答复: which cube to use when u build many cubes under a model

[仇同心 <qi...@jd.com>]

     Kylin completed a customized Adapter, completed in Calcite SQL parsing, forming a syntax tree (AST), defined by Kylin syntax tree each node query execution rules.Calcite after traversal syntax tree node generated a Kylin describe the Digest of the query model, Kylin will Digest to judge whether there is a match for this Cube.If there is a Cube with the query matching, that is, to choose a minimum Cost of query to query the Cube (KylinCube query Cost calculation is an open interface, can according to the number of dimensions, can be based on the quantity to calculate Cost data)

In CubeInstance.java:

You  can see:
      @Override
    public CapabilityResult isCapable(SQLDigest digest) {
        CapabilityResult result = CubeCapabilityChecker.check(this, digest);
        if (result.capable) {
            result.cost = getCost(digest);
            for (CapabilityInfluence i : result.influences) {
                result.cost *= (i.suggestCostMultiplier() == 0) ? 1.0 : i.suggestCostMultiplier();
            }
        } else {
            result.cost = -1;
        }
        return result;
    }

    private int getCost(SQLDigest digest) {
        int calculatedCost = cost;

        //the number of dimensions is not as accurate as number of row key cols
        calculatedCost += getRowKeyColumnCount() * COST_WEIGHT_DIMENSION + getMeasures().size() * COST_WEIGHT_MEASURE;

        for (LookupDesc lookupDesc : this.getDescriptor().getModel().getLookups()) {
            // more tables, more cost
            if ("inner".equals(lookupDesc.getJoin().getType())) {
                // inner join cost is bigger than left join, as it will filter some records
                calculatedCost += COST_WEIGHT_INNER_JOIN;
            }
        }

        return calculatedCost;
    }

发件人: Mars J [mailto:xujiao.mycafe@gmail.com]
发送时间: 2016年9月13日 15:04
收件人: user@kylin.apache.org
主题: which cube to use when u build many cubes under a model

Hi ,
     I'm every curious about that if I define and build many cubes under one specific model, e.g cube1,cube2,cube3, these cubes may have same dimensions, so if a query invole such a dimension ,which cube kylin will use to respond ?