[GitHub] [shardingsphere] wgy8283335 commented on issue #13010: Add metadata query for volcano planner and related unit test.

[GitBox <gi...@apache.org>]

wgy8283335 commented on issue #13010:
URL: https://github.com/apache/shardingsphere/issues/13010#issuecomment-941819876


   We should implement the interface to provide statistics.
   These method 'getRowCount()', 'isKey(ImmutableBitSet columns)','getKeys()' should be implement firstly.
   ```
   public interface Statistic {
     /** Returns the approximate number of rows in the table. */
     default Double getRowCount() {
       return null;
     }
   
     /** Returns whether the given set of columns is a unique key, or a superset
      * of a unique key, of the table.
      */
     default boolean isKey(ImmutableBitSet columns) {
       return false;
     }
   
     /** Returns a list of unique keys, or null if no key exist. */
     default List<ImmutableBitSet> getKeys() {
       return null;
     }
   
     /** Returns the collection of referential constraints (foreign-keys)
      * for this table. */
     default List<RelReferentialConstraint> getReferentialConstraints() {
       return null;
     }
   
     /** Returns the collections of columns on which this table is sorted. */
     default List<RelCollation> getCollations() {
       return null;
     }
   
     /** Returns the distribution of the data in this table. */
     default RelDistribution getDistribution()  {
       return null;
     }
   }
   ```


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