Struct SessionVar

pub struct SessionVar {
    definition: VarDefinition,
    default_value: Option<Box<dyn Value>>,
    local_value: Option<Box<dyn Value>>,
    staged_value: Option<Box<dyn Value>>,
    session_value: Option<Box<dyn Value>>,
}

A SessionVar is the session value for a configuration parameter. If unset, the server default is used instead.

Note: even though all of the different *_value fields are Box<dyn Value> they are enforced to be the same type because we use the definitions parse(...) method. This is guaranteed to return the same type as the compiled in default.

Fields

definition: VarDefinition

default_value: Option<Box<dyn Value>>

System or Role default value.

local_value: Option<Box<dyn Value>>

Value LOCAL to a transaction, will be unset at the completion of the transaction.

staged_value: Option<Box<dyn Value>>

Value set during a transaction, will be set if the transaction is committed.

session_value: Option<Box<dyn Value>>

Value that overrides the default.

Implementations

impl SessionVar

pub const fn new(var: VarDefinition) -> Self

pub fn check(&self, input: VarInput<'_>) -> Result<String, VarError>

Checks if the provided VarInput is valid for the current session variable, returning the formatted output if it’s valid.

pub fn set(&mut self, input: VarInput<'_>, local: bool) -> Result<(), VarError>

Parse the input and update the stored value to match.

pub fn set_default(&mut self, input: VarInput<'_>) -> Result<(), VarError>

Sets the default value for the variable.

pub fn reset(&mut self, local: bool)

Reset the stored value to the default.

pub fn end_transaction(&self, action: EndTransactionAction) -> Option<Self>

Returns a possibly new SessionVar if this needs to mutate at transaction end.

pub fn is_mutating(&self) -> bool

Whether this Var needs to mutate at the end of a transaction.

pub fn value_dyn(&self) -> &dyn Value

pub fn inspect_session_value(&self) -> Option<&dyn Value>

Returns the Value that is currently stored as the session_value.

Note: This should only be used for inspection, if you want to determine the current value of this SessionVar you should use SessionVar::value.

fn validate_constraints(&self, val: &dyn Value) -> Result<(), VarError>

Trait Implementations

impl Clone for SessionVar

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SessionVar

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

Formats the value using the given formatter.

impl Var for SessionVar

fn name(&self) -> &'static str

Returns the name of the configuration parameter.

fn value(&self) -> String

Constructs a flattened string representation of the current value of the configuration parameter.

fn description(&self) -> &'static str

Returns a short sentence describing the purpose of the configuration parameter.

fn type_name(&self) -> Cow<'static, str>

Returns the name of the type of this variable.

fn visible(&self, user: &User, system_vars: &SystemVars) -> Result<(), VarError>

Indicates wither the Var is visible as a function of the user and system_vars. “Invisible” parameters return VarErrors.

fn is_unsafe(&self) -> bool

Reports whether the variable is only visible in unsafe mode.

fn as_var(&self) -> &dyn Var

where Self: Sized,

Upcast self to a dyn Var, useful when working with multiple different implementors of Var.