chunweilei commented on a change in pull request #1141: [CALCITE-2914] Improve
how LatticeSuggester deduces foreign keys
URL: https://github.com/apache/calcite/pull/1141#discussion_r270787328
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File path:
core/src/main/java/org/apache/calcite/materialize/SqlStatisticProvider.java
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@@ -16,16 +16,41 @@
*/
package org.apache.calcite.materialize;
+import org.apache.calcite.plan.RelOptTable;
+
import java.util.List;
/**
* Estimates row counts for tables and columns.
*
* <p>Unlike {@link LatticeStatisticProvider}, works on raw tables and columns
* and does not need a {@link Lattice}.
+ *
+ * <p>It uses {@link org.apache.calcite.plan.RelOptTable} because that contains
+ * enough information to generate and execute SQL, while not being tied to a
+ * lattice.
*/
public interface SqlStatisticProvider {
- double tableCardinality(List<String> qualifiedTableName);
+ /** Returns an estimate of the number of rows in {@code table}. */
+ double tableCardinality(RelOptTable table);
+
+ /** Returns whether a join is a foreign key; that is, whether every row in
+ * the referencing table is matched by at least one row in the referenced
+ * table.
+ *
+ * <p>For example, {@code isForeignKey(EMP, [DEPTNO], DEPT, [DEPTNO])}
+ * returns true.
+ *
+ * <p>To change "at least one" to "exactly one", you also need to call
+ * {@link #isKey}. */
+ boolean isForeignKey(RelOptTable fromTable, List<Integer> fromColumns,
+ RelOptTable toTable, List<Integer> toColumns);
+
+ /** Returns whether a collection of columns is a unique key.
+ *
+ * <p>For example, {@code isKey(EMP, [DEPTNO]} returns true;
+ * <p>For example, {@code isKey(DEPT, [DEPTNO]} returns false. */
+ boolean isKey(RelOptTable table, List<Integer> columns);
}
Review comment:
Got it.
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