetRelationName(rel))));
+	if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("cannot get raw page from composite type \"%s\"",
+						RelationGetRelationName(rel))));
+	if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("cannot get raw page from foreign table \"%s\"",
+						RelationGetRelationName(rel))));
+	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("cannot get raw page from partitioned table \"%s\"",
+						RelationGetRelationName(rel))));
+	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("cannot get raw page from partitioned index \"%s\"",
+						RelationGetRelationName(rel))));
+
+	/*
+	 * Reject attempts to read non-local temporary relations; we would be
+	 * likely to get wrong data since we have no visibility into the owning
+	 * session's local buffers.
+	 */
+	if (RELATION_IS_OTHER_TEMP(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot access temporary tables of other sessions")));
+
+	if (blkno >= RelationGetNumberOfBlocksInFork(rel, forknum))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("block number %u is out of range for relation \"%s\"",
+						blkno, RelationGetRelationName(rel))));
+
+	/* Initialize buffer to copy to */
+	raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);
+	SET_VARSIZE(raw_page, BLCKSZ + VARHDRSZ);
+	raw_page_data = VARDATA(raw_page);
+
+	/* Take a verbatim copy of the page */
+
+	buf = ReadBufferExtended(rel, forknum, blkno, RBM_NORMAL, NULL);
+	LockBuffer(buf, BUFFER_LOCK_SHARE);
+
+	memcpy(raw_page_data, BufferGetPage(buf), BLCKSZ);
+
+	LockBuffer(buf, BUFFER_LOCK_UNLOCK);
+	ReleaseBuffer(buf);
+
+	relation_close(rel, AccessShareLock);
+
+	return raw_page;
+}
+
+
+/*
+ * get_page_from_raw
+ *
+ * Get a palloc'd, maxalign'ed page image from the result of get_raw_page()
+ *
+ * On machines with MAXALIGN = 8, the payload of a bytea is not maxaligned,
+ * since it will start 4 bytes into a palloc'd value.  On alignment-picky
+ * machines, this will cause failures in accesses to 8-byte-wide values
+ * within the page.  We don't need to worry if accessing only 4-byte or
+ * smaller fields, but when examining a struct that contains 8-byte fields,
+ * use this function for safety.
+ */
+Page
+get_page_from_raw(bytea *raw_page)
+{
+	Page		page;
+	int			raw_page_size;
+
+	raw_page_size = VARSIZE_ANY_EXHDR(raw_page);
+
+	if (raw_page_size != BLCKSZ)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid page size"),
+				 errdetail("Expected %d bytes, got %d.",
+						   BLCKSZ, raw_page_size)));
+
+	page = palloc(raw_page_size);
+
+	memcpy(page, VARDATA_ANY(raw_page), raw_page_size);
+
+	return page;
+}
+
+
+/*
+ * page_header
+ *
+ * Allows inspection of page header fields of a raw page
+ */
+
+PG_FUNCTION_INFO_V1(page_header);
+
+Datum
+page_header(PG_FUNCTION_ARGS)
+{
+	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
+	int			raw_page_size;
+
+	TupleDesc	tupdesc;
+
+	Datum		result;
+	HeapTuple	tuple;
+	Datum		values[9];
+	bool		nulls[9];
+
+	PageHeader	page;
+	XLogRecPtr	lsn;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use raw page functions")));
+
+	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
+
+	/*
+	 * Check that enough data was supplied, so that we don't try to access
+	 * fields outside the supplied buffer.
+	 */
+	if (raw_page_size < SizeOfPageHeaderData)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("input page too small (%d bytes)", raw_page_size)));
+
+	page = (PageHeader) VARDATA(raw_page);
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	/* Extract information from the page header */
+
+	lsn = PageGetLSN(page);
+
+	/* pageinspect >= 1.2 uses pg_lsn instead of text for the LSN field. */
+	if (TupleDescAttr(tupdesc, 0)->atttypid == TEXTOID)
+	{
+		char		lsnchar[64];
+
+		snprintf(lsnchar, sizeof(lsnchar), "%X/%X",
+				 (uint32) (lsn >> 32), (uint32) lsn);
+		values[0] = CStringGetTextDatum(lsnchar);
+	}
+	else
+		values[0] = LSNGetDatum(lsn);
+	values[1] = UInt16GetDatum(page->pd_checksum);
+	values[2] = UInt16GetDatum(page->pd_flags);
+	values[3] = UInt16GetDatum(page->pd_lower);
+	values[4] = UInt16GetDatum(page->pd_upper);
+	values[5] = UInt16GetDatum(page->pd_special);
+	values[6] = UInt16GetDatum(PageGetPageSize(page));
+	values[7] = UInt16GetDatum(PageGetPageLayoutVersion(page));
+	values[8] = TransactionIdGetDatum(page->pd_prune_xid);
+
+	/* Build and return the tuple. */
+
+	memset(nulls, 0, sizeof(nulls));
+
+	tuple = heap_form_tuple(tupdesc, values, nulls);
+	result = HeapTupleGetDatum(tuple);
+
+	PG_RETURN_DATUM(result);
+}
+
+/*
+ * page_checksum
+ *
+ * Compute checksum of a raw page
+ */
+
+PG_FUNCTION_INFO_V1(page_checksum);
+
+Datum
+page_checksum(PG_FUNCTION_ARGS)
+{
+	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
+	uint32		blkno = PG_GETARG_INT32(1);
+	int			raw_page_size;
+	PageHeader	page;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use raw page functions")));
+
+	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
+
+	/*
+	 * Check that the supplied page is of the right size.
+	 */
+	if (raw_page_size != BLCKSZ)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("incorrect size of input page (%d bytes)", raw_page_size)));
+
+	page = (PageHeader) VARDATA(raw_page);
+
+	PG_RETURN_INT16(pg_checksum_page((char *) page, blkno));
+}