sq/libsq/ast/process.go

package ast

// narrowTblSel takes a generic selector, and if appropriate, converts it
// to an *ast.TblSelectorNode.
func narrowTblSel(_ *Walker, node Node) error {
	// node is guaranteed to be a selector node
	sel, ok := node.(*SelectorNode)
	if !ok {
		return errorf("expected %T but got %T", sel, node)
	}

	seg, ok := sel.Parent().(*SegmentNode)
	if !ok {
		return nil
	}

	var (
		tblSel *TblSelectorNode
		err    error
	)

	if seg.SegIndex() == 0 {
		// If this is the first segment, then the selector MUST refer
		// to a table. E.g.
		//
		//  $ sq '.data'
		//
		// ".data" must be a table.
		if tblSel, err = newTblSelector(sel); err != nil {
			return err
		}

		return nodeReplace(sel, tblSel)
	}

	prevType, err := seg.Prev().ChildType()
	if err != nil {
		return err
	}

	if prevType == typeHandleNode {
		var handleNode *HandleNode
		if handleNode, ok = seg.Prev().Children()[0].(*HandleNode); !ok {
			return errorf("syntax error: expected %T, but got %T", handleNode, seg.Prev().Children()[0])
		}

		// this means that this selector must be a table selector
		if tblSel, err = newTblSelector(sel); err != nil {
			return err
		}
		tblSel.handle = handleNode.Text()
		return nodeReplace(sel, tblSel)
	}

	return nil
}

// narrowTblColSel takes a generic selector, and if appropriate, replaces it
// with a TblColSelectorNode.
func narrowTblColSel(w *Walker, node Node) error {
	// node is guaranteed to be type SelectorNode
	sel, ok := node.(*SelectorNode)
	if !ok {
		return errorf("expected %T but got %T", sel, node)
	}

	parent := sel.Parent()
	switch parent := parent.(type) {
	case *JoinConstraint, *FuncNode, *OrderByTermNode, *GroupByNode, *ExprNode:
		if sel.name1 == "" {
			return nil
		}

		tblColSelNode, err := newTblColSelectorNode(sel)
		if err != nil {
			return err
		}
		return nodeReplace(sel, tblColSelNode)
	case *SegmentNode:
		// if the parent is a segment, this is a "top-level" selector.
		// Only top-level selectors after the final tabler seg are
		// convert to TblColSelectorNode.
		tablerSeg, err := NewInspector(w.root.(*AST)).FindFinalTablerSegment()
		if err != nil {
			return err
		}

		if parent.SegIndex() <= tablerSeg.SegIndex() {
			// Skipping this selector because it's not after the final selectable segment
			return nil
		}

		if sel.name1 == "" {
			// It's only a TblColSelectorNode if name1 is set.
			// So, it's either a ColSelectorNode or a TblSelectorNode.
			return nil
		}

		tblColSelNode, err := newTblColSelectorNode(sel)
		if err != nil {
			return err
		}
		return nodeReplace(sel, tblColSelNode)

	default:
	}

	return nil
}

// narrowColSel takes a generic selector, and if appropriate, converts it to a ColSel.
func narrowColSel(w *Walker, node Node) error {
	// node is guaranteed to be type SelectorNode
	sel, ok := node.(*SelectorNode)
	if !ok {
		return errorf("expected %T but got %T", sel, node)
	}

	parent := sel.Parent()

	switch parent := parent.(type) {
	case *JoinConstraint, *FuncNode, *OrderByTermNode, *GroupByNode, *ExprNode:
		colSel, err := newColSelectorNode(sel)
		if err != nil {
			return err
		}
		return nodeReplace(sel, colSel)
	case *SegmentNode:
		// if the parent is a segment, this is a "top-level" selector.
		// Only top-level selectors after the final tabler seg are
		// convert to colSels.
		tablerSeg, err := NewInspector(w.root.(*AST)).FindFinalTablerSegment()
		if err != nil {
			return err
		}

		if parent.SegIndex() <= tablerSeg.SegIndex() {
			// Skipping this selector because it's not after the final selectable segment
			return nil
		}

		colSel, err := newColSelectorNode(sel)
		if err != nil {
			return err
		}
		return nodeReplace(sel, colSel)

	default:
		// Skipping this selector, as parent is not of a relevant type
	}

	return nil
}

// determineJoinTables attempts to determine the tables that a JOIN refers to.
func determineJoinTables(_ *Walker, node Node) error {
	// node is guaranteed to be FnJoin
	fnJoin, ok := node.(*JoinNode)
	if !ok {
		return errorf("expected *FnJoin but got %T", node)
	}

	seg, ok := fnJoin.Parent().(*SegmentNode)
	if !ok {
		return errorf("JOIN() must have a *SegmentNode parent, but got %T", fnJoin.Parent())
	}

	prevSeg := seg.Prev()
	if prevSeg == nil {
		return errorf("JOIN() must not be in the first segment")
	}

	if len(prevSeg.Children()) != 2 || len(nodesWithType(prevSeg.Children(), typeTblSelectorNode)) != 2 {
		return errorf("JOIN() must have two table selectors in the preceding segment")
	}

	fnJoin.leftTbl, ok = prevSeg.Children()[0].(*TblSelectorNode)
	if !ok {
		return errorf("JOIN() expected table selector in previous segment, but was %T(%s)", prevSeg.Children()[0],
			prevSeg.Children()[0].Text())
	}
	fnJoin.rightTbl, ok = prevSeg.Children()[1].(*TblSelectorNode)
	if !ok {
		return errorf("JOIN() expected table selector in previous segment, but was %T(%s)", prevSeg.Children()[1],
			prevSeg.Children()[1].Text())
	}
	return nil
}