Struct BlobDecl 

pub struct BlobDecl {
    pub id_column: String,
    pub size_column: String,
    pub hash_column: String,
    pub namespace: String,
    pub cloud_path_column: Option<String>,
    pub scope: BlobScope,
    pub provenance: Provenance,
    pub fill: CacheFill,
    pub replacement: BlobReplacement,
}

Where a blob-bearing table’s blob columns live, declared by the host so coven can derive every blob a row references without a runtime callback. Resolved against the live schema into a [crate::blob::decl::BlobDecls] each cycle.

A blob declares two orthogonal properties: provenance (its Local story) and fill (its Remote story).

Fields

id_column: String

The column holding the blob id. Defaults to the primary key (id, column 0), which is the blob id for most tables.

size_column: String

The column holding the blob’s plaintext length in bytes.

hash_column: String

The column holding the blob’s content hash — the lowercase-hex SHA-256 of its plaintext, computed at import (see [crate::blob::content_hash]). The row carries it in a signed changeset, so it is signed by the row’s author; on download coven hashes the decrypted plaintext and requires equality with this value, so the bytes are pinned by the author, not by where they were found. Defaults to hash.

namespace: String

Cloud namespace for the blob, e.g. "images" or "audio".

cloud_path_column: Option<String>

The column holding the consumer’s readable cloud-relative path, used as the object key under the plain (browsable) blob-path scheme. None means the blob is keyed only by its hashed id (the default obfuscated scheme).

scope: BlobScope

How the blob is scoped for encryption (see crate::blob::BlobScope).

provenance: Provenance

The blob’s Local story: crate::blob::Provenance::UserProvided (the user’s file at a path) or crate::blob::Provenance::HostProvided (coven’s own copy in the local store).

fill: CacheFill

The blob’s Remote story: crate::blob::CacheFill::CacheEager (fetched into the cache on every pull) or crate::blob::CacheFill::CacheLazy (fetched into the cache on first read).

replacement: BlobReplacement

The blob’s replacement story: whether this row may be repointed at a different blob (crate::blob::BlobReplacement). Decides what coven requires of the blob’s cloud key so that a cloud object is never rewritten with different bytes. Defaults to crate::blob::BlobReplacement::Replaceable.

Implementations

impl BlobDecl

pub fn new( namespace: impl Into<String>, provenance: Provenance, fill: CacheFill, ) -> BlobDecl

A blob declaration in namespace with the given provenance (its Local story) and cache fill (its Remote story), the blob id taken from the primary key (id), no readable cloud path, master-scoped, and Replaceable. Refine with the with_* builders.

pub fn write_once(self) -> BlobDecl

Declare that this table’s row is never repointed at a different blob (crate::blob::BlobReplacement::WriteOnce), which frees its readable cloud_path to be a stable, fully human-readable name. coven refuses a repointing. Read that variant’s docs before reaching for this: it is a weaker contract than the default, and it asks the consumer to guarantee the part coven cannot see — that a path is never reused by a different blob.

pub fn with_id_column(self, column: impl Into<String>) -> BlobDecl

Take the blob id from column instead of the primary key.

pub fn with_size_column(self, column: impl Into<String>) -> BlobDecl

Take the plaintext byte length from column instead of size.

pub fn with_hash_column(self, column: impl Into<String>) -> BlobDecl

Take the content hash from column instead of hash.

pub fn with_cloud_path_column(self, column: impl Into<String>) -> BlobDecl

Key the blob at the readable cloud path in column (the plain scheme).

pub fn with_scope(self, scope: BlobScope) -> BlobDecl

Scope the blob’s encryption (defaults to crate::blob::BlobScope::Master).

Trait Implementations

impl Clone for BlobDecl

fn clone(&self) -> BlobDecl

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for BlobDecl

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

Formats the value using the given formatter.

impl PartialEq for BlobDecl

fn eq(&self, other: &BlobDecl) -> 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 Eq for BlobDecl

impl StructuralPartialEq for BlobDecl