column_filter_outbound_func_indexes.h

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#ifndef CS_COLUMN_FILTER_OUTBOUND_FUNC_INDEX_H
#define CS_COLUMN_FILTER_OUTBOUND_FUNC_INDEX_H
 
#include "sql/changestreams/misc/column_filters/column_filter.h"
#include "sql/rpl_utility.h"  // table_def
 
namespace cs {
namespace util {
/**
  @class Column_filter_outbound_func_indexes
 
  One use case for filtering relates to hidden generated columns. These type
  of columns are used to support functional indexes and are not meant to be
  replicated nor included in the serialization/deserialization of binlog
  events.  Moreover, since hidden generated columns are always placed at the
  end of the field set, replication would break for cases where replicas have
  extra columns, if they were not excluded from replication:
 
       SOURCE TABLE `t`                REPLICA TABLE `t`
       +----+----+----+------+------+  +----+----+----+-----+------+------+
       | C1 | C2 | C3 | HGC1 | HGC2 |  | C1 | C2 | C3 | EC1 | HGC1 | HGC2 |
       +----+----+----+------+------+  +----+----+----+-----+------+------+
 
  In the above example, the extra column `EC1` in the replica will be paired
  with the hidden generated column `HGC1` of the source, if hidden generated
  columns were to be replicated. With filtering enabled for hidden generated
  columns, applier will observe the columns as follows:
 
       SOURCE TABLE `t`                REPLICA TABLE `t`
       +----+----+----+                +----+----+----+-----+
       | C1 | C2 | C3 |                | C1 | C2 | C3 | EC1 |
       +----+----+----+                +----+----+----+-----+
 
   Outbound states we are encoding something to be transmitted.
 */
class ColumnFilterOutboundFunctionalIndexes : public ColumnFilter {
  bool filter_column(TABLE const *table, size_t column_index) override;
  /**
    @brief Is this filter needed given context passed in the parameters
 
    @param thd the thread objected associated to filter
    @param table the table where the columns are being iterated
    @param tabledef the source table definition if applicable
    @return true if the filter should be used
    @return false if the filter is not needed
  */
 public:
  static bool is_filter_needed(THD const &thd, TABLE *table,
                               table_def const *tabledef);
};
}  // namespace util
}  // namespace cs
#endif  // CS_COLUMN_FILTER_OUTBOUND_FUNC_INDEX_H