[ASTERIXDB-3021][COMP] Emit cross product warning for implicit joins#49
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When a query uses implicit cross join syntax (FROM A, B without a join condition), SimpleUnnestToProductRule rewrites the unnest pipeline into an InnerJoinOperator with a constant TRUE condition but never emits a warning. Explicit JOIN ... ON TRUE already triggers the CROSS_PRODUCT_JOIN warning via JoinUtils. This change closes that gap. - Change warnIfCrossProduct() in JoinUtils from private to public - Call JoinUtils.warnIfCrossProduct() in SimpleUnnestToProductRule after the cross product join is constructed
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Problem
When a SQL++ query uses implicit cross join syntax (e.g.,
FROM customers, orderswithout an explicit join condition),
SimpleUnnestToProductRulerewrites the unnestpipeline into an
InnerJoinOperatorwith a constantTRUEcondition. However, nowarning is emitted to alert the user that a cross product is being performed.
By contrast, an explicit
JOIN ... ON TRUEalready triggers aCROSS_PRODUCT_JOINwarning through
JoinUtils.warnIfCrossProduct(). This inconsistency means users ofthe implicit syntax receive no feedback about potentially expensive cross products,
which can lead to unexpected performance issues or incorrect query results.
Changes
JoinUtils.javawarnIfCrossProduct()fromprivate statictopublic staticso it canbe called from outside the class.
SimpleUnnestToProductRule.javaimportforJoinUtils.JoinUtils.warnIfCrossProduct()immediately after the cross productjoin operator is constructed, consistent with how explicit joins are handled.
Testing
mvn compilepasses on thealgebricks-rewritermodule.mvn testpasses (BUILD SUCCESS) on thealgebricks-rewritermodule.Related