evoq_read_model behaviour (evoq v1.12.0)

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Read model store behavior for evoq.

Provides an abstract interface for read model storage. Projections use this behavior to persist query-optimized data.

Design Principles

- Read models are optimized for queries (no joins, no calculations) - All calculations happen in projections, not queries - Read models can be rebuilt from events at any time

Callbacks

Required: - init(Config) -> {ok, State} - get(Key, State) -> {ok, Value} | {error, not_found} - put(Key, Value, State) -> {ok, NewState} - delete(Key, State) -> {ok, NewState}

Optional: - list(Prefix, State) -> {ok, [{Key, Value}]} - clear(State) -> {ok, NewState}

Summary

Types

read_model/0

Callbacks

clear/1
delete/2
get/2
init/1
list/2
put/3

Functions

clear(Read_model)

Clear all data from the read model.

delete(Key, Read_model)

Delete a value from the read model.

get(Key, Read_model)

Get a value from the read model.

get_checkpoint(Read_model)

Get the current checkpoint position.

list(Prefix, Read_model)

List all key-value pairs matching a prefix.

new(Module, Config)

Create a new read model instance.

put(Key, Value, Read_model)

Put a value into the read model.

set_checkpoint(Position, RM)

Set the checkpoint position.

Types

read_model/0

-opaque read_model()

Callbacks

clear/1

(optional) 
-callback clear(State :: term()) -> {ok, NewState :: term()} | {error, Reason :: term()}.

delete/2

-callback delete(Key :: term(), State :: term()) -> {ok, NewState :: term()} | {error, Reason :: term()}.

get/2

-callback get(Key :: term(), State :: term()) ->
                 {ok, Value :: term()} | {error, not_found} | {error, Reason :: term()}.

init/1

-callback init(Config :: map()) -> {ok, State :: term()} | {error, Reason :: term()}.

list/2

(optional) 
-callback list(Prefix :: term(), State :: term()) ->
                  {ok, [{Key :: term(), Value :: term()}]} | {error, Reason :: term()}.

put/3

-callback put(Key :: term(), Value :: term(), State :: term()) ->
                 {ok, NewState :: term()} | {error, Reason :: term()}.

Functions

clear(Read_model)

-spec clear(read_model()) -> {ok, read_model()} | {error, term()}.

Clear all data from the read model.

delete(Key, Read_model)

-spec delete(term(), read_model()) -> {ok, read_model()} | {error, term()}.

Delete a value from the read model.

get(Key, Read_model)

-spec get(term(), read_model()) -> {ok, term()} | {error, not_found | term()}.

Get a value from the read model.

get_checkpoint(Read_model)

-spec get_checkpoint(read_model()) -> non_neg_integer().

Get the current checkpoint position.

list(Prefix, Read_model)

-spec list(term(), read_model()) -> {ok, [{term(), term()}]} | {error, term()}.

List all key-value pairs matching a prefix.

new(Module, Config)

-spec new(atom(), map()) -> {ok, read_model()} | {error, term()}.

Create a new read model instance.

put(Key, Value, Read_model)

-spec put(term(), term(), read_model()) -> {ok, read_model()} | {error, term()}.

Put a value into the read model.

set_checkpoint(Position, RM)

-spec set_checkpoint(non_neg_integer(), read_model()) -> read_model().

Set the checkpoint position.