Fix instant DROP COLUMN of multiple columns

innobase_instant_drop_col(): Remove the parameter for the table name.
The InnoDB data dictionary could be out of sync with the .frm file,
because renaming columns between upper and lower case may not be
reflected by the InnoDB dictionary.

innobase_op_instant_try(): Remember the number of the last stored
column, and support dropping multiple columns at a time.
FIXME: adjust SYS_COLUMNS.POS for the pre-existing (not added)
virtual columns.

storage/innobase/handler/handler0alter.cc

@@ -4329,7 +4329,7 @@ static bool innobase_instant_add_col(
 			"END;\n", FALSE, trx);
 	if (err != DB_SUCCESS) {
 		my_error(ER_INTERNAL_ERROR, MYF(0),
-				"InnoDB: Insert into SYS_COLUMNS failed");
+			 "InnoDB: Insert into SYS_COLUMNS failed");
 		return(true);
 	}
 
@@ -4337,33 +4337,27 @@ static bool innobase_instant_add_col(
 }
 
 /** Delete the column from the sys_columns system table.
-@param[in]	table_id	table id
-@param[in]	pos		position of the column
-@param[in]	field_name	field name
-@param[in]	trx		transaction
+@param[in]	id	table id
+@param[in]	pos	SYS_COLUMNS.POS
+@param[in,out]	trx	data dictionary transaction
 @retval true Failure
-@retval false success. */
-static bool innobase_instant_drop_col(
-	table_id_t	table_id,
-	ulint		pos,
-	const char*	field_name,
-	trx_t*		trx)
+@retval false Success. */
+static bool innobase_instant_drop_col(table_id_t id, ulint pos, trx_t* trx)
 {
 	pars_info_t*	info = pars_info_create();
-	pars_info_add_ull_literal(info, "id", table_id);
+	pars_info_add_ull_literal(info, "id", id);
 	pars_info_add_int4_literal(info, "pos", pos);
-	pars_info_add_str_literal(info, "name", field_name);
 
 	dberr_t err = que_eval_sql(
 			info,
 			"PROCEDURE DELETE_COL () IS\n"
 			"BEGIN\n"
 			"DELETE FROM SYS_COLUMNS WHERE \n"
-			"TABLE_ID = :id AND NAME = :name;\n"
+			"TABLE_ID = :id AND POS = :pos;\n"
 			"END;\n", FALSE, trx);
 	if (err != DB_SUCCESS) {
 		my_error(ER_INTERNAL_ERROR, MYF(0),
-				"InnoDB: DELETE from SYS_COLUMNS failed");
+			 "InnoDB: DELETE from SYS_COLUMNS failed");
 		return true;
 	}
 
@@ -4435,7 +4429,7 @@ innobase_op_instant_try(
 
 	dict_index_t* index = dict_table_get_first_index(user_table);
 	/* The table may have been emptied and may have lost its
-	'instant-add-ness' during this instant ADD COLUMN. */
+	'instantness' during this ALTER TABLE. */
 
 	/* Construct a table row of default values for the stored columns. */
 	dtuple_t* row = dtuple_create(ctx->heap, user_table->n_cols);
@@ -4445,24 +4439,23 @@ innobase_op_instant_try(
 	Field**	uf = table->field;
 	Field** const uf_end = table->field + table->s->fields;
 
-	bool	update_pos = false;
-	for (ulint i = 0; uf < uf_end; uf++) {
+	for (ulint i = 0, next_pos = 0; uf < uf_end; uf++) {
 		if (!(*uf)->stored_in_db()) {
 			continue;
 		}
 
 		if (ctx->col_map[i] == ULINT_UNDEFINED) {
-
-			/* Remove this column entry from sys_column */
-			if (innobase_instant_drop_col(
-				user_table->id, i, (*uf)->field_name.str, trx)) {
+			if (innobase_instant_drop_col(user_table->id, i,
+						      trx)) {
 				return true;
 			}
 
-			update_pos = true;
-		} else if (update_pos) {
+			if (!next_pos) {
+				next_pos = i + 1;
+			}
+		} else if (next_pos) {
 			if (innobase_instant_update_pos(
-				user_table->id, i, i - 1, trx)) {
+				user_table->id, i, next_pos++ - 1, trx)) {
 				return true;
 			}
 		}