Examples with SqlValuesOperator org.apache.calcite.sql.SqlValuesOperator used on opensource projects

Example 1 with SqlValuesOperator

use of org.apache.calcite.sql.SqlValuesOperator in project calcite by apache.

the class SqlToRelConverter method convertToSingleValueSubq.

/**
 * Converts the RelNode tree for a select statement to a select that
 * produces a single value.
 *
 * @param query the query
 * @param plan   the original RelNode tree corresponding to the statement
 * @return the converted RelNode tree
 */
public RelNode convertToSingleValueSubq(SqlNode query, RelNode plan) {
    // Check whether query is guaranteed to produce a single value.
    if (query instanceof SqlSelect) {
        SqlSelect select = (SqlSelect) query;
        SqlNodeList selectList = select.getSelectList();
        SqlNodeList groupList = select.getGroup();
        if ((selectList.size() == 1) && ((groupList == null) || (groupList.size() == 0))) {
            SqlNode selectExpr = selectList.get(0);
            if (selectExpr instanceof SqlCall) {
                SqlCall selectExprCall = (SqlCall) selectExpr;
                if (Util.isSingleValue(selectExprCall)) {
                    return plan;
                }
            }
            // it is ensured to produce a single value
            if (select.getFetch() != null && select.getFetch() instanceof SqlNumericLiteral) {
                SqlNumericLiteral limitNum = (SqlNumericLiteral) select.getFetch();
                if (((BigDecimal) limitNum.getValue()).intValue() < 2) {
                    return plan;
                }
            }
        }
    } else if (query instanceof SqlCall) {
        // If the query is (values ...),
        // it is necessary to look into the operands to determine
        // whether SingleValueAgg is necessary
        SqlCall exprCall = (SqlCall) query;
        if (exprCall.getOperator() instanceof SqlValuesOperator && Util.isSingleValue(exprCall)) {
            return plan;
        }
    }
    // If not, project SingleValueAgg
    return RelOptUtil.createSingleValueAggRel(cluster, plan);
}