Struct QueryHash

pub struct QueryHash { /* private fields */ }

A hash for uniquely identifying query execution units, to avoid recompilation of queries that have an open subscription.

Currently we are using a cryptographic hash, which is most certainly overkill. However the benefits include uniqueness by definition, and a compact representation for equality comparisons.

It also decouples the hash from the physical plan.

Note that we could hash QueryExprs directly, using the standard library’s hasher. However some execution units are comprised of several query plans, as is the case for incremental joins. And we want to associate a hash with the entire unit of execution, rather than an individual plan.

Implementations

impl QueryHash

pub const NONE: Self

The zero value of a QueryHash

pub const MIN: Self = Self::NONE

The min value of a QueryHash

pub const MAX: Self

The max value of a QueryHash

pub fn from_bytes(bytes: &[u8]) -> Self

pub fn from_string(str: &str, identity: Identity, has_param: bool) -> Self

Generate a hash from a query string

pub fn from_string_and_identity(str: &str, identity: Identity) -> Self

If a query is parameterized with :sender, we must use the value of :sender, i.e. the identity of the caller, when hashing the query text, so that two identical queries from different clients aren’t hashed to the same value.

TODO: Once we have RLS, this hash must computed after name resolution. It can no longer be computed from the source text.

Trait Implementations

impl Clone for QueryHash

fn clone(&self) -> QueryHash

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for QueryHash

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

Formats the value using the given formatter.

impl From<QueryHash> for u256

fn from(hash: QueryHash) -> Self

Converts to this type from the input type.

impl Hash for QueryHash

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for QueryHash

fn cmp(&self, other: &QueryHash) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for QueryHash

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for QueryHash

fn partial_cmp(&self, other: &QueryHash) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for QueryHash

impl Eq for QueryHash

impl StructuralPartialEq for QueryHash