Paul Rogers created IMPALA-7896:
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Summary: Literals should not need explicit analyze step
Key: IMPALA-7896
URL: https://issues.apache.org/jira/browse/IMPALA-7896
Project: IMPALA
Issue Type: Improvement
Components: Frontend
Affects Versions: Impala 3.0
Reporter: Paul Rogers
Assignee: Paul Rogers
The Impala FE has the concept of a _lteral_ (string, boolean, null, number.)
Originally, literals could only be created as part of the AST. Hence, all
literals are subclasses of {{LiteralExpr}} which are {{ExprNodes}}. The
analysis step is used to set the type of the literal numbers, when not known at
create time. If literals were used only in the AST, this would be fine, they
could be analyzed with an analyzer.
In fact, as the code has evolved, {{LiteralExpr}} nodes are created via the
catalog, which has no analyzer. To fudge the issue, the
{{LiteralExpr.create()}} function does analysis with a null analyzer. This, in
turn, means that the {{analyze()}} code needs to special case a null analyzer.
This, in turn, leads to brittle, error prone code.
Since literals are immutable (except, sadly, for type), it is better that they
start analyzed. Since the only attribute which must be set is the type, and the
type can be known at create time, we have the {{analyze()}} be an optional
no-op, leading to cleaner semantics.
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