[IMPALA-5356] Move Expr's fragment local states from ExprContext to Expr

• Type: Task
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: Impala 2.8.0
• Component/s: Backend
• Target Version: Product Backlog
• Epic Color: ghx-label-2
• Assignee: Michael Ho
• Reporter: Michael Ho
• Created: 24/May/17 01:31
• Updated: 24/May/17 01:35

Description

Currently, Exprs' FRAGMENT_LOCAL states are stored in their FunctionContext which is part of ExprContext. Usually, these states are evaluated during Prepare() phase of ExprContext.

Once https://gerrit.cloudera.org/#/c/5483 is committed, these fragment local states will be initialized as part of the expression evaluators' initialization. Ideally, these states should be initialized once and stashed along with the Expr stored in the fragment states instead of having one copy of it per fragment instance. Note that some of these FRAGMENT_LOCAL states are not exactly cheap to initialize (e.g. LIKE predicate may allocate a RE object with the compiled regexp).

Issue Links

• relates to: IMPALA-4080 Share codegen work between fragment instances