The Volcano planner works in a top-down fashion. It starts by transforming the root and move\n * towards the leafs of the plan. Due to this when transforming a logical join its inputs are\n * still in the logical convention. So, Recursively visit the inputs of the RelNode till\n * BeamIOSourceRel is encountered and propagate the boundedness upwards.\n *\n *
The Boundedness of each child of a RelNode is stored in a list. If any of the children are\n * Unbounded, the RelNode is Unbounded. Else, the RelNode is Bounded.\n *\n * @param relNode the RelNode whose Boundedness has to be determined\n * @return {@code PCollection.isBounded}\n */","sourceCodeStart":205,"sourceCodeEnd":241,"githubUrl":"https://github.com/apache/beam/blob/12126d8942aaf848030c478b4c6a28c6af861c66/sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/rel/BeamJoinRel.java#L205-L241","documentation":"getColumnIndex resolves a join-key operand to an input column index, supporting RexInputRef and RexFieldAccess (recursive). Any other RexNode kind, or an operand whose type cannot be resolved to a column, triggers UnsupportedOperationException with the node's type in the message.","triggerScenarios":"A join predicate operand that is neither a plain column reference nor a struct field access — literals, RexCall expressions, or nested unsupported field-access shapes — passed into getColumnIndex from extractJoinPairOfRexNodes.","commonSituations":"Joining on expressions (concat, casts, arithmetic) or constants inside the ON clause; struct field access patterns deeper than what getColumnIndex recurses into.","solutions":["Ensure both sides of each '=' conjunct are plain column references or struct field accesses","Precompute derived join keys in a subquery/CTE so the join sees bare columns","If extending Beam, add handling for additional RexNode kinds (e.g. RexCall with deterministic functions) in getColumnIndex"],"exampleFix":"// before\nSELECT * FROM a JOIN b ON a.id + 1 = b.id;\n// after\nSELECT * FROM (SELECT id + 1 AS id_next FROM a) a JOIN b ON a.id_next = b.id;","handlingStrategy":"type-guard","validationCode":"// Check join-key operands resolve to plain columns before building the query\nboolean isPlainColumnOrField(String expr) {\n return expr.matches(\"\\\\w+\") || expr.matches(\"\\\\w+(\\\\.\\\\w+)+\"); // no function calls/casts/arithmetic\n}","typeGuard":"static boolean isResolvableJoinKey(RexNode node) {\n return node instanceof RexInputRef\n || (node instanceof RexFieldAccess\n && isResolvableJoinKey(((RexFieldAccess) node).getReferenceExpr()));\n}","tryCatchPattern":"try {\n result = sqlEnv.sqlQuery(q).evaluate();\n} catch (UnsupportedOperationException e) {\n if (e.getMessage().startsWith(\"Cannot get column index from\")) {\n q = projectJoinKeysFirst(q);\n } else throw e;\n}","preventionTips":["Use bare column references as join keys","Compute derived keys in a preceding projection","Recursively validate struct-field join keys match what getColumnIndex supports"],"tags":["sql","join","column-index","beam"],"backgroundTag":"unsupported-operation","analyzedSha":"12126d8942aaf848030c478b4c6a28c6af861c66","analyzedAt":"2026-09-13T01:50:10.254Z","contentChangedAt":"2026-09-13T01:50:10.254Z","schemaVersion":2},"datasetVersion":"2026-09-14T16:17:12.679Z"}