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db_include/access/brin_page.h

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+/*
+ * brin_page.h
+ *		Prototypes and definitions for BRIN page layouts
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *		src/include/access/brin_page.h
+ *
+ * NOTES
+ *
+ * These structs should really be private to specific BRIN files, but it's
+ * useful to have them here so that they can be used by pageinspect and similar
+ * tools.
+ */
+#ifndef BRIN_PAGE_H
+#define BRIN_PAGE_H
+
+#include "storage/block.h"
+#include "storage/itemptr.h"
+
+/*
+ * Special area of BRIN pages.
+ *
+ * We define it in this odd way so that it always occupies the last
+ * MAXALIGN-sized element of each page.
+ */
+typedef struct BrinSpecialSpace
+{
+	uint16		vector[MAXALIGN(1) / sizeof(uint16)];
+} BrinSpecialSpace;
+
+/*
+ * Make the page type be the last half-word in the page, for consumption by
+ * pg_filedump and similar utilities.  We don't really care much about the
+ * position of the "flags" half-word, but it's simpler to apply a consistent
+ * rule to both.
+ *
+ * See comments above GinPageOpaqueData.
+ */
+#define BrinPageType(page)		\
+	(((BrinSpecialSpace *)		\
+	  PageGetSpecialPointer(page))->vector[MAXALIGN(1) / sizeof(uint16) - 1])
+
+#define BrinPageFlags(page)		\
+	(((BrinSpecialSpace *)		\
+	  PageGetSpecialPointer(page))->vector[MAXALIGN(1) / sizeof(uint16) - 2])
+
+/* special space on all BRIN pages stores a "type" identifier */
+#define		BRIN_PAGETYPE_META			0xF091
+#define		BRIN_PAGETYPE_REVMAP		0xF092
+#define		BRIN_PAGETYPE_REGULAR		0xF093
+
+#define BRIN_IS_META_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_META)
+#define BRIN_IS_REVMAP_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_REVMAP)
+#define BRIN_IS_REGULAR_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_REGULAR)
+
+/* flags for BrinSpecialSpace */
+#define		BRIN_EVACUATE_PAGE			(1 << 0)
+
+
+/* Metapage definitions */
+typedef struct BrinMetaPageData
+{
+	uint32		brinMagic;
+	uint32		brinVersion;
+	BlockNumber pagesPerRange;
+	BlockNumber lastRevmapPage;
+} BrinMetaPageData;
+
+#define BRIN_CURRENT_VERSION		1
+#define BRIN_META_MAGIC			0xA8109CFA
+
+#define BRIN_METAPAGE_BLKNO		0
+
+/* Definitions for revmap pages */
+typedef struct RevmapContents
+{
+	/*
+	 * This array will fill all available space on the page.  It should be
+	 * declared [FLEXIBLE_ARRAY_MEMBER], but for some reason you can't do that
+	 * in an otherwise-empty struct.
+	 */
+	ItemPointerData rm_tids[1];
+} RevmapContents;
+
+#define REVMAP_CONTENT_SIZE \
+	(BLCKSZ - MAXALIGN(SizeOfPageHeaderData) - \
+	 offsetof(RevmapContents, rm_tids) - \
+	 MAXALIGN(sizeof(BrinSpecialSpace)))
+/* max num of items in the array */
+#define REVMAP_PAGE_MAXITEMS \
+	(REVMAP_CONTENT_SIZE / sizeof(ItemPointerData))
+
+#endif							/* BRIN_PAGE_H */