~drizzle-trunk/drizzle/development

/*****************************************************************************

Copyright (c) 2006, 2009, Innobase Oy. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free Software

Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT

ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with

this program; if not, write to the Free Software Foundation, Inc., 51 Franklin

St, Fifth Floor, Boston, MA 02110-1301 USA

*****************************************************************************/

/**************************************************//**

@file row/row0ext.c

Caching of externally stored column prefixes

Created September 2006 Marko Makela

*******************************************************/

#include "row0ext.h"

#ifdef UNIV_NONINL

#include "row0ext.ic"

#endif

#include "btr0cur.h"

/********************************************************************//**

Fills the column prefix cache of an externally stored column. */

static

void

row_ext_cache_fill(

/*===============*/

	row_ext_t*	ext,	/*!< in/out: column prefix cache */

	ulint		i,	/*!< in: index of ext->ext[] */

	ulint		zip_size,/*!< compressed page size in bytes, or 0 */

	const dfield_t*	dfield)	/*!< in: data field */

{

	const byte*	field	= dfield_get_data(dfield);

	ulint		f_len	= dfield_get_len(dfield);

	byte*		buf	= ext->buf + i * REC_MAX_INDEX_COL_LEN;

	ut_ad(i < ext->n_ext);

	ut_ad(dfield_is_ext(dfield));

	ut_a(f_len >= BTR_EXTERN_FIELD_REF_SIZE);

	if (UNIV_UNLIKELY(!memcmp(field_ref_zero,

				  field + f_len - BTR_EXTERN_FIELD_REF_SIZE,

				  BTR_EXTERN_FIELD_REF_SIZE))) {

		/* The BLOB pointer is not set: we cannot fetch it */

		ext->len[i] = 0;

	} else {

		/* Fetch at most REC_MAX_INDEX_COL_LEN of the column.

		The column should be non-empty.  However,

		trx_rollback_or_clean_all_recovered() may try to

		access a half-deleted BLOB if the server previously

		crashed during the execution of

		btr_free_externally_stored_field(). */

		ext->len[i] = btr_copy_externally_stored_field_prefix(

			buf, REC_MAX_INDEX_COL_LEN, zip_size, field, f_len);

	}

}

/********************************************************************//**

Creates a cache of column prefixes of externally stored columns.

@return	own: column prefix cache */

UNIV_INTERN

row_ext_t*

row_ext_create(

/*===========*/

	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;

				the clustered index record must be

				covered by a lock or a page latch

				to prevent deletion (rollback or purge). */

	ulint		zip_size,/*!< compressed page size in bytes, or 0 */

	mem_heap_t*	heap)	/*!< in: heap where created */

{

	ulint		i;

	row_ext_t*	ret = mem_heap_alloc(heap, (sizeof *ret)

					     + (n_ext - 1) * sizeof ret->len);

	ut_ad(ut_is_2pow(zip_size));

	ut_ad(zip_size <= UNIV_PAGE_SIZE);

	ret->n_ext = n_ext;

	ret->ext = ext;

	ret->buf = mem_heap_alloc(heap, n_ext * REC_MAX_INDEX_COL_LEN);

#ifdef UNIV_DEBUG

	memset(ret->buf, 0xaa, n_ext * REC_MAX_INDEX_COL_LEN);

	UNIV_MEM_ALLOC(ret->buf, n_ext * REC_MAX_INDEX_COL_LEN);

#endif

	/* Fetch the BLOB prefixes */

	for (i = 0; i < n_ext; i++) {

		const dfield_t*	dfield;

		dfield = dtuple_get_nth_field(tuple, ext[i]);

		row_ext_cache_fill(ret, i, zip_size, dfield);

	}

	return(ret);

}