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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]# Re: Testing expression (RexNode) transformations

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Looks awesome! Thanks Julian and Zoltan! -- Michael Mior mmior@xxxxxxxxxx Le mar. 29 mai 2018 à 15:36, Julian Hyde <jhyde@xxxxxxxxxx> a écrit : > With Zoltan’s help, I just committed [1] a nice change to RexSimplify, > adding a “paranoid” flag. If you set paranoid = true, then RexSimplify will > simplify expressions but it will also try to prove that the transformation > is wrong. It does that by assigning sample values to variables and checking > that the simplified expression produces the same result as the original > expression. > > Consider the expression > > (not a) and (b > 5) and (not true) > > This simplifies to “false”, because of the trailing “not true”. “a” is > boolean, so we use sample values {unknown, false, true}; “b” is an integer, > so we use values {null, 0, 1, 1,000,000}. For the 15 (3 x 5) combinations > of assignments to variables (a, b), we evaluate the original expression and > the simplified expression, and make sure they give the same result. If the > result is different, we have proved that the simplification is invalid. I > already found one bug [2] this way. > > I added RexInterpreter (which evaluates RexNode expressions by > interpreting, rather than by generating Java as RexExecutor does) because I > didn’t want to increase coupling. > > One area this could be improved is to add more values based on the > expression. Because the integer literal 5 is present, we ought to check > values {4, 5, 6} in addition to the default values {null, -1, 0, 1, > 1,000,000}. > > It’s really important that our transformation rules can be trusted, so > please use this functionality as much as you can in tests. If you your > transformation does not use RexSimplify, you can use RexAnalyzer directly. > Also, add more tests for rex transformations; each test gives RexSimplifier > a lot of opportunities to find faults. > > Julian > > [1] https://issues.apache.org/jira/browse/CALCITE-2314 < > https://issues.apache.org/jira/browse/CALCITE-2314> > > [2] https://issues.apache.org/jira/browse/CALCITE-2332 < > https://issues.apache.org/jira/browse/CALCITE-2332>

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