Struct Frame 

pub struct Frame {
    pub mode: Option<FrameMode>,
    pub start: Option<Expr>,
    pub end: Option<Expr>,
    pub exclusion: Option<FrameExclusion>,
}

A window frame: which rows around the current one the window function sees.

From PostgreSQL 17, https://www.postgresql.org/docs/17/sql-expressions.html#SYNTAX-WINDOW-FUNCTIONS:

{ RANGE | ROWS | GROUPS } frame_start [ frame_exclusion ]
{ RANGE | ROWS | GROUPS } BETWEEN frame_start AND frame_end [ frame_exclusion ]

frame_start, frame_end:
    UNBOUNDED PRECEDING | offset PRECEDING | CURRENT ROW
  | offset FOLLOWING    | UNBOUNDED FOLLOWING
frame_exclusion:
    EXCLUDE CURRENT ROW | EXCLUDE GROUP | EXCLUDE TIES | EXCLUDE NO OTHERS

Two defaults from that grammar are baked in, because they are what the keywords mean rather than what this library prefers:

• the mode defaults to RANGE, and
• frame_start defaults to UNBOUNDED PRECEDING.

So setting only exclusion still renders a complete frame, RANGE UNBOUNDED PRECEDING EXCLUDE TIES. BETWEEN appears exactly when there is an end bound — that is the whole difference between the two productions, and writing it without one is a syntax error.

bob carries a separate Defined bool that its setters flip, which can disagree with the fields. Here “defined” is derived: a frame is absent when all four parts are, which is also what makes Frame::default() render nothing.

Fields

mode: Option<FrameMode>

What the offsets count in. None renders as RANGE.

start: Option<Expr>

The start bound. None renders as UNBOUNDED PRECEDING.

end: Option<Expr>

The end bound. Its presence is what turns the frame into a BETWEEN.

exclusion: Option<FrameExclusion>

Rows to leave out of the frame even though they are inside it.

Implementations

impl Frame

pub fn new(mode: FrameMode) -> Self

A frame in mode, from UNBOUNDED PRECEDING.

pub fn set_mode(&mut self, mode: FrameMode)

Set the mode.

pub fn set_start(&mut self, start: impl IntoExpr)

Set the start bound.

pub fn set_end(&mut self, end: impl IntoExpr)

Set the end bound, making the frame a BETWEEN.

pub fn set_exclusion(&mut self, exclusion: FrameExclusion)

Set the exclusion.

pub fn is_empty(&self) -> bool

Whether no part of the frame was set, so that nothing will be written.

Trait Implementations

impl Clone for Frame

fn clone(&self) -> Frame

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Frame

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Frame

fn default() -> Frame

Returns the “default value” for a type.

impl Expression for Frame

fn write_sql(&self, w: &mut SqlWriter<'_>)

Append this fragment to w.

impl HasFrame for Frame

fn frame_mut(&mut self) -> &mut Frame

The frame to modify.