[IMPALA-7896] Literals should not need explicit analyze step

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: Impala 3.0
• Component/s: Frontend
• Epic Color: ghx-label-3
• Assignee: Paul Rogers
• Reporter: Paul Rogers
• Created: 27/Nov/18 00:52
• Updated: 02/Jan/19 11:23
• Resolved: 29/Dec/18 00:00

Description

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.

Issue Links

• Is contained by: IMPALA-7902 Revise NumericLiteral to avoid analysis, fix multiple issues