[jira] [Assigned] (IMPALA-7754) Expressions sometimes not re-analyzed after rewrite

["Paul Rogers (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-7754?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Paul Rogers reassigned IMPALA-7754:
-----------------------------------

    Assignee:     (was: Paul Rogers)

> Expressions sometimes not re-analyzed after rewrite
> ---------------------------------------------------
>
>                 Key: IMPALA-7754
>                 URL: https://issues.apache.org/jira/browse/IMPALA-7754
>             Project: IMPALA
>          Issue Type: Bug
>          Components: Frontend
>    Affects Versions: Impala 3.0
>            Reporter: Paul Rogers
>            Priority: Major
>
> The analyzer has a chain of rules which fire in order without (as noted above) repeats. The result of rule A (rewriting conditional functions) is fed into rule B (simplify CASE). Each rule requires that analysis be done so that attributes of expressions can be picked out.
> As it turns out, in the current code, this is rather ad-hoc. The {{SimplifyConditionalsRule}} re-analyzes its result as part of the fix for IMPALA-5125, but others do not, leading to optimizations not working. In particular, in a chain of rewrites for {{IS DISTINCT FROM}}, certain rules didn't fire because previous rules left new expressions in an un-analyzed state. This is a bug.
> The fix is to analyze the result any time a rule fires, before passing the result to the next rule.
> {code:java}
>   private Expr applyRuleBottomUp(Expr expr, ExprRewriteRule rule, Analyzer analyzer)
>       throws AnalysisException {
>     ...
>     Expr rewrittenExpr = rule.apply(expr, analyzer);
>     if (rewrittenExpr != expr) {
>       ++numChanges_;
>       rewrittenExpr.analyze(analyzer); // Add me!
>     }}
>     return rewrittenExpr;
>   }
> {code}
> There are several places that the above logic appears: make the change in all of them.
> Then, in rules that simply refused to run if an expression is to analyzed:
> {code:java}
> public class SimplifyDistinctFromRule implements ExprRewriteRule {
>   public Expr apply(Expr expr, Analyzer analyzer) {
>     if (!expr.isAnalyzed()) return expr;
> {code}
> Replace this with an assertion that analysis must have been done:
> {code:java}
> public class SimplifyDistinctFromRule implements ExprRewriteRule {
>   public Expr apply(Expr expr, Analyzer analyzer) {
>     assert expr.isAnalyzed();
> {code}
> To be safe, the assertion fires only in "debug" mode, not in production.



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