org.apache.calcite.materialize

Interface SqlStatisticProvider

All Known Implementing Classes:

CachingSqlStatisticProvider, MapSqlStatisticProvider, QuerySqlStatisticProvider

public interface SqlStatisticProvider

Estimates row counts for tables and columns, and whether combinations of columns form primary/unique and foreign keys.

Unlike LatticeStatisticProvider, works on raw tables and columns and does not need a Lattice.

It uses RelOptTable because that contains enough information to generate and execute SQL, while not being tied to a lattice.

The main implementation, QuerySqlStatisticProvider, executes queries on a populated database. Implementations that use database statistics (from ANALYZE TABLE, etc.) and catalog information (e.g. primary and foreign key constraints) would also be possible.

Method Summary

Modifier and Type	Method and Description
boolean	isForeignKey(RelOptTable fromTable, List<Integer> fromColumns, RelOptTable toTable, List<Integer> toColumns) 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.
boolean	isKey(RelOptTable table, List<Integer> columns) Returns whether a collection of columns is a unique (or primary) key.
double	tableCardinality(RelOptTable table) Returns an estimate of the number of rows in table.

Method Detail

tableCardinality

double tableCardinality(RelOptTable table)

Returns an estimate of the number of rows in table.

isForeignKey

boolean isForeignKey(RelOptTable fromTable,
                     List<Integer> fromColumns,
                     RelOptTable toTable,
                     List<Integer> toColumns)

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.

For example, isForeignKey(EMP, [DEPTNO], DEPT, [DEPTNO]) returns true.

To change "at least one" to "exactly one", you also need to call isKey(org.apache.calcite.plan.RelOptTable, java.util.List<java.lang.Integer>).

isKey

boolean isKey(RelOptTable table,
              List<Integer> columns)

Returns whether a collection of columns is a unique (or primary) key.

For example, isKey(EMP, [DEPTNO] returns true;

For example, isKey(DEPT, [DEPTNO] returns false.