Method selectFrom

compiler/semantic/sql.go:297–325

selectFrom analyzes the FROM clause which is a cross-joined set of table expressions. inType is from the immediate pipe parent in a top-level select, nil otherwise

(loc ast.Loc, from ast.SQLTableExpr, seq sem.Seq, inType super.Type)

// selectFrom analyzes the FROM clause which is a cross-joined set of table expressions.
// inType is from the immediate pipe parent in a top-level select, nil otherwise
func (t *translator) selectFrom(loc ast.Loc, from ast.SQLTableExpr, seq sem.Seq, inType super.Type) (sem.Seq, relScope) {
	if from == nil {
		// No FROM clause means the pipe parent is providing input in which
		// case inType is the type of that input, or there is no input at all,
		// in which case we should model an empty table.
		if inType == nil || inType == super.TypeNull {
			// Model no or null input as an input table so that column checks fail.
			return seq, newTableFromType(t.sctx.MustLookupTypeRecord([]super.Field{}), t.checker.unknown)
		}
		return seq, newTableFromType(inType, t.checker.unknown)
	}
	off := len(seq)
	hasParent := off > 0
	seq, scope := t.sqlTableExpr(from, seq)
	if off >= len(seq) {
		// The chain didn't get lengthed so semFrom must have encountered
		// an error...
		return seq, badTable
	}
	// If we have parents with both a from and select, report an error but
	// only if it's not a RobotScan where the parent feeds the from operateor.
	if _, ok := seq[off].(*sem.RobotScan); !ok {
		if hasParent {
			t.error(loc, errors.New("SELECT cannot have both an embedded FROM clause and input from parents"))
			return append(seq, badOp), badTable
		}
	}
	return seq, scope
}

// sqlValues analyzes the values expression which currently cannot depend
// on the input data (until we add support for lateral joins; then a values