private boolean canMinMaxDimAnsweredByMetadata()

in src/query-common/src/main/java/org/apache/kylin/query/relnode/OlapContext.java [553:618]
48 lines of code
21 McCabe index (conditional complexity)

    private boolean canMinMaxDimAnsweredByMetadata(OlapRel rel, boolean resetAggWhenMatch) {
        if (!KylinConfig.getInstanceFromEnv().isRouteToMetadataEnabled()) {
            return false;
        }

        if (!(realization instanceof NDataflow) || !(rel instanceof OlapJoinRel || rel instanceof OlapTableScan)) {
            logger.info("Can't route to metadata, the realization is {} and this OlapRel is {}", realization, rel);
            return false;
        }

        /*
         * Find the target pattern as shown below.
         *       (other rel)
         *            |
         *           Agg
         *            |
         *          Project
         *            |
         *   (TableScan or JoinRel)
         */
        List<OlapRel> relStack = new ArrayList<>();
        OlapRel current = this.topNode;
        while (current != rel && current.getInputs().size() == 1 && current.getInput(0) instanceof OlapRel) {
            relStack.add(current);
            current = (OlapRel) current.getInput(0);
        }
        if (current != rel || relStack.size() < 2 || !(relStack.get(relStack.size() - 1) instanceof OlapProjectRel)
                || !(relStack.get(relStack.size() - 2) instanceof OlapAggregateRel)) {
            logger.info("Can't route to query metadata, the rel stack is not matched");
            return false;
        }

        OlapAggregateRel aggregateRel = (OlapAggregateRel) relStack.get(relStack.size() - 2);
        if (aggregateRel.getGroups().size() > 1
                || aggregateRel.getGroups().size() == 1 && !TblColRef.InnerDataTypeEnum.LITERAL.getDataType()
                        .equals(aggregateRel.getGroups().get(0).getDatatype())) {
            logger.info("Cannot route to query metadata, only group by constants are supported.");
            return false;
        }

        if (aggregations.isEmpty() || !aggregations.stream().allMatch(agg -> agg.isMin() || agg.isMax())) {
            logger.info("Cannot route to query metadata, only min/max aggregate functions are supported.");
            return false;
        }

        if (aggregations.stream()
                .anyMatch(agg -> TblColRef.InnerDataTypeEnum.contains(agg.getColRefs().get(0).getDatatype()))) {
            logger.info("Cannot route to query metadata, not support min(expression), such as min(id+1)");
            return false;
        }

        if (!Sets.newHashSet(realization.getAllDimensions()).containsAll(allColumns)) {
            logger.info("Cannot route to query metadata, not all columns queried are treated as dimensions of index.");
            return false;
        }

        if (resetAggWhenMatch) {
            // reset rewriteAggCalls to aggCall, to avoid using measures.
            aggregateRel.getRewriteAggCalls().clear();
            aggregateRel.getRewriteAggCalls().addAll(aggregateRel.getAggCallList());
            logger.info("Use kylin metadata to answer query with realization : {}", realization);
        } else {
            logger.info("OlapContext can be answered by kylin metadata with realization : {}", realization);
        }
        return true;
    }