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  1. MariaDB Server
  2. MDEV-30099

DELETE .. RETURNING does not always return metadata

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      Description

      In some cases DELETE ... RETURNING which does not delete any rows does not return metadata. In other cases it does. Apparently it is not the expected behavior/

      create table t (a int);
      --enable_metadata
      delete from t returning *;
      delete from t where 0 returning *;
      delete from t where not exists (select * from mysql.user) returning *;
      select * from t where 0;
       
      # Cleanup
      --disable_metadata
      drop table t;
      

      10.3 162c1505

      delete from t returning *;
      Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
      def	test	t	t	a	a	3	11	0	Y	32768	0	63
      a
      delete from t where 0 returning *;
      delete from t where not exists (select * from mysql.user) returning *;
      select * from t where 0;
      Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
      def	test	t	t	a	a	3	11	0	Y	32768	0	63
      a
      

      So, DELETE without a WHERE clause returns metadata, even though the table is empty. But DELETE with an impossible condition does not.
      SELECT however returns metadata with the same impossible conditions.

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            Assignee:
            rucha174 Rucha Deodhar
            Reporter:
            elenst Elena Stepanova
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              Updated:

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