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diff --git a/src/include/access/brin_tuple.h b/src/include/access/brin_tuple.h
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+/*
+ * brin_tuple.h
+ *		Declarations for dealing with BRIN-specific tuples.
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/include/access/brin_tuple.h
+ */
+#ifndef BRIN_TUPLE_H
+#define BRIN_TUPLE_H
+
+#include "access/brin_internal.h"
+#include "access/tupdesc.h"
+
+
+/*
+ * A BRIN index stores one index tuple per page range.  Each index tuple
+ * has one BrinValues struct for each indexed column; in turn, each BrinValues
+ * has (besides the null flags) an array of Datum whose size is determined by
+ * the opclass.
+ */
+typedef struct BrinValues
+{
+	AttrNumber	bv_attno;		/* index attribute number */
+	bool		bv_hasnulls;	/* are there any nulls in the page range? */
+	bool		bv_allnulls;	/* are all values nulls in the page range? */
+	Datum	   *bv_values;		/* current accumulated values */
+} BrinValues;
+
+/*
+ * This struct is used to represent an in-memory index tuple.  The values can
+ * only be meaningfully decoded with an appropriate BrinDesc.
+ */
+typedef struct BrinMemTuple
+{
+	bool		bt_placeholder; /* this is a placeholder tuple */
+	BlockNumber bt_blkno;		/* heap blkno that the tuple is for */
+	MemoryContext bt_context;	/* memcxt holding the bt_columns values */
+	/* output arrays for brin_deform_tuple: */
+	Datum	   *bt_values;		/* values array */
+	bool	   *bt_allnulls;	/* allnulls array */
+	bool	   *bt_hasnulls;	/* hasnulls array */
+	/* not an output array, but must be last */
+	BrinValues	bt_columns[FLEXIBLE_ARRAY_MEMBER];
+} BrinMemTuple;
+
+/*
+ * An on-disk BRIN tuple.  This is possibly followed by a nulls bitmask, with
+ * room for 2 null bits (two bits for each indexed column); an opclass-defined
+ * number of Datum values for each column follow.
+ */
+typedef struct BrinTuple
+{
+	/* heap block number that the tuple is for */
+	BlockNumber bt_blkno;
+
+	/* ---------------
+	 * bt_info is laid out in the following fashion:
+	 *
+	 * 7th (high) bit: has nulls
+	 * 6th bit: is placeholder tuple
+	 * 5th bit: unused
+	 * 4-0 bit: offset of data
+	 * ---------------
+	 */
+	uint8		bt_info;
+} BrinTuple;
+
+#define SizeOfBrinTuple (offsetof(BrinTuple, bt_info) + sizeof(uint8))
+
+/*
+ * bt_info manipulation macros
+ */
+#define BRIN_OFFSET_MASK		0x1F
+/* bit 0x20 is not used at present */
+#define BRIN_PLACEHOLDER_MASK	0x40
+#define BRIN_NULLS_MASK			0x80
+
+#define BrinTupleDataOffset(tup)	((Size) (((BrinTuple *) (tup))->bt_info & BRIN_OFFSET_MASK))
+#define BrinTupleHasNulls(tup)	(((((BrinTuple *) (tup))->bt_info & BRIN_NULLS_MASK)) != 0)
+#define BrinTupleIsPlaceholder(tup) (((((BrinTuple *) (tup))->bt_info & BRIN_PLACEHOLDER_MASK)) != 0)
+
+
+extern BrinTuple *brin_form_tuple(BrinDesc *brdesc, BlockNumber blkno,
+								  BrinMemTuple *tuple, Size *size);
+extern BrinTuple *brin_form_placeholder_tuple(BrinDesc *brdesc,
+											  BlockNumber blkno, Size *size);
+extern void brin_free_tuple(BrinTuple *tuple);
+extern BrinTuple *brin_copy_tuple(BrinTuple *tuple, Size len,
+								  BrinTuple *dest, Size *destsz);
+extern bool brin_tuples_equal(const BrinTuple *a, Size alen,
+							  const BrinTuple *b, Size blen);
+
+extern BrinMemTuple *brin_new_memtuple(BrinDesc *brdesc);
+extern BrinMemTuple *brin_memtuple_initialize(BrinMemTuple *dtuple,
+											  BrinDesc *brdesc);
+extern BrinMemTuple *brin_deform_tuple(BrinDesc *brdesc,
+									   BrinTuple *tuple, BrinMemTuple *dMemtuple);
+
+#endif							/* BRIN_TUPLE_H */