Struct SelectList 

pub struct SelectList {
    pub columns: Vec<Expr>,
    pub preload_columns: Vec<Expr>,
}

The projection: SELECT a, b, c, or * when nothing was asked for.

Preload columns are kept apart from the ones the caller selected so that a preloader can be an ordinary query mod while the mapper still knows how many of the returned columns belong to the root object — that is what count_select_cols is for. They render as one list, preloads last.

This is the one clause whose “absent” rendering is not empty: a SELECT with no list is not a statement, and * is what the grammar asks for. Absence is therefore still observable through is_empty.

Fields

columns: Vec<Expr>

What the caller selected.

preload_columns: Vec<Expr>

Columns a preloader added, rendered after columns.

Implementations

impl SelectList

pub fn count_select_cols(&self) -> usize

How many columns the caller selected, ignoring preloads.

pub fn set_select(&mut self, columns: impl IntoExprList)

Replace the selected columns.

pub fn append_select(&mut self, columns: impl IntoExprList)

Add to the selected columns.

pub fn set_preload_select(&mut self, columns: impl IntoExprList)

Replace the preload columns.

pub fn append_preload_select(&mut self, columns: impl IntoExprList)

Add to the preload columns.

pub fn append_column(&mut self, column: impl IntoExpr)

Add one column.

pub fn is_empty(&self) -> bool

Whether nothing was selected, so that * is what will be written.

Trait Implementations

impl Clone for SelectList

fn clone(&self) -> SelectList

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SelectList

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

Formats the value using the given formatter.

impl Default for SelectList

fn default() -> SelectList

Returns the “default value” for a type.

impl Expression for SelectList

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

Append this fragment to w.

impl HasSelectList for SelectList

fn select_list_mut(&mut self) -> &mut SelectList

The projection to modify.