Struct PreparedStatement 

pub struct PreparedStatement<'conn> { /* private fields */ }

A handle to a server-side prepared statement.

Construct via Connection::prepare or Connection::prepare_typed. Holding this type keeps the statement allocated on the server; it is released automatically when the handle is dropped.

Reuse

A single PreparedStatement can be executed many times with different parameter values — the server caches the parsed plan. This is the primary reason to use prepared statements over Connection::query_params for loops over user input.

Implementations

impl<'conn> PreparedStatement<'conn>

pub fn param_count(&self) -> usize

Returns the number of parameters the statement expects.

pub fn param_types(&self) -> &[Oid]

Returns the parameter type OIDs (as the server inferred or the caller explicitly passed to Connection::prepare_typed).

pub fn schema(&self) -> &ResultSchema

Returns the result-column schema. Always available — it was captured during the Parse/Describe at prepare time.

pub fn sql(&self) -> &str

The original SQL text.

pub fn query(&self, params: &[&dyn ToSqlParam]) -> Result<Rowset<'conn>>

Executes the statement and returns a streaming Rowset.

Memory stays bounded to one chunk regardless of result size — the prepared-statement equivalent of Connection::execute_query.

Errors

• Returns Error::Other if the underlying Connection is on gRPC transport (prepared statements are TCP-only).
• Returns Error::Client if the server rejects Bind or Execute (type mismatch, runtime error while streaming).
• Returns Error::Io on transport-level I/O failures.

pub fn execute(&self, params: &[&dyn ToSqlParam]) -> Result<u64>

Executes the statement as a command (INSERT / UPDATE / DELETE / DDL) and returns the affected-row count.

Errors

• Returns Error::Other on gRPC transport.
• Returns Error::Client if the server rejects Bind or Execute.
• Returns Error::Io on transport-level I/O failures.

pub fn fetch_one(&self, params: &[&dyn ToSqlParam]) -> Result<Row>

Fetches exactly one row; errors if the result is empty.

Errors

• Returns the error from query.
• Returns Error::Other with message "Query returned no rows" if the result is empty.

pub fn fetch_optional(&self, params: &[&dyn ToSqlParam]) -> Result<Option<Row>>

Fetches at most one row; returns None if the result is empty.

Errors

Returns the error from query; an empty result yields Ok(None).

pub fn fetch_all(&self, params: &[&dyn ToSqlParam]) -> Result<Vec<Row>>

Fetches every row into a Vec.

Errors

Returns the error from query, or a transport error produced while draining every chunk.

pub fn fetch_scalar<T: RowValue>(&self, params: &[&dyn ToSqlParam]) -> Result<T>

Fetches a single non-NULL scalar; errors on empty / NULL.

Errors

• Returns the error from query.
• Returns Error::Other with message "Query returned no rows" if the result is empty.
• Returns Error::Other with message "Scalar query returned NULL" if the first cell is SQL NULL.

pub fn fetch_optional_scalar<T: RowValue>( &self, params: &[&dyn ToSqlParam], ) -> Result<Option<T>>

Fetches a single scalar, allowing NULL as None.

Errors

Returns the error from query. An empty result still errors (see fetch_scalar); SQL NULL yields Ok(None).

Trait Implementations

impl<'conn> Debug for PreparedStatement<'conn>

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

Formats the value using the given formatter.