branches/zip: Add row_ext_t for caching prefixes of externally stored columns.

This will be needed for fixing Bug #22496.

REC_MAX_INDEX_COL_LEN: New constant, copied from DICT_MAX_INDEX_COL_LEN.

row_ext_create(), row_ext_lookup(), row_ext_lookup_low(): New functions.

Makefile.am

@@ -70,6 +70,7 @@ EXTRA_DIST = 	include/btr0btr.h include/btr0btr.ic include/btr0cur.h include/btr
 		include/read0read.h include/read0read.ic include/read0types.h \
 		include/rem0cmp.h include/rem0cmp.ic include/rem0rec.h include/rem0rec.ic \
 		include/rem0types.h \
+		include/row0ext.h include/row0ext.ic \
 		include/row0ins.h include/row0ins.ic include/row0mysql.h include/row0mysql.ic \
 		include/row0purge.h include/row0purge.ic include/row0row.h include/row0row.ic \
 		include/row0sel.h include/row0sel.ic include/row0types.h \

include/dict0mem.h

@@ -165,12 +165,7 @@ struct dict_col_struct{
 				is defined on the entire column */
 };
 
-/* DICT_MAX_INDEX_COL_LEN is measured in bytes and is the max index column
-length + 1. Starting from 4.1.6, we set it to < 3 * 256, so that one can
-create a column prefix index on 255 characters of a TEXT field also in the
-UTF-8 charset. In that charset, a character may take at most 3 bytes. */
-
-#define DICT_MAX_INDEX_COL_LEN		768
+#define DICT_MAX_INDEX_COL_LEN		REC_MAX_INDEX_COL_LEN
 
 /* Data structure for a field in an index */
 struct dict_field_struct{

include/rem0types.h

@@ -17,4 +17,10 @@ typedef byte	rec_t;
 #define REC_MAX_HEAP_NO		(2 * 8192 - 1)
 #define REC_MAX_N_OWNED		(16 - 1)
 
+/* REC_MAX_INDEX_COL_LEN is measured in bytes and is the max index column
+length + 1. Starting from 4.1.6, we set it to 3 * 256, so that one can
+create a column prefix index on 255 characters of a TEXT field also in the
+UTF-8 charset. Under MySQL, a UTF-8 character may take at most 3 bytes. */
+#define REC_MAX_INDEX_COL_LEN	768
+
 #endif

include/row0ext.h

+/******************************************************
+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 "mem0mem.h"
+
+/************************************************************************
+Creates a cache of column prefixes of externally stored columns. */
+UNIV_INLINE
+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 */
+	ulint		zip_size,/* compressed page size, or 0 */
+	mem_heap_t*	heap);	/* in: heap where created */
+
+/************************************************************************
+Looks up a column prefix of an externally stored column. */
+UNIV_INLINE
+byte*
+row_ext_lookup(
+/*===========*/
+				/* out: column prefix */
+	row_ext_t*	ext,	/* in/out: column prefix cache */
+	ulint		col,	/* in: column number */
+	const byte*	field,	/* in: locally stored part of the column */
+	ulint		f_len,	/* in: length of field, in bytes */
+	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 */
+	ulint		zip_size;/* compressed page size, or 0 */
+	char*		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

include/row0ext.ic

+/******************************************************
+Caching of externally stored column prefixes
+
+(c) 2006 Innobase Oy
+
+Created September 2006 Marko Makela
+*******************************************************/
+
+#include "rem0types.h"
+
+/************************************************************************
+Looks up and caches a column prefix of an externally stored column. */
+
+byte*
+row_ext_lookup_low(
+/*===============*/
+				/* out: column prefix */
+	row_ext_t*	ext,	/* in/out: column prefix cache */
+	ulint		i,	/* in: index of ext->ext[] */
+	const byte*	field,	/* in: locally stored part of the column */
+	ulint		f_len,	/* in: length of field, in bytes */
+	ulint*		len);	/* out: length of prefix, in bytes,
+				at most REC_MAX_INDEX_COL_LEN */
+
+/************************************************************************
+Creates a cache of column prefixes of externally stored columns. */
+UNIV_INLINE
+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 */
+	ulint		zip_size,/* compressed page size, or 0 */
+	mem_heap_t*	heap)	/* in: heap where created */
+{
+	row_ext_t*	ret = mem_heap_alloc(heap, (sizeof *ret) - 1 + n_ext);
+
+	ret->n_ext = n_ext;
+	ret->ext = ext;
+	ret->zip_size = zip_size;
+	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);
+#endif
+	memset(ret->len, 0, n_ext * sizeof *ret->len);
+
+	return(ret);
+}
+
+/************************************************************************
+Looks up a column prefix of an externally stored column. */
+UNIV_INLINE
+byte*
+row_ext_lookup(
+/*===========*/
+				/* out: column prefix */
+	row_ext_t*	ext,	/* in/out: column prefix cache */
+	ulint		col,	/* in: column number */
+	const byte*	field,	/* in: locally stored part of the column */
+	ulint		f_len,	/* in: length of field, in bytes */
+	ulint*		len)	/* out: length of prefix, in bytes,
+				at most REC_MAX_INDEX_COL_LEN */
+{
+	ulint	i;
+
+	ut_ad(ext);
+	ut_ad(field);
+	ut_ad(len);
+
+	for (i = 0; i < ext->n_ext; i++) {
+		if (col == ext->ext[i]) {
+			/* Return from the cache if found */
+			if (ext->len[i]) {
+				*len = ext->len[i];
+				ut_ad(*len > f_len);
+				return(ext->buf + i * REC_MAX_INDEX_COL_LEN);
+			}
+
+			/* Update the cache */
+			return(row_ext_lookup_low(ext, i, field, f_len, len));
+		}
+	}
+
+	/* The column should always be found. */
+	ut_error;
+	return(NULL);
+}

include/row0types.h

@@ -34,4 +34,6 @@ typedef	struct undo_node_struct undo_node_t;
 
 typedef	struct purge_node_struct purge_node_t;
 
+typedef struct row_ext_struct row_ext_t;
+
 #endif

row/Makefile.am

@@ -19,7 +19,8 @@ include ../include/Makefile.i
 
 noinst_LIBRARIES =	librow.a
 
-librow_a_SOURCES =	row0ins.c row0mysql.c row0purge.c row0row.c row0sel.c\
+librow_a_SOURCES =	row0ext.c\
+			row0ins.c row0mysql.c row0purge.c row0row.c row0sel.c\
 			row0uins.c row0umod.c row0undo.c row0upd.c row0vers.c
 
 EXTRA_PROGRAMS =	

row/row0ext.c

+/******************************************************
+Caching of externally stored column prefixes
+
+(c) 2006 Innobase Oy
+
+Created September 2006 Marko Makela
+*******************************************************/
+
+#include "row0ext.h"
+
+#ifdef UNIV_NONINL
+#include "row0ext.ic"
+#endif
+
+#include "btr0cur.h"
+
+/************************************************************************
+Looks up and caches a column prefix of an externally stored column. */
+
+byte*
+row_ext_lookup_low(
+/*===============*/
+				/* out: column prefix */
+	row_ext_t*	ext,	/* in/out: column prefix cache */
+	ulint		i,	/* in: index of ext->ext[] */
+	const byte*	field,	/* in: locally stored part of the column */
+	ulint		f_len,	/* in: length of field, in bytes */
+	ulint*		len)	/* out: length of prefix, in bytes,
+				at most REC_MAX_INDEX_COL_LEN */
+{
+	byte*	buf	= ext->buf + i * REC_MAX_INDEX_COL_LEN;
+
+	ut_ad(i < ext->n_ext);
+
+	*len = ext->len[i] = btr_copy_externally_stored_field_prefix(
+		buf,
+		REC_MAX_INDEX_COL_LEN, ext->zip_size, field, f_len);
+	return(buf);
+}