About
Projection relational operator in Calcite is a relational operator.
Articles Related
Features
- name expressions using alias(expr, fieldName)
Example
final RelNode node = builder
.scan("EMP")
.project(builder.field("DEPTNO"), builder.field("ENAME"))
.build();
System.out.println(RelOptUtil.toString(node));
LogicalProject(DEPTNO=[$7], ENAME=[$1])
LogicalTableScan(table=[[scott, EMP]])
equivalent to:
SELECT ename, deptno
FROM scott.EMP;
builder.field create simple expressions that return the fields from the input relational expression (ie the TableScan) by ordinal (order)
- ie 7 (column at the position 7)
- and 1 (column at the position 1)