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MDEV-34724: Skipping a row operation from a trigger

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Implementation of this task adds ability to raise the signal with
SQLSTATE '02TRG' from a BEFORE INSERT/UPDATE/DELETE trigger and handles
this signal as an indicator meaning 'to throw away the current row'
on processing the INSERT/UPDATE/DELETE statement. The signal with
SQLSTATE '02TRG' has special meaning only in case it is raised inside
BEFORE triggers, for AFTER trigger's this value of SQLSTATE isn't treated
in any special way. In according with SQL standard, the SQLSTATE class '02'
means NO DATA and sql_errno for this class is set to value
ER_SIGNAL_NOT_FOUND by current implementation of MariaDB server.
Implementation of this task assigns the value ER_SIGNAL_SKIP_ROW_FROM_TRIGGER
to sql_errno in Diagnostics_area in case the signal is raised from a trigger
and SQLSTATE has value '02TRG'.

To catch signal with SQLTSATE '02TRG' and handle it in special way, the methods
 Table_triggers_list::process_triggers
 select_insert::store_values
 select_create::store_values
 Rows_log_event::process_triggers
and the overloaded function
 fill_record_n_invoke_before_triggers
were extended with extra out parameter for returning the flag whether
to skip the current values being processed by INSERT/UPDATE/DELETE
statement. This extra parameter is passed as nullptr in case of AFTER trigger
and BEFORE trigger this parameter points to a variable to store a marker
whether to skip the current record or store it by calling write_record().
This commit is contained in:
Dmitry Shulga
2025-01-27 16:29:25 +07:00
parent fcf7211136
commit 4c956fa15b
17 changed files with 1097 additions and 64 deletions
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49
sql/sql_base.cc
View File

@@ -9154,6 +9154,32 @@ static bool not_null_fields_have_null_values(TABLE *table)
return false;
}
/**
The auxiliary function to determine whether a row should be skipped
or handled after invocation of triggers.
@return true in case either there is no BEFORE INSERT triggers or
the statement SIGNAL SQLSTATE '02TRG' wasn't executed by
BEFORE INSERT triggers, else return false meaning that the row
mustn't be processed by the INSERT statement.
*/
static inline bool no_need_to_skip_a_row(bool *skip_row_indicator)
{
/*
A row currently being processed mustn't be skipped in case the parameter
skip_row_indicator passed into fill_record_n_invoke_before_triggers()
is not null (that is true for BEFORE INSERT triggers) and a value stored by
this pointer has the value false, meaning that no SIGNAL statement with
the SQLSTATE = '02TRG' was raised on processing triggers.
*/
return
!skip_row_indicator ||
!*skip_row_indicator;
}
/**
Fill fields in list with values from the list of items and invoke
before triggers.
@@ -9164,6 +9190,9 @@ static bool not_null_fields_have_null_values(TABLE *table)
@param values values to fill with
@param ignore_errors TRUE if we should ignore errors
@param event event type for triggers to be invoked
@param [out] skip_row_indicator the flag whose value tells whether to skip
the current record by INSERT/LOAD statements
or process it
@detail
This function assumes that fields which values will be set and triggers
@@ -9179,7 +9208,8 @@ bool
fill_record_n_invoke_before_triggers(THD *thd, TABLE *table,
List<Item> &fields,
List<Item> &values, bool ignore_errors,
enum trg_event_type event)
enum trg_event_type event,
bool *skip_row_indicator)
{
int result;
Table_triggers_list *triggers= table->triggers;
@@ -9191,7 +9221,7 @@ fill_record_n_invoke_before_triggers(THD *thd, TABLE *table,
{
if (triggers->process_triggers(thd, event, TRG_ACTION_BEFORE,
true, &fields) ||
true, skip_row_indicator, &fields) ||
not_null_fields_have_null_values(table))
{
return TRUE;
@@ -9201,7 +9231,8 @@ fill_record_n_invoke_before_triggers(THD *thd, TABLE *table,
Re-calculate virtual fields to cater for cases when base columns are
updated by the triggers.
*/
if (table->vfield && fields.elements)
if (table->vfield && fields.elements &&
no_need_to_skip_a_row(skip_row_indicator))
{
Item *fld= (Item_field*) fields.head();
Item_field *item_field= fld->field_for_view_update();
@@ -9344,6 +9375,9 @@ err:
@param values values to fill with
@param ignore_errors TRUE if we should ignore errors
@param event event type for triggers to be invoked
@param [out] skip_row_indicator the flag whose value tells whether to skip
the current record by INSERT statement or
process it
@detail
This function assumes that fields which values will be set and triggers
@@ -9358,7 +9392,8 @@ err:
bool
fill_record_n_invoke_before_triggers(THD *thd, TABLE *table, Field **ptr,
List<Item> &values, bool ignore_errors,
enum trg_event_type event)
enum trg_event_type event,
bool *skip_row_indicator)
{
bool result;
Table_triggers_list *triggers= table->triggers;
@@ -9366,13 +9401,15 @@ fill_record_n_invoke_before_triggers(THD *thd, TABLE *table, Field **ptr,
result= fill_record(thd, table, ptr, values, ignore_errors, false, false);
if (!result && triggers && *ptr)
result= triggers->process_triggers(thd, event, TRG_ACTION_BEFORE, TRUE) ||
result= triggers->process_triggers(thd, event, TRG_ACTION_BEFORE, true,
skip_row_indicator) ||
not_null_fields_have_null_values(table);
/*
Re-calculate virtual fields to cater for cases when base columns are
updated by the triggers.
*/
if (!result && triggers && *ptr)
if (!result && triggers && *ptr &&
no_need_to_skip_a_row(skip_row_indicator))
{
DBUG_ASSERT(table == (*ptr)->table);
if (table->vfield)