/******************************************************
Caching of externally stored column prefixes

(c) 2006 Innobase Oy

Created September 2006 Marko Makela
*******************************************************/

#ifndef row0ext_h
#define row0ext_h

#include "univ.i"
#include "row0types.h"
#include "data0types.h"
#include "mem0mem.h"

/************************************************************************
Creates a cache of column prefixes of externally stored columns. */

row_ext_t*
row_ext_create(
/*===========*/
				/* out,own: column prefix cache */
	ulint		n_ext,	/* in: number of externally stored columns */
	const ulint*	ext,	/* in: col_no's of externally stored columns
				in the InnoDB table object, as reported by
				dict_col_get_no(); NOT relative to the records
				in the clustered index */
	const dtuple_t*	tuple,	/* in: data tuple containing the field
				references of the externally stored columns;
				must be indexed by col_no */
	ulint		zip_size,/* compressed page size in bytes, or 0 */
	mem_heap_t*	heap);	/* in: heap where created */

/************************************************************************
Looks up a column prefix of an externally stored column. */
UNIV_INLINE
const byte*
row_ext_lookup_ith(
/*===============*/
					/* out: column prefix, or NULL if
					the column is not stored externally,
					or pointer to field_ref_zero
					if the BLOB pointer is unset */
	const row_ext_t*	ext,	/* in/out: column prefix cache */
	ulint			i,	/* in: index of ext->ext[] */
	ulint*			len);	/* out: length of prefix, in bytes,
					at most REC_MAX_INDEX_COL_LEN */
/************************************************************************
Looks up a column prefix of an externally stored column. */
UNIV_INLINE
const byte*
row_ext_lookup(
/*===========*/
					/* out: column prefix, or NULL if
					the column is not stored externally,
					or pointer to field_ref_zero
					if the BLOB pointer is unset */
	const row_ext_t*	ext,	/* in: column prefix cache */
	ulint			col,	/* in: column number in the InnoDB
					table object, as reported by
					dict_col_get_no(); NOT relative to the
					records in the clustered index */
	ulint*			len);	/* out: length of prefix, in bytes,
					at most REC_MAX_INDEX_COL_LEN */

/* Prefixes of externally stored columns */
struct row_ext_struct{
	ulint		n_ext;	/* number of externally stored columns */
	const ulint*	ext;	/* col_no's of externally stored columns */
	byte*		buf;	/* backing store of the column prefix cache */
	ulint		len[1];	/* prefix lengths; 0 if not cached */
};

#ifndef UNIV_NONINL
#include "row0ext.ic"
#endif

#endif