Struct Schema 

pub struct Schema { /* private fields */ }

Document schema definition for Anda DB.

A Schema describes:

• which fields a document may contain (by name and type),
• their stable on-disk indexes (FieldEntry::idx), and
• a monotonic version used to coordinate schema migrations.

Every schema implicitly contains the reserved _id field of type FieldType::U64 with idx == 0 (see Schema::ID_KEY). It is added automatically by SchemaBuilder::new.

Schema is Serialize / Deserialize and round-trips through both JSON and CBOR. Deserialization re-validates every invariant (_id presence, unique field names and indexes, valid field name characters, idx <= u16::MAX) so it is safe to load schemas coming from untrusted storage.

Implementations

impl Schema

pub const ID_KEY: &'static str = "_id"

The key name for the ID field. it is a special u64 field used as an internal unique identifier in a collection. It is always present in the schema with idx 0.

pub fn version(&self) -> u64

Returns the schema version.

pub fn with_version(&mut self, version: u64) -> &mut Schema

Sets the schema version.

pub fn needs_upgrade(&self, other: &Schema) -> bool

Returns true if self has a higher version than other, indicating that a schema migration is needed.

pub fn upgrade_with(&mut self, old: &Schema) -> Result<(), SchemaError>

Upgrades this schema using field indexes from an older persisted schema.

The new schema (self) is typically built from program code where field indexes are assigned sequentially. The old schema comes from persistent storage with fixed indexes. This method ensures index consistency by:

1. For fields present in both schemas: inherits the idx from the old schema, and verifies the field type has not changed (type changes are not allowed).
2. For new fields (in self but not in old): assigns fresh indexes starting from max(old indexes) + 1, ensuring no conflicts with any old index.
3. For removed fields (in old but not in self): their indexes are simply not reused, preventing data corruption.

Arguments

• old - The old schema loaded from persistent storage.

Errors

• If self.version is not greater than old.version.
• If a field that exists in both schemas has a different type.

pub fn builder() -> SchemaBuilder

Creates a new SchemaBuilder instance.

Returns

A new SchemaBuilder with default settings.

pub fn len(&self) -> usize

Returns the number of fields in the schema. This includes the “_id” field and any other fields defined in the schema.

Returns

The number of fields.

pub fn is_empty(&self) -> bool

Checks if the schema has no fields.

Returns

true if the schema has no fields, false otherwise.

pub fn get_field(&self, name: &str) -> Option<&FieldEntry>

Gets a field by name.

Arguments

• name - The name of the field to get.

Returns

Some(&FieldEntry) if the field exists, None otherwise.

pub fn get_field_or_err(&self, name: &str) -> Result<&FieldEntry, SchemaError>

Gets a field by name or returns an error if it doesn’t exist.

Arguments

• name - The name of the field to get.

Returns

Ok(&FieldEntry) if the field exists, Err(SchemaError) otherwise.

pub fn iter(&self) -> impl Iterator<Item = &FieldEntry>

Returns an iterator over all fields in the schema.

Returns

An iterator yielding references to FieldEntry.

pub fn validate( &self, values: &BTreeMap<usize, FieldValue>, ) -> Result<(), SchemaError>

Validates a set of field values against this schema.

Arguments

• values - The field values to validate.

Returns

Ok(()) if validation succeeds, Err(SchemaError) otherwise.

Errors

Returns an error if:

• A field index in values doesn’t exist in the schema
• A required field is missing
• A field value doesn’t match the field type

Trait Implementations

impl Clone for Schema

fn clone(&self) -> Schema

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Schema

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Schema

fn deserialize<D>( deserializer: D, ) -> Result<Schema, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Schema

fn eq(&self, other: &Schema) -> 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 Serialize for Schema

fn serialize<S>( &self, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for Schema

impl StructuralPartialEq for Schema