# messengyr v0.0.1 Messengyr.Repo

# Summary

## Functions

aggregate(queryable, aggregate, field, opts \\ [])

Calculate the given `aggregate` over the given `field`

all(queryable, opts \\ [])

Fetches all entries from the data store matching the given query

config()

Returns the adapter configuration stored in the `:otp_app` environment

delete(struct, opts \\ [])

Deletes a struct using its primary key

delete!(struct, opts \\ [])

Same as `delete/2` but returns the struct or raises if the changeset is invalid

delete_all(queryable, opts \\ [])

Deletes all entries matching the given query

get(queryable, id, opts \\ [])

Fetches a single struct from the data store where the primary key matches the given id

get!(queryable, id, opts \\ [])

Similar to `get/3` but raises `Ecto.NoResultsError` if no record was found

get_by(queryable, clauses, opts \\ [])

Fetches a single result from the query

get_by!(queryable, clauses, opts \\ [])

Similar to `get_by/3` but raises `Ecto.NoResultsError` if no record was found

in_transaction?()

Returns true if the current process is inside a transaction

init(, opts)

Dynamically loads the repository url from the DATABASE_URL environment variable

insert(struct, opts \\ [])

Inserts a struct or a changeset

insert!(struct, opts \\ [])

Same as `insert/2` but returns the struct or raises if the changeset is invalid

insert_all(schema_or_source, entries, opts \\ [])

Inserts all entries into the repository

insert_or_update(changeset, opts \\ [])

Inserts or updates a changeset depending on whether the struct is persisted or not

insert_or_update!(changeset, opts \\ [])

Same as `insert_or_update/2` but returns the struct or raises if the changeset is invalid

load(schema_or_types, data)

Loads `data` into a struct or a map

one(queryable, opts \\ [])

Fetches a single result from the query

one!(queryable, opts \\ [])

Similar to `one/2` but raises `Ecto.NoResultsError` if no record was found

preload(struct_or_structs, preloads, opts \\ [])

Preloads all associations on the given struct or structs

query(sql, params \\ [], opts \\ [])

A convenience function for SQL-based repositories that executes the given query

query!(sql, params \\ [], opts \\ [])

A convenience function for SQL-based repositories that executes the given query

rollback(value)

Rolls back the current transaction

start_link(opts \\ [])

Starts any connection pooling or supervision and return `{:ok, pid}` or just `:ok` if nothing needs to be done

stop(pid, timeout \\ 5000)

Shuts down the repository represented by the given pid

stream(queryable, opts \\ [])

Returns a lazy enumerable that emits all entries from the data store matching the given query. SQL adapters, such as Postgres and MySQL, can only enumerate a stream inside a transaction

transaction(fun_or_multi, opts \\ [])

Runs the given function or `Ecto.Multi` inside a transaction

update(struct, opts \\ [])

Updates a changeset using its primary key

update!(struct, opts \\ [])

Same as `update/2` but returns the struct or raises if the changeset is invalid

update_all(queryable, updates, opts \\ [])

Updates all entries matching the given query with the given values

# Functions

aggregate(queryable, aggregate, field, opts \\ [])

Calculate the given `aggregate` over the given `field`.

If the query has a limit, offset or distinct set, it will be automatically wrapped in a subquery in order to return the proper result.

Any preload or select in the query will be ignored in favor of the column being aggregated.

The aggregation will fail if any `group_by` field is set.

## Options

See the “Shared options” section at the module documentation.

## Examples

    # Returns the number of visits per blog post
    Repo.aggregate(Post, :count, :visits)

    # Returns the average number of visits for the top 10
    query = from Post, limit: 10
    Repo.aggregate(query, :avg, :visits)

Callback implementation for `Ecto.Repo.aggregate/4`.

all(queryable, opts \\ [])

Fetches all entries from the data store matching the given query.

May raise `Ecto.QueryError` if query validation fails.

## Options

- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This overrides the prefix set in the query.

See the “Shared options” section at the module documentation.

## Example

    # Fetch all post titles
    query = from p in Post,
         select: p.title
    MyRepo.all(query)

Callback implementation for `Ecto.Repo.all/2`.

config()

Returns the adapter configuration stored in the `:otp_app` environment.

Dynamic configuration is not reflected on this value.

Callback implementation for `Ecto.Repo.config/0`.

delete(struct, opts \\ [])

Deletes a struct using its primary key.

If the struct has no primary key, `Ecto.NoPrimaryKeyFieldError` will be raised.

It returns `{:ok, struct}` if the struct has been successfully deleted or `{:error, changeset}` if there was a validation or a known constraint error.

## Options

- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This overrides the prefix set in the struct.

See the “Shared options” section at the module documentation.

## Example

    post = MyRepo.get!(Post, 42)
    case MyRepo.delete post do
      {:ok, struct}       -> # Deleted with success
      {:error, changeset} -> # Something went wrong
    end

Callback implementation for `Ecto.Repo.delete/2`.

delete!(struct, opts \\ [])

Same as `delete/2` but returns the struct or raises if the changeset is invalid.

Callback implementation for `Ecto.Repo.delete!/2`.

delete_all(queryable, opts \\ [])

Deletes all entries matching the given query.

It returns a tuple containing the number of entries and any returned result as second element. If the database does not support RETURNING in DELETE statements or no return result was selected, the second element will be `nil`.

## Options

- `:returning` - selects which fields to return. When `true`, returns all fields in the given struct. May be a list of fields, where a struct is still returned but only with the given fields. Or `false`, where nothing is returned (the default). This option is not supported by all databases.
- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This overrides the prefix set in the query.

See the “Shared options” section at the module documentation for remaining options.

## Examples

    MyRepo.delete_all(Post)

    from(p in Post, where: p.id < 10) |> MyRepo.delete_all

Callback implementation for `Ecto.Repo.delete_all/2`.

get(queryable, id, opts \\ [])

Fetches a single struct from the data store where the primary key matches the given id.

Returns `nil` if no result was found. If the struct in the queryable has no or more than one primary key, it will raise an argument error.

## Options

See the “Shared options” section at the module documentation.

## Example

    MyRepo.get(Post, 42)

Callback implementation for `Ecto.Repo.get/3`.

get!(queryable, id, opts \\ [])

Similar to `get/3` but raises `Ecto.NoResultsError` if no record was found.

## Options

See the “Shared options” section at the module documentation.

## Example

    MyRepo.get!(Post, 42)

Callback implementation for `Ecto.Repo.get!/3`.

get_by(queryable, clauses, opts \\ [])

Fetches a single result from the query.

Returns `nil` if no result was found.

## Options

See the “Shared options” section at the module documentation.

## Example

    MyRepo.get_by(Post, title: "My post")

Callback implementation for `Ecto.Repo.get_by/3`.

get_by!(queryable, clauses, opts \\ [])

Similar to `get_by/3` but raises `Ecto.NoResultsError` if no record was found.

## Options

See the “Shared options” section at the module documentation.

## Example

    MyRepo.get_by!(Post, title: "My post")

Callback implementation for `Ecto.Repo.get_by!/3`.

in_transaction?()

Returns true if the current process is inside a transaction.

## Examples

    MyRepo.in_transaction?
    #=> false

    MyRepo.transaction(fn ->
      MyRepo.in_transaction? #=> true
    end)

Callback implementation for `Ecto.Repo.in_transaction?/0`.

init(, opts)

Dynamically loads the repository url from the DATABASE_URL environment variable.

insert(struct, opts \\ [])

Inserts a struct or a changeset.

In case a struct is given, the struct is converted into a changeset with all non-nil fields as part of the changeset.

In case a changeset is given, the changes in the changeset are merged with the struct fields, and all of them are sent to the database.

It returns `{:ok, struct}` if the struct has been successfully inserted or `{:error, changeset}` if there was a validation or a known constraint error.

## Options

- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This overrides the prefix set in the struct.
- `:on_conflict` - It may be one of `:raise` (the default), `:nothing`, `:replace_all`, a keyword list of update instructions or an `Ecto.Query` query for updates. See the “Upserts” section for more information.
- `:conflict_target` - Which columns to verify for conflicts. If none is specified, the conflict target is left up to the database and is usually made of primary keys and/or unique/exclusion constraints.

See the “Shared options” section at the module documentation.

## Examples

A typical example is calling `MyRepo.insert/1` with a struct and acting on the return value:

    case MyRepo.insert %Post{title: "Ecto is great"} do
      {:ok, struct}       -> # Inserted with success
      {:error, changeset} -> # Something went wrong
    end

## Upserts

`insert_all` provides upserts (update or inserts) via the `:on_conflict` option. The `:on_conflict` option supports the following values:

- `:raise` - raises if there is a conflicting primary key or unique index
- `:nothing` - ignores the error in case of conflicts
- `:replace_all` - replace all entries in the database by the one being currently attempted
- a keyword list of update instructions - such as the one given to `c:update_all/3`, for example: `[set: [title: "new title"]]`
- an `Ecto.Query` that will act as an `UPDATE` statement, such as the one given to `c:update_all/3`

Upserts map to “ON CONFLICT” on databases like Postgres and “ON DUPLICATE KEY” on databases such as MySQL.

As an example, imagine `:title` is marked as a unique column in the database:

    # Insert it once
    {:ok, inserted} = MyRepo.insert(%Post{title: "this is unique"})

    # Insert with the same title but do nothing on conflicts.
    # Keep in mind that, although this returns :ok, the returned
    # struct does not reflect the data in the database. For instance,
    # in case of "on_conflict: :nothing", the returned post has no ID.
    {:ok, ignored} = MyRepo.insert(%Post{title: "this is unique"}, on_conflict: :nothing)
    assert ignored.id == nil

    # Now let's insert with the same title but use a query to update
    # a column on conflicts. Although this returns :ok and a struct with
    # the existing ID for successful operations, the other columns may
    # not necessarily reflect the data in the database. In fact, any
    # operation done on `:on_conflict` won't be automatically mapped to
    # the struct.

    # In Postgres (it requires the conflict target for updates):
    on_conflict = [set: [body: "updated"]]
    {:ok, updated} = MyRepo.insert(%Post{title: "this is unique"},
                                   on_conflict: on_conflict, conflict_target: :title)

    # In MySQL (conflict target is not supported):
    on_conflict = [set: [title: "updated"]]
    {:ok, updated} = MyRepo.insert(%Post{id: inserted.id, title: "updated"},
                                   on_conflict: on_conflict)

Callback implementation for `Ecto.Repo.insert/2`.

insert!(struct, opts \\ [])

Same as `insert/2` but returns the struct or raises if the changeset is invalid.

Callback implementation for `Ecto.Repo.insert!/2`.

insert_all(schema_or_source, entries, opts \\ [])

Inserts all entries into the repository.

It expects a schema (`MyApp.User`) or a source (`"users"`) or both (`{"users", MyApp.User}`) as the first argument. The second argument is a list of entries to be inserted, either as keyword lists or as maps.

It returns a tuple containing the number of entries and any returned result as second element. If the database does not support RETURNING in UPDATE statements or no return result was selected, the second element will be `nil`.

When a schema is given, the values given will be properly dumped before being sent to the database. If the schema contains an autogenerated ID field, it will be handled either at the adapter or the storage layer. However any other autogenerated value, like timestamps, won’t be autogenerated when using `c:insert_all/3`. This is by design as this function aims to be a more direct way to insert data into the database without the conveniences of `c:insert/2`. This is also consistent with `c:update_all/3` that does not handle timestamps as well.

If a source is given, without a schema, the given fields are passed as is to the adapter.

## Options

- `:returning` - selects which fields to return. When `true`, returns all fields in the given struct. May be a list of fields, where a struct is still returned but only with the given fields. Or `false`, where nothing is returned (the default). This option is not supported by all databases.
- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL).
- `:on_conflict` - It may be one of `:raise` (the default), `:nothing`, `:replace_all`, a keyword list of update instructions or an `Ecto.Query` query for updates. See the “Upserts” section for more information.
- `:conflict_target` - Which columns to verify for conflicts. If none is specified, the conflict target is left up to the database and is usually made of primary keys and/or unique/exclusion constraints.

See the “Shared options” section at the module documentation for remaining options.

## Examples

    MyRepo.insert_all(Post, [[title: "My first post"], [title: "My second post"]])
    MyRepo.insert_all(Post, [%{title: "My first post"}, %{title: "My second post"}])

## Upserts

`insert_all` provides upserts (update or inserts) via the `:on_conflict` option. The `:on_conflict` option supports the following values:

- `:raise` - raises if there is a conflicting primary key or unique index
- `:nothing` - ignores the error in case of conflicts
- `:replace_all` - replace all entries in the database by the one being currently attempted
- a keyword list of update instructions - such as the one given to `c:update_all/3`, for example: `[set: [title: "new title"]]`
- an `Ecto.Query` that will act as an `UPDATE` statement, such as the one given to `c:update_all/3`

Upserts map to “ON CONFLICT” on databases like Postgres and “ON DUPLICATE KEY” on databases such as MySQL.

## Return values

By default, both Postgres and MySQL return the amount of entries inserted on `insert_all`. However, when the `:on_conflict` option is specified, Postgres will only return a row if it was affected while MySQL returns at least the number of entries attempted.

For example, if `:on_conflict` is set to `:nothing`, Postgres will return 0 if no new entry was added while MySQL will still return the amount of entries attempted to be inserted, even if no entry was added. Even worse, if `:on_conflict` is query, MySQL will return the number of attempted entries plus the number of entries modified by the UPDATE query.

Callback implementation for `Ecto.Repo.insert_all/3`.

insert_or_update(changeset, opts \\ [])

Inserts or updates a changeset depending on whether the struct is persisted or not.

The distinction whether to insert or update will be made on the `Ecto.Schema.Metadata` field `:state`. The `:state` is automatically set by Ecto when loading or building a schema.

Please note that for this to work, you will have to load existing structs from the database. So even if the struct exists, this won’t work:

    struct = %Post{id: 'existing_id', ...}
    MyRepo.insert_or_update changeset
    # => {:error, "id already exists"}

## Options

- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This overrides the prefix set in the struct.

See the “Shared options” section at the module documentation.

## Example

    result =
      case MyRepo.get(Post, id) do
        nil  -> %Post{id: id} # Post not found, we build one
        post -> post          # Post exists, let's use it
      end
      |> Post.changeset(changes)
      |> MyRepo.insert_or_update

    case result do
      {:ok, struct}       -> # Inserted or updated with success
      {:error, changeset} -> # Something went wrong
    end

Callback implementation for `Ecto.Repo.insert_or_update/2`.

insert_or_update!(changeset, opts \\ [])

Same as `insert_or_update/2` but returns the struct or raises if the changeset is invalid.

Callback implementation for `Ecto.Repo.insert_or_update!/2`.

load(schema_or_types, data)

Loads `data` into a struct or a map.

The first argument can be a schema, or a map (of types) and determines the return value: a struct or a map, respectively.

The second argument `data` specifies fields and values that are to be loaded. It can be a map, a keyword list, or a `{fields, values}` tuple. Fields can be atoms or strings.

Fields that are not present in the schema (or `types` map) are ignored. If any of the values has invalid type, an error is raised.

## Examples

    iex> MyRepo.load(User, %{name: "Alice", age: 25})
    %User{name: "Alice", age: 25}

    iex> MyRepo.load(User, [name: "Alice", age: 25])
    %User{name: "Alice", age: 25}

`data` can also take form of `{fields, values}`:

    iex> MyRepo.load(User, {[:name, :age], ["Alice", 25]})
    %User{name: "Alice", age: 25, ...}

The first argument can also be a `types` map:

    iex> types = %{name: :string, age: :integer}
    iex> MyRepo.load(types, %{name: "Alice", age: 25})
    %{name: "Alice", age: 25}

This function is especially useful when parsing raw query results:

    iex> result = Ecto.Adapters.SQL.query!(MyRepo, "SELECT * FROM users", [])
    iex> Enum.map(result.rows, &MyRepo.load(User, {result.columns, &1}))
    [%User{...}, ...]

Callback implementation for `Ecto.Repo.load/2`.

one(queryable, opts \\ [])

Fetches a single result from the query.

Returns `nil` if no result was found. Raises if more than one entry.

## Options

See the “Shared options” section at the module documentation.

Callback implementation for `Ecto.Repo.one/2`.

one!(queryable, opts \\ [])

Similar to `one/2` but raises `Ecto.NoResultsError` if no record was found.

Raises if more than one entry.

## Options

See the “Shared options” section at the module documentation.

Callback implementation for `Ecto.Repo.one!/2`.

preload(struct_or_structs, preloads, opts \\ [])

Preloads all associations on the given struct or structs.

This is similar to `Ecto.Query.preload/3` except it allows you to preload structs after they have been fetched from the database.

In case the association was already loaded, preload won’t attempt to reload it.

## Options

Besides the “Shared options” section at the module documentation, it accepts:

- `:force` - By default, Ecto won’t preload associations that are already loaded. By setting this option to true, any existing association will be discarded and reloaded.
- `:in_parallel` - If the preloads must be done in parallel. It can only be performed when we have more than one preload and the repository is not in a transaction. Defaults to `true`.
- `:prefix` - the prefix to fetch preloads from. By default, queries will use the same prefix as the one in the given collection. This option allows the prefix to be changed.

## Examples

    posts = Repo.preload posts, :comments
    posts = Repo.preload posts, comments: :permalinks
    posts = Repo.preload posts, comments: from(c in Comment, order_by: c.published_at)

Callback implementation for `Ecto.Repo.preload/3`.

query(sql, params \\ [], opts \\ [])

A convenience function for SQL-based repositories that executes the given query.

See `Ecto.Adapters.SQL.query/3` for more information.

query!(sql, params \\ [], opts \\ [])

A convenience function for SQL-based repositories that executes the given query.

See `Ecto.Adapters.SQL.query/3` for more information.

rollback(value)

    rollback(term) :: no_return

Rolls back the current transaction.

The transaction will return the value given as `{:error, value}`.

Callback implementation for `Ecto.Repo.rollback/1`.

start_link(opts \\ [])

Starts any connection pooling or supervision and return `{:ok, pid}` or just `:ok` if nothing needs to be done.

Returns `{:error, {:already_started, pid}}` if the repo is already started or `{:error, term}` in case anything else goes wrong.

## Options

See the configuration in the moduledoc for options shared between adapters, for adapter-specific configuration see the adapter’s documentation.

Callback implementation for `Ecto.Repo.start_link/1`.

stop(pid, timeout \\ 5000)

Shuts down the repository represented by the given pid.

Callback implementation for `Ecto.Repo.stop/2`.

stream(queryable, opts \\ [])

Returns a lazy enumerable that emits all entries from the data store matching the given query. SQL adapters, such as Postgres and MySQL, can only enumerate a stream inside a transaction.

May raise `Ecto.QueryError` if query validation fails.

## Options

- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This overrides the prefix set in the query

- `:max_rows` - The number of rows to load from the database as we stream. It is supported at least by Postgres and MySQL and defaults to 500.

See the “Shared options” section at the module documentation.

## Example

    # Fetch all post titles
    query = from p in Post,
         select: p.title
    stream = MyRepo.stream(query)
    MyRepo.transaction(fn() ->
      Enum.to_list(stream)
    end)

Callback implementation for `Ecto.Repo.stream/2`.

transaction(fun_or_multi, opts \\ [])

Runs the given function or `Ecto.Multi` inside a transaction.

## Use with function

If an unhandled error occurs the transaction will be rolled back and the error will bubble up from the transaction function. If no error occurred the transaction will be committed when the function returns. A transaction can be explicitly rolled back by calling `rollback/1`, this will immediately leave the function and return the value given to `rollback` as `{:error, value}`.

A successful transaction returns the value returned by the function wrapped in a tuple as `{:ok, value}`.

If `transaction/2` is called inside another transaction, the function is simply executed, without wrapping the new transaction call in any way. If there is an error in the inner transaction and the error is rescued, or the inner transaction is rolled back, the whole outer transaction is marked as tainted, guaranteeing nothing will be committed.

## Use with Ecto.Multi

Besides functions transaction can be used with an Ecto.Multi struct. Transaction will be started, all operations applied and in case of success committed returning `{:ok, changes}`. In case of any errors the transaction will be rolled back and `{:error, failed_operation, failed_value, changes_so_far}` will be returned.

You can read more about using transactions with `Ecto.Multi` as well as see some examples in the `Ecto.Multi` documentation.

## Options

See the “Shared options” section at the module documentation.

## Examples

    MyRepo.transaction(fn ->
      MyRepo.update!(%{alice | balance: alice.balance - 10})
      MyRepo.update!(%{bob | balance: bob.balance + 10})
    end)

    # Roll back a transaction explicitly
    MyRepo.transaction(fn ->
      p = MyRepo.insert!(%Post{})
      if not Editor.post_allowed?(p) do
        MyRepo.rollback(:posting_not_allowed)
      end
    end)

    # With Ecto.Multi
    Ecto.Multi.new
    |> Ecto.Multi.insert(:post, %Post{})
    |> MyRepo.transaction

Callback implementation for `Ecto.Repo.transaction/2`.

update(struct, opts \\ [])

Updates a changeset using its primary key.

A changeset is required as it is the only mechanism for tracking dirty changes. Only the fields present in the `changes` part of the changeset are sent to the database. Any other, in-memory changes done to the schema are ignored.

If the struct has no primary key, `Ecto.NoPrimaryKeyFieldError` will be raised.

It returns `{:ok, struct}` if the struct has been successfully updated or `{:error, changeset}` if there was a validation or a known constraint error.

## Options

Besides the “Shared options” section at the module documentation, it accepts:

- `:force` - By default, if there are no changes in the changeset, `update!/2` is a no-op. By setting this option to true, update callbacks will always be executed, even if there are no changes (including timestamps).
- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This overrides the prefix set in the struct.

## Example

    post = MyRepo.get!(Post, 42)
    post = Ecto.Changeset.change post, title: "New title"
    case MyRepo.update post do
      {:ok, struct}       -> # Updated with success
      {:error, changeset} -> # Something went wrong
    end

Callback implementation for `Ecto.Repo.update/2`.

update!(struct, opts \\ [])

Same as `update/2` but returns the struct or raises if the changeset is invalid.

Callback implementation for `Ecto.Repo.update!/2`.

update_all(queryable, updates, opts \\ [])

Updates all entries matching the given query with the given values.

It returns a tuple containing the number of entries and any returned result as second element. If the database does not support RETURNING in UPDATE statements or no return result was selected, the second element will be `nil`.

Keep in mind this `update_all` will not update autogenerated fields like the `updated_at` columns.

See `Ecto.Query.update/3` for update operations that can be performed on fields.

## Options

- `:returning` - selects which fields to return. When `true`, returns all fields in the given struct. May be a list of fields, where a struct is still returned but only with the given fields. Or `false`, where nothing is returned (the default). This option is not supported by all databases.
- `:prefix` - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This overrides the prefix set in the query.

See the “Shared options” section at the module documentation for remaining options.

## Examples

    MyRepo.update_all(Post, set: [title: "New title"])

    MyRepo.update_all(Post, inc: [visits: 1])

    from(p in Post, where: p.id < 10)
    |> MyRepo.update_all(set: [title: "New title"])

    from(p in Post, where: p.id < 10, update: [set: [title: "New title"]])
    |> MyRepo.update_all([])

    from(p in Post, where: p.id < 10, update: [set: [title: fragment("?", new_title)]])
    |> MyRepo.update_all([])

Callback implementation for `Ecto.Repo.update_all/3`.