MDEV-19385: Inconsistent definition of dtuple_get_nth_v_field()

The accessor dtuple_get_nth_v_field() was defined differently between
debug and release builds in MySQL 5.7.8 in
mysql/mysql-server@c47e175
and a debug assertion to document or enforce the questionable assumption
tuple->v_fields == &tuple->fields[tuple->n_fields] was missing.

This was apparently no problem until MDEV-11369 introduced instant
ADD COLUMN to MariaDB Server 10.3. With that work present, in one
test case, trx_undo_report_insert_virtual() could in release builds
fetch the wrong value for a virtual column.

We replace many of the dtuple_t accessors with const-preserving
inline functions, and fix missing or misleadingly applied const
qualifiers accordingly.

Author: dr-m

storage/innobase/data/data0data.cc

@@ -37,7 +37,7 @@ Created 5/30/1994 Heikki Tuuri
 /** Dummy variable to catch access to uninitialized fields.  In the
 debug version, dtuple_create() will make all fields of dtuple_t point
 to data_error. */
-byte	data_error;
+ut_d(byte data_error);
 #endif /* UNIV_DEBUG */
 
 /** Compare two data tuples.
@@ -416,7 +416,7 @@ dfield_print_also_hex(
 			break;
 		}
 
-		data = static_cast<byte*>(dfield_get_data(dfield));
+		data = static_cast<const byte*>(dfield_get_data(dfield));
 		/* fall through */
 
 	case DATA_BINARY:

storage/innobase/fts/fts0fts.cc

@@ -3366,12 +3366,11 @@ fts_fetch_doc_from_tuple(
                const dict_field_t*     ifield;
                const dict_col_t*       col;
                ulint                   pos;
-               dfield_t*               field;
 
                ifield = dict_index_get_nth_field(index, i);
                col = dict_field_get_col(ifield);
                pos = dict_col_get_no(col);
-               field = dtuple_get_nth_field(tuple, pos);
+		const dfield_t* field = dtuple_get_nth_field(tuple, pos);
 
                if (!get_doc->index_cache->charset) {
                        get_doc->index_cache->charset = fts_get_charset(

storage/innobase/gis/gis0geo.cc

@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2013, 2015, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2019, MariaDB Corporation.
 
 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
@@ -68,9 +69,9 @@ static
 int
 rtree_add_point_to_mbr(
 /*===================*/
-	uchar**	wkb,		/*!< in: pointer to wkb,
+	const uchar**	wkb,		/*!< in: pointer to wkb,
 				where point is stored */
-	uchar*	end,		/*!< in: end of wkb. */
+	const uchar*	end,		/*!< in: end of wkb. */
 	uint	n_dims,		/*!< in: dimensions. */
 	uchar	byte_order,	/*!< in: byte order. */
 	double*	mbr)		/*!< in/out: mbr, which
@@ -108,9 +109,9 @@ static
 int
 rtree_get_point_mbr(
 /*================*/
-	uchar**	wkb,		/*!< in: pointer to wkb,
+	const uchar**	wkb,		/*!< in: pointer to wkb,
 				where point is stored. */
-	uchar*	end,		/*!< in: end of wkb. */
+	const uchar*	end,		/*!< in: end of wkb. */
 	uint	n_dims,		/*!< in: dimensions. */
 	uchar	byte_order,	/*!< in: byte order. */
 	double*	mbr)		/*!< in/out: mbr,
@@ -127,9 +128,9 @@ static
 int
 rtree_get_linestring_mbr(
 /*=====================*/
-	uchar**	wkb,		/*!< in: pointer to wkb,
+	const uchar**	wkb,		/*!< in: pointer to wkb,
 				where point is stored. */
-	uchar*	end,		/*!< in: end of wkb. */
+	const uchar*	end,		/*!< in: end of wkb. */
 	uint	n_dims,		/*!< in: dimensions. */
 	uchar	byte_order,	/*!< in: byte order. */
 	double*	mbr)		/*!< in/out: mbr,
@@ -158,9 +159,9 @@ static
 int
 rtree_get_polygon_mbr(
 /*==================*/
-	uchar**	wkb,		/*!< in: pointer to wkb,
+	const uchar**	wkb,		/*!< in: pointer to wkb,
 				where point is stored. */
-	uchar*	end,		/*!< in: end of wkb. */
+	const uchar*	end,		/*!< in: end of wkb. */
 	uint	n_dims,		/*!< in: dimensions. */
 	uchar	byte_order,	/*!< in: byte order. */
 	double*	mbr)		/*!< in/out: mbr,
@@ -195,9 +196,9 @@ static
 int
 rtree_get_geometry_mbr(
 /*===================*/
-	uchar**	wkb,		/*!< in: pointer to wkb,
+	const uchar**	wkb,		/*!< in: pointer to wkb,
 				where point is stored. */
-	uchar*	end,		/*!< in: end of wkb. */
+	const uchar*	end,		/*!< in: end of wkb. */
 	uint	n_dims,		/*!< in: dimensions. */
 	double*	mbr,		/*!< in/out: mbr. */
 	int	top)		/*!< in: if it is the top,
@@ -297,7 +298,7 @@ stored in "well-known binary representation" (wkb) format.
 int
 rtree_mbr_from_wkb(
 /*===============*/
-	uchar*	wkb,		/*!< in: wkb */
+	const uchar*	wkb,		/*!< in: wkb */
 	uint	size,		/*!< in: size of wkb. */
 	uint	n_dims,		/*!< in: dimensions. */
 	double*	mbr)		/*!< in/out: mbr, which must

storage/innobase/gis/gis0rtree.cc

@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2019, MariaDB Corporation.
 
 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
@@ -64,7 +65,7 @@ rtr_page_split_initialize_nodes(
 	page_t*			page;
 	ulint			n_uniq;
 	ulint			len;
-	byte*			source_cur;
+	const byte*		source_cur;
 
 	block = btr_cur_get_block(cursor);
 	page = buf_block_get_frame(block);
@@ -104,7 +105,7 @@ rtr_page_split_initialize_nodes(
 	}
 
 	/* Put the insert key to node list */
-	source_cur = static_cast<byte*>(dfield_get_data(
+	source_cur = static_cast<const byte*>(dfield_get_data(
 		dtuple_get_nth_field(tuple, 0)));
 	cur->coords = reserve_coords(buf_pos, SPDIMS);
 	rec = (byte*) mem_heap_alloc(
@@ -1874,11 +1875,11 @@ rtr_estimate_n_rows_in_range(
 	ulint		dtuple_f_len MY_ATTRIBUTE((unused));
 	rtr_mbr_t	range_mbr;
 	double		range_area;
-	byte*		range_mbr_ptr;
 
 	dtuple_field = dtuple_get_nth_field(tuple, 0);
 	dtuple_f_len = dfield_get_len(dtuple_field);
-	range_mbr_ptr = reinterpret_cast<byte*>(dfield_get_data(dtuple_field));
+	const byte* range_mbr_ptr = static_cast<const byte*>(
+		dfield_get_data(dtuple_field));
 
 	ut_ad(dtuple_f_len >= DATA_MBR_LEN);
 	rtr_read_mbr(range_mbr_ptr, &range_mbr);

storage/innobase/gis/gis0sea.cc

@@ -1631,15 +1631,13 @@ rtr_get_mbr_from_tuple(
 {
 	const dfield_t* dtuple_field;
         ulint           dtuple_f_len;
-	byte*		data;
 
 	dtuple_field = dtuple_get_nth_field(dtuple, 0);
 	dtuple_f_len = dfield_get_len(dtuple_field);
 	ut_a(dtuple_f_len >= 4 * sizeof(double));
 
-	data = static_cast<byte*>(dfield_get_data(dtuple_field));
-
-	rtr_read_mbr(data, mbr);
+	rtr_read_mbr(static_cast<const byte*>(dfield_get_data(dtuple_field)),
+		     mbr);
 }
 
 /****************************************************************//**

storage/innobase/handler/ha_innodb.cc

@@ -21784,7 +21784,7 @@ void innobase_free_row_for_vcol(VCOL_STORAGE *storage)
 to store the value in passed in "my_rec" */
 dfield_t*
 innobase_get_computed_value(
-	const dtuple_t*		row,
+	dtuple_t*		row,
 	const dict_v_col_t*	col,
 	const dict_index_t*	index,
 	mem_heap_t**		local_heap,