Daniel Becker created IMPALA-11685:
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Summary: Slot memory sharing between struct and field not working
if the field is also a struct
Key: IMPALA-11685
URL: https://issues.apache.org/jira/browse/IMPALA-11685
Project: IMPALA
Issue Type: Bug
Components: Frontend
Reporter: Daniel Becker
Assignee: Daniel Becker
IMPALA-10838 introduced that if a struct and one of its fields are both present
in the select list, no extra slot is generated in the row for the struct field
but the memory of the struct is reused, i.e. the row size is the same as when
only the struct is queried. It works when the struct field is a primitive type:
{code:java}
explain select id, outer_struct from
functional_orc_def.complextypes_nested_structs;
row-size=64B{code}
{code:java}
explain select id, outer_struct, outer_struct.str from
functional_orc_def.complextypes_nested_structs;
row-size=64B{code}
However, it does not if the child is itself a struct:
{code:java}
explain select id, outer_struct, outer_struct.inner_struct3 from
functional_orc_def.complextypes_nested_structs;
row-size=80B{code}
This is because struct slot descriptors are registered before others so that it
is easier to reuse the slot memory of the struct fields, but struct slot
descriptors among themselves are sorted in the wrong order (see
[https://github.com/apache/impala/blob/c12ac6c27b2df1eae693b44c157d65499f491d21/fe/src/main/java/org/apache/impala/analysis/SelectStmt.java#L340).]
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