Add dict_col_t::same_format()

dict_col_t::same_format(): Check if two columns have the same
data type and compatible length.

storage/innobase/handler/handler0alter.cc

@@ -205,6 +205,15 @@ inline void dict_table_t::prepare_instant(const dict_table_t& old,
 		DBUG_ASSERT(index.n_fields >= oindex.n_fields);
 		DBUG_ASSERT(index.n_fields > oindex.n_fields
 			    || !not_redundant());
+#ifdef UNIV_DEBUG
+		if (index.n_fields == oindex.n_fields) {
+			ut_ad(!not_redundant());
+			for (unsigned i = index.n_fields; i--; ) {
+				ut_ad(index.fields[i].col->same_format(
+					      *oindex.fields[i].col));
+			}
+		}
+#endif
 set_core_fields:
 		index.n_core_fields = oindex.n_core_fields;
 		index.n_core_null_bytes = oindex.n_core_null_bytes;
@@ -389,6 +398,8 @@ inline void dict_index_t::instant_add_field(const dict_index_t& instant)
 #ifndef DBUG_OFF
 	for (unsigned i = 0; i < n_fields; i++) {
 		DBUG_ASSERT(fields[i].same(instant.fields[i]));
+		DBUG_ASSERT(instant.fields[i].col->same_format(*fields[i]
+							       .col));
 		/* Instant conversion from NULL to NOT NULL is not allowed. */
 		DBUG_ASSERT(!fields[i].col->is_nullable()
 			    || instant.fields[i].col->is_nullable());
@@ -5439,13 +5450,10 @@ static bool innobase_instant_try(
 
 		bool update = old && (!ctx->first_alter_pos
 				      || i < ctx->first_alter_pos - 1);
-		DBUG_ASSERT(!old || !((old->prtype ^ col->prtype)
-				      & ~(DATA_NOT_NULL | DATA_VERSIONED)));
+		DBUG_ASSERT(!old || col->same_format(*old));
 		if (update
 		    && old->prtype == d->type.prtype) {
 			/* The record is already present in SYS_COLUMNS. */
-			DBUG_ASSERT(old->mtype == col->mtype);
-			DBUG_ASSERT(old->len == col->len);
 		} else if (innodb_insert_sys_columns(user_table->id, i,
 						     (*af)->field_name.str,
 						     d->type.mtype,

storage/innobase/include/dict0mem.h

@@ -684,6 +684,20 @@ struct dict_col_t{
 		def_val.len = UNIV_SQL_DEFAULT;
 		def_val.data = NULL;
 	}
+
+	/** Determine if the columns have the same format
+	except for is_nullable() and is_versioned().
+	@param[in]	other	column to compare to
+	@return	whether the columns have the same format */
+	bool same_format(const dict_col_t& other) const
+	{
+		return mtype == other.mtype
+			&& len >= other.len
+			&& mbminlen == other.mbminlen
+			&& mbmaxlen == other.mbmaxlen
+			&& !((prtype ^ other.prtype)
+			     & ~(DATA_NOT_NULL | DATA_VERSIONED));
+	}
 };
 
 /** Index information put in a list of virtual column structure. Index