/** * Generates a cast for a row type. * * @param rexBuilder RexBuilder to use for constructing casts * @param lhsRowType target row type * @param rhsExps expressions to be cast * @return cast expressions */ public static RexNode[] generateCastExpressions( RexBuilder rexBuilder, RelDataType lhsRowType, RexNode[] rhsExps) { RelDataTypeField[] lhsFields = lhsRowType.getFields(); final int fieldCount = lhsFields.length; RexNode[] castExps = new RexNode[fieldCount]; assert fieldCount == rhsExps.length; for (int i = 0; i < fieldCount; ++i) { RelDataTypeField lhsField = lhsFields[i]; RelDataType lhsType = lhsField.getType(); RelDataType rhsType = rhsExps[i].getType(); if (lhsType.equals(rhsType)) { castExps[i] = rhsExps[i]; } else { castExps[i] = rexBuilder.makeCast(lhsType, rhsExps[i]); } } return castExps; }
// override RexShuttle public RexNode visitCall(final RexCall call) { int i = reducibleExps.indexOf(call); if (i == -1) { return super.visitCall(call); } RexNode replacement = reducedValues.get(i); if (addCasts.get(i) && (replacement.getType() != call.getType())) { // Handle change from nullable to NOT NULL by claiming // that the result is still nullable, even though // we know it isn't. // // Also, we cannot reduce CAST('abc' AS VARCHAR(4)) to 'abc'. // If we make 'abc' of type VARCHAR(4), we may later encounter // the same expression in a ProjectRel's digest where it has // type VARCHAR(3), and that's wrong. replacement = rexBuilder.makeCast(call.getType(), replacement); } return replacement; }