Ecto v2.2.8 Ecto.Repo behaviour View Source

Defines a repository.

A repository maps to an underlying data store, controlled by the adapter. For example, Ecto ships with a Postgres adapter that stores data into a PostgreSQL database.

When used, the repository expects the :otp_app as option. The :otp_app should point to an OTP application that has the repository configuration. For example, the repository:

defmodule Repo do
  use Ecto.Repo, otp_app: :my_app
end

Could be configured with:

config :my_app, Repo,
  adapter: Ecto.Adapters.Postgres,
  database: "ecto_simple",
  username: "postgres",
  password: "postgres",
  hostname: "localhost"

Most of the configuration that goes into the config is specific to the adapter, so check Ecto.Adapters.Postgres documentation for more information. However, some configuration is shared across all adapters, they are:

  • :adapter - a compile-time option that specifies the adapter itself. As a compile-time option, it may also be given as an option to use Ecto.Repo.

  • :name- The name of the Repo supervisor process

  • :priv - the directory where to keep repository data, like migrations, schema and more. Defaults to “priv/YOUR_REPO”. It must always point to a subdirectory inside the priv directory.

  • :url - an URL that specifies storage information. Read below for more information

  • :loggers - a list of {mod, fun, args} tuples that are invoked by adapters for logging queries and other events. The given module and function will be called with a log entry (see Ecto.LogEntry) and the given arguments. The invoked function must return the Ecto.LogEntry as result. The default value is: [{Ecto.LogEntry, :log, []}], which will call Ecto.LogEntry.log/1 that will use Elixir’s Logger in :debug mode. You may pass any desired mod-fun-args triplet or [{Ecto.LogEntry, :log, [:info]}] if you want to keep the current behaviour but use another log level. This option is processed at compile-time and may also be given as an option to use Ecto.Repo.

URLs

Repositories by default support URLs. For example, the configuration above could be rewritten to:

config :my_app, Repo,
  url: "ecto://postgres:postgres@localhost/ecto_simple"

The schema can be of any value. The path represents the database name while options are simply merged in.

URL can include query parameters to override shared and adapter-specific options ssl, timeout, pool_timeout, pool_size:

config :my_app, Repo,

  url: "ecto://postgres:postgres@localhost/ecto_simple?ssl=true&pool_size=10"

In case the URL needs to be dynamically configured, for example by reading a system environment variable, such can be done via the init/2 repository callback:

def init(_type, config) do
  {:ok, Keyword.put(config, :url, System.get_env("DATABASE_URL"))}
end

Shared options

Almost all of the repository operations below accept the following options:

  • :timeout - The time in milliseconds to wait for the query call to finish, :infinity will wait indefinitely (default: 15000);
  • :pool_timeout - The time in milliseconds to wait for calls to the pool to finish, :infinity will wait indefinitely (default: 5000);
  • :log - When false, does not log the query

Such cases will be explicitly documented as well as any extra option.

Link to this section Summary

Callbacks

Returns the adapter tied to the repository

A callback invoked by adapters that logs the given action

Calculate the given aggregate over the given field

Fetches all entries from the data store matching the given query

Returns the adapter configuration stored in the :otp_app environment

Deletes a struct using its primary key

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

Deletes all entries matching the given query

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

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

Fetches a single result from the query

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

Returns true if the current process is inside a transaction

A callback executed when the repo starts or when configuration is read

Inserts a struct defined via Ecto.Schema or a changeset

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

Inserts all entries into the repository

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

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

Loads data into a struct or a map

Fetches a single result from the query

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

Preloads all associations on the given struct or structs

Rolls back the current transaction

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

Shuts down the repository represented by the given pid

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

Runs the given function or Ecto.Multi inside a transaction

Updates a changeset using its primary key

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

Updates all entries matching the given query with the given values

Link to this section Types

Link to this section Callbacks

Returns the adapter tied to the repository.

A callback invoked by adapters that logs the given action.

See Ecto.LogEntry for more information and Ecto.Repo module documentation on setting up your own loggers.

Link to this callback aggregate(queryable, aggregate, field, opts) View Source
aggregate(queryable :: Ecto.Queryable.t(), aggregate :: :avg | :count | :max | :min | :sum, field :: atom(), opts :: Keyword.t()) ::
  term() |
  nil

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)
Link to this callback all(queryable, opts) View Source
all(queryable :: Ecto.Query.t(), opts :: Keyword.t()) ::
  [Ecto.Schema.t()] |
  no_return()

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)

Returns the adapter configuration stored in the :otp_app environment.

If the init/2 callback is implemented in the repository, it will be invoked with the first argument set to :dry_run.

Link to this callback delete(struct_or_changeset, opts) View Source
delete(struct_or_changeset :: Ecto.Schema.t() | Ecto.Changeset.t(), opts :: Keyword.t()) ::
  {:ok, Ecto.Schema.t()} |
  {:error, Ecto.Changeset.t()}

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
Link to this callback delete!(struct_or_changeset, opts) View Source
delete!(struct_or_changeset :: Ecto.Schema.t() | Ecto.Changeset.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  no_return()

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

Link to this callback delete_all(queryable, opts) View Source
delete_all(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) ::
  {integer(), nil | [term()]} |
  no_return()

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
Link to this callback get(queryable, id, opts) View Source
get(queryable :: Ecto.Queryable.t(), id :: term(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  nil |
  no_return()

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)
Link to this callback get!(queryable, id, opts) View Source
get!(queryable :: Ecto.Queryable.t(), id :: term(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  nil |
  no_return()

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)
Link to this callback get_by(queryable, clauses, opts) View Source
get_by(queryable :: Ecto.Queryable.t(), clauses :: Keyword.t() | map(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  nil |
  no_return()

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")
Link to this callback get_by!(queryable, clauses, opts) View Source
get_by!(queryable :: Ecto.Queryable.t(), clauses :: Keyword.t() | map(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  nil |
  no_return()

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")
Link to this callback in_transaction?() View Source (optional)
in_transaction?() :: boolean()

Returns true if the current process is inside a transaction.

Examples

MyRepo.in_transaction?
#=> false

MyRepo.transaction(fn ->
  MyRepo.in_transaction? #=> true
end)
Link to this callback init(arg0, config) View Source (optional)
init(:supervisor | :dry_run, config :: Keyword.t()) ::
  {:ok, Keyword.t()} |
  :ignore

A callback executed when the repo starts or when configuration is read.

The first argument is the context the callback is being invoked. If it is called because the Repo supervisor is starting, it will be :supervisor. It will be :dry_run if it is called for reading configuration without actually starting a process.

The second argument is the repository configuration as stored in the application environment. It must return {:ok, keyword} with the updated list of configuration or :ignore (only in the :supervisor case).

Link to this callback insert(struct_or_changeset, opts) View Source
insert(struct_or_changeset :: Ecto.Schema.t() | Ecto.Changeset.t(), opts :: Keyword.t()) ::
  {:ok, Ecto.Schema.t()} |
  {:error, Ecto.Changeset.t()}

Inserts a struct defined via Ecto.Schema 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

  • :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. In any case, it will include fields with read_after_writes set to true. 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 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. May also be {:constraint, constraint_name_as_atom} in databases that support the “ON CONSTRAINT” expression.

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/2 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 values on the existing row with the values in the excluded row (the record given in the function parameters)
  • a keyword list of update instructions - such as the one given to 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 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:

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

Now we can insert with the same title but do nothing on conflicts:

{:ok, ignored} = MyRepo.insert(%Post{title: "this is unique"}, on_conflict: :nothing)
assert ignored.id == nil

Because we used on_conflict: :nothing, instead of getting an error, we got {:ok, struct}. However the returned struct does not reflect the data in the database. One possible mechanism to detect if an insert or nothing happened in case of on_conflict: :nothing is by checking the id field. id will be nil if the field is autogenerated by the database and no insert happened.

For actual upserts, where an insert or update may happen, the situation is slightly more complex, as the database does not actually inform us if an insert or update happened. Let’s insert a post with the same title but use a query to update the body column in case of conflicts:

# 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)

In the examples above, even though it returned :ok, we do not know if we inserted new data or if we updated only the :on_conflict fields. In case an update happened, the data in the struct most likely does not match the data in the database. For example, autogenerated fields such as inserted_at will point to now rather than the time the struct was actually inserted.

If you need to guarantee the data in the returned struct mirrors the database, you have three options:

  • Use on_conflict: :replace_all, although that will replace all fields in the database with current ones:

    MyRepo.insert(%Post{title: "this is unique"},
                  on_conflict: :replace_all, conflict_target: :title)
  • Specify read_after_writes: true in your schema for choosing fields that are read from the database after every operation. Or pass returning: true to insert to read all fields back:

    MyRepo.insert(%Post{title: "this is unique"}, returning: true,
                  on_conflict: on_conflict, conflict_target: :title)
  • Alternatively, read the data again from the database in a separate query. This option requires the primary key to be generated by the database:

    {:ok, updated} = MyRepo.insert(%Post{title: "this is unique"}, on_conflict: on_conflict)
    Repo.get(Post, updated.id)
Link to this callback insert!(struct_or_changeset, opts) View Source
insert!(struct_or_changeset :: Ecto.Schema.t() | Ecto.Changeset.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  no_return()

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

Link to this callback insert_all(schema_or_source, entries, opts) View Source
insert_all(schema_or_source :: binary() | {binary(), Ecto.Schema.t()} | Ecto.Schema.t(), entries :: [map() | Keyword.t()], opts :: Keyword.t()) ::
  {integer(), nil | [term()]} |
  no_return()

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 INSERT 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 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 insert/2. This is also consistent with update_all/3 that does not handle timestamps as well.

It is also not possible to use insert_all to insert across multiple tables, therefore associations are not supported.

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. May also be {:constraint, constraint_name_as_atom} in databases that support the “ON CONSTRAINT” expression.

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/3 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 values on the existing row with the values in the excluded row (the corresponding record given in the function parameters)
  • a keyword list of update instructions - such as the one given to 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 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/3. 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.

Link to this callback insert_or_update(changeset, opts) View Source
insert_or_update(changeset :: Ecto.Changeset.t(), opts :: Keyword.t()) ::
  {:ok, Ecto.Schema.t()} |
  {:error, Ecto.Changeset.t()}

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, changeset} # 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
Link to this callback insert_or_update!(changeset, opts) View Source
insert_or_update!(changeset :: Ecto.Changeset.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  no_return()

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

Link to this callback load(arg0, arg1) View Source
load(Ecto.Schema.t() | map(), map() | Keyword.t() | {list(), list()}) ::
  Ecto.Schema.t() |
  map()

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{...}, ...]
Link to this callback one(queryable, opts) View Source
one(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  nil |
  no_return()

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.

Link to this callback one!(queryable, opts) View Source
one!(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  no_return()

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.

Link to this callback preload(structs_or_struct_or_nil, preloads, opts) View Source
preload(structs_or_struct_or_nil, preloads :: term(), opts :: Keyword.t()) :: structs_or_struct_or_nil when structs_or_struct_or_nil: [Ecto.Schema.t()] | Ecto.Schema.t() | nil

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

# Use a single atom to preload an association
posts = Repo.preload posts, :comments

# Use a list of atoms to preload multiple associations
posts = Repo.preload posts, [:comments, :authors]

# Use a keyword list to preload nested associations as well
posts = Repo.preload posts, [comments: [:replies, :likes], authors: []]

# Use a keyword list to customize how associations are queried
posts = Repo.preload posts, [comments: from(c in Comment, order_by: c.published_at)]

# Use a two-element tuple for a custom query and nested association definition
query = from c in Comment, order_by: c.published_at
posts = Repo.preload posts, [comments: {query, [:replies, :likes]}]

Note: The query given to preload may also preload its own associations.

Link to this callback rollback(value) View Source (optional)
rollback(value :: any()) :: no_return()

Rolls back the current transaction.

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

Link to this callback start_link(opts) View Source
start_link(opts :: Keyword.t()) ::
  {:ok, pid()} |
  {:error, {:already_started, pid()}} |
  {:error, term()}

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.

Link to this callback stop(pid, timeout) View Source
stop(pid(), timeout()) :: :ok

Shuts down the repository represented by the given pid.

Link to this callback stream(queryable, opts) View Source
stream(queryable :: Ecto.Query.t(), opts :: Keyword.t()) :: Enum.t()

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)
Link to this callback transaction(fun_or_multi, opts) View Source (optional)
transaction(fun_or_multi :: (... -> any()) | Ecto.Multi.t(), opts :: Keyword.t()) ::
  {:ok, any()} |
  {:error, any()} |
  {:error, atom(), any(), %{optional(atom()) => any()}}

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

import Ecto.Changeset, only: [change: 2]

MyRepo.transaction(fn ->
  MyRepo.update!(change(alice, balance: alice.balance - 10))
  MyRepo.update!(change(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
Link to this callback update(changeset, opts) View Source
update(changeset :: Ecto.Changeset.t(), opts :: Keyword.t()) ::
  {:ok, Ecto.Schema.t()} |
  {:error, Ecto.Changeset.t()}

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
Link to this callback update!(changeset, opts) View Source
update!(changeset :: Ecto.Changeset.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() |
  no_return()

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

Link to this callback update_all(queryable, updates, opts) View Source
update_all(queryable :: Ecto.Queryable.t(), updates :: Keyword.t(), opts :: Keyword.t()) ::
  {integer(), nil | [term()]} |
  no_return()

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: ^new_title]])
|> MyRepo.update_all([])

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