Struct BackendCapabilities 

pub struct BackendCapabilities {

    pub kind: BackendKind,
    pub transactions: TransactionSupport,
    pub row_locking: RowLocking,
    pub joins: bool,
    pub returning: bool,
    pub window_functions: bool,
    pub regex: bool,
    pub arrays: bool,
    pub distinct_on: bool,
    pub ilike: bool,
    pub statistical_aggregates: bool,
    pub max_params: usize,
    pub isolation_levels: &'static [IsolationLevel],
}

Declared capabilities of a backend.

Fields

kind: BackendKind

Backend family.

transactions: TransactionSupport

Transaction support level.

row_locking: RowLocking

Row-locking support level.

joins: bool

JOIN support.

returning: bool

RETURNING support.

window_functions: bool

Window function support.

regex: bool

Regex lookups.

arrays: bool

Native arrays.

distinct_on: bool

DISTINCT ON.

ilike: bool

Native ILIKE.

statistical_aggregates: bool

STDDEV / VARIANCE aggregates.

max_params: usize

Most bind parameters one statement may carry; bulk operations chunk their rows to stay below it.

isolation_levels: &'static [IsolationLevel]

Isolation levels that can be requested explicitly.

Implementations

impl BackendCapabilities

pub const fn postgres() -> Self

Capabilities of PostgreSQL (12+).

pub const fn sqlite() -> Self

Capabilities of SQLite (3.35+ for RETURNING, 3.25+ for windows).

SQLite has no row locking, no built-in REGEXP function and no STDDEV / VARIANCE. Its transactions are always serializable. The parameter limit is that of SQLite 3.32 and later.

pub const fn mysql() -> Self

Capabilities of MySQL 8.0.31+ (tested on 9.x).

• returning is true although MySQL has no RETURNING clause: the adapter emulates it (generated keys via LAST_INSERT_ID(), other writes by re-reading the affected rows in the same transaction).
• There is no DISTINCT ON, no native array type or array aggregate and no ILIKE (emulated with LOWER(..) LIKE LOWER(..)).
• Regex uses REGEXP_LIKE; row locking supports NOWAIT and SKIP LOCKED; all three isolation levels can be requested.

pub const fn mongodb() -> Self

Capabilities of MongoDB (5.0+; transactions need a replica set).

The plan is compiled to filters and aggregation pipelines: no joins, row locking, window functions, arrays, DISTINCT ON, subqueries, set operations or raw SQL. RETURNING is emulated by the adapter. Transactions are flat (no savepoints) and no isolation level can be requested. max_params bounds the rows per insert_many batch.

pub const fn redis() -> Self

Capabilities of Redis as a key, hash and set store.

Redis is not a QuerySet backend. Every relational feature is unsupported, so a plan checked against these capabilities fails with a BackendCapabilityError before any I/O. Multi-key atomicity is one MULTI/EXEC (TransactionSupport::Flat): there are no savepoints and no SQL isolation levels. max_params is 0 because Redis does not bind SQL parameters.

pub fn supports(&self, feature: Feature) -> bool

Whether feature is supported.

pub fn require(&self, feature: Feature) -> Result<(), BackendCapabilityError>

Return Ok(()) if feature is supported, otherwise a typed error.

Trait Implementations

impl Clone for BackendCapabilities

fn clone(&self) -> BackendCapabilities

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for BackendCapabilities

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

Formats the value using the given formatter.

impl Eq for BackendCapabilities

impl PartialEq for BackendCapabilities

fn eq(&self, other: &BackendCapabilities) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for BackendCapabilities