MDEV-29299 SELECT from table with vcol index reports warning

As of now innodb does not store trx_id for each record in secondary index.
The idea behind is following: let us store only per-page max_trx_id, and
delete-mark the records when they are deleted/updated.

If the read starts, it rememders the lowest id of currently active
transaction. Innodb refers to it as trx->read_view->m_up_limit_id.
See also ReadView::open.

When the page is fetched, its max_trx_id is compared to m_up_limit_id.
If the value is lower, and the secondary index record is not delete-marked,
then this page is just safe to read as is. Else, a clustered index could be
needed ato access. See page_get_max_trx_id call in row_search_mvcc, and the
corresponding switch (row_search_idx_cond_check(...)) below.

Virtual columns are required to be updated in case if the record was
delete-marked. The motivation behind it is documented in
Row_sel_get_clust_rec_for_mysql::operator() near
row_sel_sec_rec_is_for_clust_rec call.

This was basically a description why virtual column computation can
normally happen during SELECT, and, generally, a vcol index access.

Sometimes stats tables are updated by innodb. This starts a new
transaction, and it can happen that it didn't finish to the moment of
SELECT execution, forcing virtual columns recomputation. If the result was
a something that normally outputs a warning, like division by zero, then
it could be outputted in a racy manner.

The solution is to suppress the warnings when a column is computed
for the described purpose.
ignore_wrnings argument is added innobase_get_computed_value.
Currently, it is only true for a call from
row_sel_sec_rec_is_for_clust_rec.

mysql-test/suite/gcol/r/innodb_virtual_index.result

@@ -1,3 +1,4 @@
+SET default_storage_engine= innodb;
 SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
 SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
 #
@@ -310,3 +311,33 @@ ALTER TABLE t1 ADD KEY (b), ALGORITHM=INPLACE;
 # Cleanup
 DROP TABLE t1;
 # End of 10.2 tests
+#
+# MDEV-29299 SELECT from table with vcol index reports warning
+#
+CREATE TABLE t(fld1 INT NOT NULL,
+fld2 INT AS (100/fld1) VIRTUAL,
+KEY(fld1), KEY(fld2));
+CREATE TABLE t_odd(id int);
+INSERT INTO t(fld1) VALUES(1), (2);
+connect stop_purge,localhost,root;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+INSERT INTO t_odd VALUES(10000);
+connection default;
+UPDATE IGNORE t SET fld1= 3 WHERE fld1= 2;
+UPDATE IGNORE t SET fld1= 4 WHERE fld1= 3;
+UPDATE IGNORE t SET fld1= 0 WHERE fld1= 4;
+Warnings:
+Warning	1365	Division by 0
+SELECT fld2 FROM t FORCE INDEX(fld2);
+fld2
+NULL
+100
+SELECT fld2 FROM t FORCE INDEX(fld1);
+fld2
+100
+NULL
+Warnings:
+Warning	1365	Division by 0
+disconnect stop_purge;
+DROP TABLE t, t_odd;
+# End of 10.3 tests

mysql-test/suite/gcol/t/innodb_virtual_index.test

@@ -1,6 +1,8 @@
 --source include/have_innodb.inc
 --source include/have_sequence.inc
 
+SET default_storage_engine= innodb;
+
 # Ensure that the history list length will actually be decremented by purge.
 SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
 SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;
@@ -334,3 +336,30 @@ DROP TABLE t1;
 
 --echo # End of 10.2 tests
 
+--echo #
+--echo # MDEV-29299 SELECT from table with vcol index reports warning
+--echo #
+
+CREATE TABLE t(fld1 INT NOT NULL,
+               fld2 INT AS (100/fld1) VIRTUAL,
+               KEY(fld1), KEY(fld2));
+CREATE TABLE t_odd(id int);
+INSERT INTO t(fld1) VALUES(1), (2);
+
+--connect stop_purge,localhost,root
+# This prevents purge for records in t
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+INSERT INTO t_odd VALUES(10000);
+
+--connection default
+UPDATE IGNORE t SET fld1= 3 WHERE fld1= 2;
+UPDATE IGNORE t SET fld1= 4 WHERE fld1= 3;
+UPDATE IGNORE t SET fld1= 0 WHERE fld1= 4;
+SELECT fld2 FROM t FORCE INDEX(fld2);
+SELECT fld2 FROM t FORCE INDEX(fld1);
+
+--disconnect stop_purge
+DROP TABLE t, t_odd;
+
+
+--echo # End of 10.3 tests

sql/sql_class.h

@@ -1856,6 +1856,21 @@ class MDL_deadlock_and_lock_abort_error_handler: public Internal_error_handler
 };
 
 
+struct Suppress_warnings_error_handler : public Internal_error_handler
+{
+  bool handle_condition(THD *thd,
+                        uint sql_errno,
+                        const char *sqlstate,
+                        Sql_condition::enum_warning_level *level,
+                        const char *msg,
+                        Sql_condition **cond_hdl)
+  {
+    return *level == Sql_condition::WARN_LEVEL_WARN;
+  }
+};
+
+
+
 /**
   Tables that were locked with LOCK TABLES statement.
 

sql/table.cc

@@ -8155,12 +8155,22 @@ int TABLE::update_virtual_fields(handler *h, enum_vcol_update_mode update_mode)
   DBUG_RETURN(in_use->is_error());
 }
 
-int TABLE::update_virtual_field(Field *vf)
+/*
+  Calculate the virtual field value for a specified field.
+  @param vf                     A field to calculate
+  @param ignore_warnings        Ignore calculation warnings. This usually
+                                means that a calculation is internal and is
+                                not expected to fail.
+*/
+int TABLE::update_virtual_field(Field *vf, bool ignore_warnings)
 {
   DBUG_ENTER("TABLE::update_virtual_field");
   Query_arena backup_arena;
   Counting_error_handler count_errors;
+  Suppress_warnings_error_handler warning_handler;
   in_use->push_internal_handler(&count_errors);
+  if (ignore_warnings)
+    in_use->push_internal_handler(&warning_handler);
   /*
     TODO: this may impose memory leak until table flush.
           See comment in
@@ -8172,6 +8182,8 @@ int TABLE::update_virtual_field(Field *vf)
   vf->vcol_info->expr->save_in_field(vf, 0);
   in_use->restore_active_arena(expr_arena, &backup_arena);
   in_use->pop_internal_handler();
+  if (ignore_warnings)
+    in_use->pop_internal_handler();
   DBUG_RETURN(count_errors.errors);
 }
 

sql/table.h

@@ -1610,7 +1610,7 @@ struct TABLE
 
   uint actual_n_key_parts(KEY *keyinfo);
   ulong actual_key_flags(KEY *keyinfo);
-  int update_virtual_field(Field *vf);
+  int update_virtual_field(Field *vf, bool ignore_warnings);
   int update_virtual_fields(handler *h, enum_vcol_update_mode update_mode);
   int update_default_fields(bool ignore_errors);
   void evaluate_update_default_function();

storage/innobase/handler/ha_innodb.cc

@@ -21138,7 +21138,8 @@ innobase_get_computed_value(
 	TABLE*			mysql_table,
 	byte*			mysql_rec,
 	const dict_table_t*	old_table,
-	const upd_t*		update)
+	const upd_t*		update,
+	bool			ignore_warnings)
 {
 	byte		rec_buf2[REC_VERSION_56_MAX_INDEX_COL_LEN];
 	byte*		buf;
@@ -21236,7 +21237,9 @@ innobase_get_computed_value(
 
 	MY_BITMAP *old_write_set = dbug_tmp_use_all_columns(mysql_table, &mysql_table->write_set);
 	MY_BITMAP *old_read_set = dbug_tmp_use_all_columns(mysql_table, &mysql_table->read_set);
-	ret = mysql_table->update_virtual_field(mysql_table->field[col->m_col.ind]);
+	ret = mysql_table->update_virtual_field(
+		mysql_table->field[col->m_col.ind],
+		ignore_warnings);
 	dbug_tmp_restore_column_map(&mysql_table->read_set, old_read_set);
 	dbug_tmp_restore_column_map(&mysql_table->write_set, old_write_set);
 

storage/innobase/include/row0mysql.h

@@ -916,7 +916,9 @@ void innobase_report_computed_value_failed(dtuple_t *row);
 @param[in]	old_table	during ALTER TABLE, this is the old table
 				or NULL.
 @param[in]	update	update vector for the parent row
-@param[in]	foreign		foreign key information
+@param[in]	ignore_warnings	ignore warnings during calculation. Usually
+				means that a calculation is internal and
+				should have no side effects.
 @return the field filled with computed value */
 dfield_t*
 innobase_get_computed_value(
@@ -929,8 +931,9 @@ innobase_get_computed_value(
 	THD*			thd,
 	TABLE*			mysql_table,
 	byte*			mysql_rec,
-	const dict_table_t*	old_table,
-	const upd_t*		update);
+	const dict_table_t*	old_table=NULL,
+	const upd_t*		update=NULL,
+	bool			ignore_warnings=false);
 
 /** Get the computed value by supplying the base column values.
 @param[in,out]	table		the table whose virtual column

storage/innobase/row/row0sel.cc

@@ -329,7 +329,8 @@ row_sel_sec_rec_is_for_clust_rec(
 					&heap, NULL, NULL,
 					thr_get_trx(thr)->mysql_thd,
 					thr->prebuilt->m_mysql_table,
-					record, NULL, NULL);
+					record, NULL, NULL,
+					true);
 
 			if (vfield == NULL) {
 				innobase_report_computed_value_failed(row);

storage/mroonga/mrn_mysql_compat.h

@@ -481,7 +481,7 @@
 #ifdef MRN_MARIADB_P
 #  if (MYSQL_VERSION_ID >= 100203)
 #    define MRN_GENERATED_COLUMNS_UPDATE_VIRTUAL_FIELD(table, field) \
-       (table->update_virtual_field(field))
+       (table->update_virtual_field(field,false))
 #  else
 #    define MRN_GENERATED_COLUMNS_UPDATE_VIRTUAL_FIELD(table, field) \
        (field->vcol_info->expr_item->save_in_field(field, 0))

storage/myisam/ha_myisam.cc

@@ -681,7 +681,7 @@ static int compute_vcols(MI_INFO *info, uchar *record, int keynum)
   {
     Field *f= table->field[kp->fieldnr - 1];
     if (f->vcol_info)
-      table->update_virtual_field(f);
+      table->update_virtual_field(f, false);
   }
   return 0;
 }