sq/libsq/ast/range.go
Neil O'Toole 44d27207f8
: column-only queries ()
* Column-only queries
2023-06-17 19:28:11 -06:00

121 lines
2.9 KiB
Go

package ast
import (
"strconv"
"github.com/neilotoole/sq/libsq/ast/internal/slq"
)
// RowRangeNode models a range, effectively {OFFSET,LIMIT}.
type RowRangeNode struct {
baseNode
Offset int
Limit int
}
func newRowRangeNode(ctx *slq.RowRangeContext, offset, limit int) *RowRangeNode {
rr := &RowRangeNode{}
rr.ctx = ctx
rr.text = ctx.GetText()
rr.Offset = offset
rr.Limit = limit
return rr
}
// String implements ast.Node.
func (rr *RowRangeNode) String() string {
return rr.Text()
}
// Range returns the offset and limit.
func (rr *RowRangeNode) Range() (offset, limit int) {
offset = rr.Offset
limit = rr.Limit
return offset, limit
}
// SetParent implements ast.Node.
func (rr *RowRangeNode) SetParent(parent Node) error {
seg, ok := parent.(*SegmentNode)
if !ok {
return errorf("%T requires parent of type *%s", rr, typeSegmentNode)
}
rr.parent = seg
return nil
}
// VisitRowRange implements slq.SLQVisitor.
func (v *parseTreeVisitor) VisitRowRange(ctx *slq.RowRangeContext) any {
// [] select all rows (no range)
// [1] select row[1]
// [10:15] select rows 10 thru 15
// [0:15] select rows 0 thru 15
// [:15] same as above (0 thru 15)
// [10:] select all rows from 10 onwards
if ctx.COLON() == nil && len(ctx.AllNN()) == 0 {
// [] select all rows, aka no range
return nil
}
if ctx.COLON() == nil {
// [1] -- select row[1]
if len(ctx.AllNN()) != 1 {
return errorf("row range: expected one integer but got %d", len(ctx.AllNN()))
}
i, _ := strconv.Atoi(ctx.AllNN()[0].GetText())
rr := newRowRangeNode(ctx, i, 1)
return v.cur.AddChild(rr)
}
// there's a colon... can only be one or two ints
if len(ctx.AllNN()) > 2 {
return errorf("row range: expected one or two integers but got %d", len(ctx.AllNN()))
}
if len(ctx.AllNN()) == 2 {
// [10:15] -- select rows 10 thru 15
offset, _ := strconv.Atoi(ctx.AllNN()[0].GetText())
finish, _ := strconv.Atoi(ctx.AllNN()[1].GetText())
limit := finish - offset
rr := newRowRangeNode(ctx, offset, limit)
return v.cur.AddChild(rr)
}
// it's one of these two cases:
// [:15] (0 thru 15)
// [10:] select all rows from 10 onwards
// so we need to determine if the INT is before or after the colon
var offset int
limit := -1
if ctx.COLON().GetSymbol().GetTokenIndex() < ctx.AllNN()[0].GetSymbol().GetTokenIndex() {
// [:15] (0 thru 15)
offset = 0
limit, _ = strconv.Atoi(ctx.AllNN()[0].GetText())
} else {
// [10:] select all rows from 10 onwards
offset, _ = strconv.Atoi(ctx.AllNN()[0].GetText())
}
rr := newRowRangeNode(ctx, offset, limit)
return v.cur.AddChild(rr)
}
// verifyRowRange validates the RowRangeNode element.
func verifyRowRange(w *Walker, node Node) error {
rr, ok := node.(*RowRangeNode)
if !ok {
return errorf("expected %s but got %T", typeRowRangeNode, node)
}
if w.state != nil {
return errorf("only one row range element permitted")
}
w.state = rr
// TODO: check that the row range is after a selectable
return nil
}