Paul Rogers created IMPALA-7754:
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Summary: 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
Assignee: Paul Rogers
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.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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