Struct QueryHints 

pub struct QueryHints {
    pub target_shards: Option<Vec<String>>,
    pub scatter_gather: bool,
    pub shard_key_value: Option<Value>,
    pub query_type: Option<String>,
}

Hints for query routing when a specific shard key isn’t available.

When executing queries that don’t have a clear shard key (e.g., range queries, aggregations), these hints help the ShardChooser decide which shards to query.

Fields

target_shards: Option<Vec<String>>

Specific shard names to target (if known).

scatter_gather: bool

Whether to query all shards (scatter-gather).

shard_key_value: Option<Value>

Optional shard key value extracted from query predicates.

query_type: Option<String>

Query type hint (e.g., “select”, “aggregate”, “count”).

Implementations

impl QueryHints

pub fn new() -> Self

Create empty hints (defaults to scatter-gather).

pub fn target(self, shards: Vec<String>) -> Self

Target specific shards by name.

pub fn scatter_gather(self) -> Self

Enable scatter-gather mode (query all shards).

pub fn with_shard_key(self, value: Value) -> Self

Provide a shard key value for routing.

pub fn query_type(self, query_type: impl Into<String>) -> Self

Set the query type hint.

Trait Implementations

impl Clone for QueryHints

fn clone(&self) -> QueryHints

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for QueryHints

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

Formats the value using the given formatter.

impl Default for QueryHints

fn default() -> QueryHints

Returns the “default value” for a type.