View Source Ecto.Repo behaviour (Ecto v3.12.4)

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 and :adapter 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,
    adapter: Ecto.Adapters.Postgres
end

Could be configured with:

config :my_app, Repo,
  database: "ecto_simple",
  username: "postgres",
  password: "postgres",
  hostname: "localhost"

Most of the configuration that goes into the config is specific to the adapter. For this particular example, you can check Ecto.Adapters.Postgres for more information. In spite of this, the following configuration values are common across all adapters:

  • :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

  • :log - the log level used when logging the query with Elixir's Logger. Can be any of Logger.level/0 values or false. If false, disables logging for that repository. Defaults to :debug

  • :pool_size - the size of the pool used by the connection module. Defaults to 10

  • :pool_count - the number of pools to run concurrently, increase this option when the pool itself may be under contention. When running multiple pools, queries are randomly routed to different pools, without taking into account how many connections are available in each. So in some circumstances, you may be routed to a fully busy pool while others have connections available. The overall number of connections used will be pool_size * pool_count. Defaults to 1

  • :telemetry_prefix - we recommend adapters to publish events using the Telemetry library. By default, the telemetry prefix is based on the module name, so if your module is called MyApp.Repo, the prefix will be [:my_app, :repo]. See the "Telemetry Events" section to see which events we recommend adapters to publish. Note that if you have multiple databases, you should keep the :telemetry_prefix consistent for each repo and use the :repo property in the event metadata for distinguishing between repos.

  • :stacktrace- when true, publishes the stacktrace in telemetry events and allows more advanced logging.

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 and the path represents the database name. The URL will be used generate the relevant Repo configuration values, such as :database, :username, :password, :hostname and :port. These values take precedence over those already specified in the Repo's configuration.

URL can include query parameters to override shared and adapter-specific options, like ssl, timeout and pool_size. The following example shows how to pass these configuration values:

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

Shared options

Almost all of the repository functions outlined in this module accept the following options:

  • :timeout - The time in milliseconds (as an integer) to wait for the query call to finish. :infinity will wait indefinitely (default: 15_000)
  • :log - Can be any of the Logger.level/0 values or false. If false, logging is disabled. Defaults to the configured Repo logger level
  • :telemetry_event - The telemetry event name to dispatch the event under. See the next section for more information
  • :telemetry_options - Extra options to attach to telemetry event name. See the next section for more information

Adapter-Specific Errors

Many of the functions in this module may raise adapter-specific errors, such as PostgrexError. This can happen, for example, when the underlying database cannot execute the specified query.

Telemetry events

There are two types of telemetry events. The ones emitted by Ecto and the ones that are adapter specific.

Ecto telemetry events

The following events are emitted by all Ecto repositories:

  • [:ecto, :repo, :init] - it is invoked whenever a repository starts. The measurement is a single system_time entry in native unit. The metadata is the :repo and all initialization options under :opts.

Adapter-specific events

We recommend adapters to publish certain Telemetry events listed below. Those events will use the :telemetry_prefix outlined above which defaults to [:my_app, :repo].

For instance, to receive all query events published by a repository called MyApp.Repo, one would define a module:

defmodule MyApp.Telemetry do
  def handle_event([:my_app, :repo, :query], measurements, metadata, config) do
    IO.inspect binding()
  end
end

Then, in the Application.start/2 callback, attach the handler to this event using a unique handler id:

:ok = :telemetry.attach("my-app-handler-id", [:my_app, :repo, :query], &MyApp.Telemetry.handle_event/4, %{})

For details, see the telemetry documentation.

Below we list all events developers should expect from Ecto. All examples below consider a repository named MyApp.Repo:

[:my_app, :repo, :query]

This event should be invoked on every query sent to the adapter, including queries that are related to the transaction management.

The :measurements map may include the following, all given in the :native time unit:

  • :idle_time - the time the connection spent waiting before being checked out for the query
  • :queue_time - the time spent waiting to check out a database connection
  • :query_time - the time spent executing the query
  • :decode_time - the time spent decoding the data received from the database
  • :total_time - the sum of (queue_time, query_time, and decode_time)️

All measurements are given in the :native time unit. You can read more about it in the docs for System.convert_time_unit/3.

A telemetry :metadata map including the following fields. Each database adapter may emit different information here. For Ecto.SQL databases, it will look like this:

  • :type - the type of the Ecto query. For example, for Ecto.SQL databases, it would be :ecto_sql_query
  • :repo - the Ecto repository
  • :result - the query result
  • :params - the dumped query parameters (formatted for database drivers like Postgrex)
  • :cast_params - the casted query parameters (normalized before dumping)
  • :query - the query sent to the database as a string
  • :source - the source the query was made on (may be nil)
  • :stacktrace - the stacktrace information, if enabled, or nil
  • :options - extra options given to the repo operation under :telemetry_options

Read-only repositories

You can mark a repository as read-only by passing the :read_only flag on use:

use Ecto.Repo, otp_app: ..., adapter: ..., read_only: true

By passing the :read_only option, none of the functions that perform write operations, such as insert/2, insert_all/3, update_all/3, and friends will be defined.

Summary

Query API

Calculate the given aggregate.

Calculate the given aggregate over the given field.

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

Deletes all entries matching the given query.

Checks if there exists an entry that matches 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.

Fetches a single result from the query.

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

Returns a lazy enumerable that emits all entries from the data store matching the given query.

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

Schema API

Deletes a struct using its primary key.

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

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 schema or a map.

Preloads all associations on the given struct or structs.

Reloads a given schema or schema list from the database.

Similar to reload/2, but raises when something is not found.

Updates a changeset using its primary key.

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

Transaction API

Returns true if a connection has been checked out.

Checks out a connection for the duration of the function.

Returns true if the current process is inside a transaction.

Rolls back the current transaction.

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

Process API

Returns the atom name or pid of the current repository.

Sets the dynamic repository to be used in further interactions.

Starts the Repo supervision tree.

Shuts down the repository.

Config API

Returns the adapter tied to the repository.

Returns the adapter configuration stored in the :otp_app environment.

User callbacks

A user customizable callback invoked to retrieve default options for operations.

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

A user customizable callback invoked for query-based operations.

Functions

Returns all running Ecto repositories.

Query API

Link to this callback

aggregate(queryable, aggregate, opts)

View Source (optional)
@callback aggregate(
  queryable :: Ecto.Queryable.t(),
  aggregate :: :count,
  opts :: Keyword.t()
) :: term() | nil

Calculate the given aggregate.

If the query has a limit, offset, distinct or combination 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

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Examples

# Returns the number of blog posts
Repo.aggregate(Post, :count)

# Returns the number of blog posts in the "private" schema path
# (in Postgres) or database (in MySQL)
Repo.aggregate(Post, :count, prefix: "private")
Link to this callback

aggregate(queryable, aggregate, field, opts)

View Source (optional)
@callback 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.

See aggregate/3 for general considerations and options.

Examples

# Returns the sum of the number of visits for every blog post
Repo.aggregate(Post, :sum, :visits)

# Returns the sum of the number of visits for every blog post in the
# "private" schema path (in Postgres) or database (in MySQL)
Repo.aggregate(Post, :sum, :visits, prefix: "private")

# Returns the average number of visits for the first 10 blog posts
query = from Post, limit: 10
Repo.aggregate(query, :avg, :visits)
Link to this callback

all(queryable, opts)

View Source (optional)
@callback all(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) :: [
  Ecto.Schema.t() | term()
]

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 will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Example

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

delete_all(queryable, opts)

View Source (optional)
@callback delete_all(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) ::
  {non_neg_integer(), nil | [term()]}

Deletes all entries matching the given query.

It returns a tuple containing the number of entries and any returned result as second element. The second element is nil by default unless a select is supplied in the delete query. Note, however, not all databases support returning data from DELETEs.

Options

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

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()

# With returning results, if supported by the database.
{_count, posts} = from(p in Post, where: p.id < 10, select: p) |> MyRepo.delete_all()
Link to this callback

exists?(queryable, opts)

View Source (optional)
@callback exists?(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) :: boolean()

Checks if there exists an entry that matches the given query.

Returns a boolean.

Options

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Examples

# checks if any posts exist
Repo.exists?(Post)

# checks if any posts exist in the "private" schema path (in Postgres) or
# database (in MySQL)
Repo.exists?(Post, prefix: "private")

# checks if any post with a like count greater than 10 exists
query = from p in Post, where: p.like_count > 10
Repo.exists?(query)
Link to this callback

get(queryable, id, opts)

View Source (optional)
@callback get(queryable :: Ecto.Queryable.t(), id :: term(), opts :: Keyword.t()) ::
  Ecto.Schema.t() | term() | nil

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

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Example

MyRepo.get(Post, 42)

MyRepo.get(Post, 42, prefix: "public")
Link to this callback

get!(queryable, id, opts)

View Source (optional)
@callback get!(queryable :: Ecto.Queryable.t(), id :: term(), opts :: Keyword.t()) ::
  Ecto.Schema.t() | term()

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

Options

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Example

MyRepo.get!(Post, 42)

MyRepo.get!(Post, 42, prefix: "public")
Link to this callback

get_by(queryable, clauses, opts)

View Source (optional)
@callback get_by(
  queryable :: Ecto.Queryable.t(),
  clauses :: Keyword.t() | map(),
  opts :: Keyword.t()
) :: Ecto.Schema.t() | term() | nil

Fetches a single result from the query.

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

Options

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Example

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

MyRepo.get_by(Post, [title: "My post"], prefix: "public")
Link to this callback

get_by!(queryable, clauses, opts)

View Source (optional)
@callback get_by!(
  queryable :: Ecto.Queryable.t(),
  clauses :: Keyword.t() | map(),
  opts :: Keyword.t()
) :: Ecto.Schema.t() | term()

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

Raises if more than one entry.

Options

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Example

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

MyRepo.get_by!(Post, [title: "My post"], prefix: "public")
Link to this callback

one(queryable, opts)

View Source (optional)
@callback one(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() | term() | nil

Fetches a single result from the query.

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

Options

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Examples

Repo.one(from p in Post, join: c in assoc(p, :comments), where: p.id == ^post_id)

query = from p in Post, join: c in assoc(p, :comments), where: p.id == ^post_id
Repo.one(query, prefix: "private")
Link to this callback

one!(queryable, opts)

View Source (optional)
@callback one!(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() | term()

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

Raises if more than one entry.

Options

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

See the "Shared options" section at the module documentation for more options.

Link to this callback

stream(queryable, opts)

View Source (optional)
@callback stream(queryable :: Ecto.Queryable.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 will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

  • :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 for more options.

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

update_all(queryable, updates, opts)

View Source (optional)
@callback update_all(
  queryable :: Ecto.Queryable.t(),
  updates :: Keyword.t(),
  opts :: Keyword.t()
) :: {non_neg_integer(), nil | [term()]}

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. The second element is nil by default unless a select is supplied in the update query. Note, however, not all databases support returning data from UPDATEs.

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

  • :prefix - The prefix to run the query on (such as the schema path in Postgres or the database in MySQL). This will be applied to all from and joins in the query that did not have a prefix previously given either via the :prefix option on join/from or via @schema_prefix in the schema. For more information see the "Query Prefix" section of the Ecto.Query documentation.

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, select: p.visits)
|> 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([])

from(p in Post, where: p.id < 10, update: [set: [visits: p.visits * 1000]])
|> MyRepo.update_all([])

Schema API

Link to this callback

delete(struct_or_changeset, opts)

View Source (optional)
@callback 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. If the struct has been removed prior to the call, Ecto.StaleEntryError will be raised. If more than one database operation is required, they're automatically wrapped in a transaction.

It returns {:ok, struct} if the struct has been successfully deleted or {:error, changeset} if there was a validation or a known constraint error. By default, constraint errors will raise the Ecto.ConstraintError exception, unless a changeset is given as the first argument with the relevant constraints declared in it (see Ecto.Changeset).

Options

  • :returning - selects which fields to return. It accepts a list of fields to be returned from the database. When true, returns all fields, including those marked as load_in_query: false. When false, no extra fields are returned. It will always include all fields in read_after_writes. Be aware that the fields returned from the database overwrite what was supplied by the user. Any field not returned by the database will be present with the original value supplied by the user. Not all databases support this option.

  • :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 and any @schema_prefix set in the schema.

  • :stale_error_field - The field where stale errors will be added in the returning changeset. This option can be used to avoid raising Ecto.StaleEntryError.

  • :stale_error_message - The message to add to the configured :stale_error_field when stale errors happen, defaults to "is stale".

  • :allow_stale - Doesn't error if delete is stale. Defaults to false. This may happen if the struct has been deleted from the database before this deletion or if there is a rule or a trigger on the database that rejects the delete operation.

See the "Shared options" section at the module documentation for more options.

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 (optional)
@callback delete!(
  struct_or_changeset :: Ecto.Schema.t() | Ecto.Changeset.t(),
  opts :: Keyword.t()
) :: Ecto.Schema.t()

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

Link to this callback

insert(struct_or_changeset, opts)

View Source (optional)
@callback 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. If more than one database operation is required, they're automatically wrapped in a transaction.

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. It accepts a list of fields to be returned from the database. When true, returns all fields, including those marked as load_in_query: false. When false, no extra fields are returned. It will always include all fields in read_after_writes as well as any autogenerated id. Be aware that the fields returned from the database overwrite what was supplied by the user. Any field not returned by the database will be present with the original value supplied by the user. Not all databases support this option and it may not be available during upserts. See the "Upserts" section for more information.

  • :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 and any @schema_prefix set on any schemas. Also, the @schema_prefix for the parent record will override all default @schema_prefixs set in any child schemas for associations.

  • :on_conflict - It may be one of :raise (the default), :nothing, :replace_all, {:replace_all_except, fields}, {:replace, fields}, a keyword list of update instructions or an Ecto.Query query for updates. See the "Upserts" section for more information.

  • :conflict_target - A list of column names to verify for conflicts. It is expected those columns to have unique indexes on them that may conflict. If none is specified, the conflict target is left up to the database. It may also be {:unsafe_fragment, binary_fragment} to pass any expression to the database without any sanitization, this is useful for partial index or index with expressions, such as {:unsafe_fragment, "(coalesce(firstname, ""), coalesce(lastname, "")) WHERE middlename IS NULL"} for ON CONFLICT (coalesce(firstname, ""), coalesce(lastname, "")) WHERE middlename IS NULL SQL query.

  • :stale_error_field - The field where stale errors will be added in the returning changeset. This option can be used to avoid raising Ecto.StaleEntryError.

  • :stale_error_message - The message to add to the configured :stale_error_field when stale errors happen, defaults to "is stale".

  • :allow_stale - Doesn't error if insert is stale. Defaults to false. This may happen if there are rules or triggers in the database that rejects the insert operation.

See the "Shared options" section at the module documentation for more options.

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 schema/changeset, including fields not explicitly set in the changeset, such as IDs and autogenerated timestamps (inserted_at and updated_at). Do not use this option if you have auto-incrementing primary keys, as they will also be replaced. You most likely want to use {:replace_all_except, [:id]} or {:replace, fields} explicitly instead. This option requires a schema

  • {:replace_all_except, fields} - same as above except the given fields are not replaced. This option requires a schema

  • {:replace, fields} - replace only specific columns. This option requires :conflict_target

  • 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. Similarly to update_all/3, auto generated values, such as timestamps are not automatically updated. If the struct cannot be found, Ecto.StaleEntryError will be raised.

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)

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. If the primary key is auto-generated by the database, the primary key in the ignored record will be nil if there was no insertion. For example, if you use the default primary key (which has name :id and a type of :id), then ignored.id above will be nil if there was no insertion.

If your id is generated by your application (typically the case for :binary_id) or if you pass another value for :on_conflict, detecting if an insert or update happened is slightly more complex, as the database does not actually inform us what 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 the ones in the struct/changeset, including autogenerated fields such as inserted_at and updated_at:

    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. (Note that it will only read from the database if at least one field is updated).

    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)

Because of the inability to know if the struct is up to date or not, inserting a struct with associations and using the :on_conflict option at the same time is not recommended, as Ecto will be unable to actually track the proper status of the association.

Advanced Upserts

Using an Ecto.Query for :on_conflict can allow us to use more advanced database features. For example, PostgreSQL supports conditional upserts like DO UPDATE SET title = EXCLUDED.title, version = EXCLUDED.version WHERE EXCLUDED.version > post.version. This means that the title and version will be updated only if the proposed row has a greater version value than the existing row.

Ecto can support this as follows:

conflict_query =
  from(p in Post,
    update: [set: [
      title: fragment("EXCLUDED.title"),
      version: fragment("EXCLUDED.version")
      ]],
    where: fragment("EXCLUDED.version > ?", p.version)
  )

MyRepo.insert(
  %Post{id: 1, title: "Ecto Upserts (Dance Remix)", version: 2},
  conflict_target: [:id],
  on_conflict: conflict_query
)
Link to this callback

insert!(struct_or_changeset, opts)

View Source (optional)
@callback insert!(
  struct_or_changeset :: Ecto.Schema.t() | Ecto.Changeset.t(),
  opts :: Keyword.t()
) :: Ecto.Schema.t()

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_or_query, opts)

View Source (optional)
@callback insert_all(
  schema_or_source :: binary() | {binary(), module()} | module(),
  entries_or_query ::
    [%{required(atom() | String.t()) => value} | Keyword.t(value)]
    | Ecto.Query.t(),
  opts :: Keyword.t()
) :: {non_neg_integer(), nil | [term()]}
when value: term() | Ecto.Query.t()

Inserts all entries into the repository.

It expects a schema module (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. The keys of the entries are the field names as atoms, when a schema module is specified in the first argument. Otherwise, the keys can be either atoms or strings representing the names of the columns in the underlying datastore. The value should be the respective value for the field type or, optionally, an Ecto.Query that returns a single entry with a single value.

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 module is given, the entries given will be properly dumped before being sent to the database. If the schema primary key has type :id or :binary_id, it will be handled either at the adapter or the storage layer. However any other primary key type or autogenerated value, like Ecto.UUID and timestamps, won't be autogenerated when using insert_all/3. You must set those fields explicitly. 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 auto generated values 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 module, 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 schema. 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 and any @schema_prefix set in the schema.

  • :on_conflict - It may be one of :raise (the default), :nothing, :replace_all, {:replace_all_except, fields}, {:replace, fields}, a keyword list of update instructions or an Ecto.Query query for updates. See the "Upserts" section for more information.

  • :conflict_target - A list of column names to verify for conflicts. It is expected those columns to have unique indexes on them that may conflict. If none is specified, the conflict target is left up to the database. It may also be {:unsafe_fragment, binary_fragment} to pass any expression to the database without any sanitization, this is useful for partial index or index with expressions, such as {:unsafe_fragment, "(coalesce(firstname, ''), coalesce(lastname, '')) WHERE middlename IS NULL"} for ON CONFLICT (coalesce(firstname, ''), coalesce(lastname, '')) WHERE middlename IS NULL SQL query.

  • :placeholders - A map with placeholders. This feature is not supported by all databases. See the "Placeholders" section for more information.

See the "Shared options" section at the module documentation for remaining options.

Source query

A query can be given instead of a list with entries. This query needs to select into a map containing only keys that are available as writeable columns in the schema. This will query and insert the values all inside one query, without another round trip to the application.

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"}])

query = from p in Post,
  join: c in assoc(p, :comments),
  select: %{
    author_id: p.author_id,
    posts: count(p.id, :distinct),
    interactions: sum(p.likes) + count(c.id)
  },
  group_by: p.author_id
MyRepo.insert_all(AuthorStats, query)

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 schema/changeset, including fields not explicitly set in the changeset, such as IDs and autogenerated timestamps (inserted_at and updated_at). Do not use this option if you have auto-incrementing primary keys, as they will also be replaced. You most likely want to use {:replace_all_except, [:id]} or {:replace, fields} explicitly instead. This option requires a schema

  • {:replace_all_except, fields} - same as above except the given fields are not replaced. This option requires a schema

  • {:replace, fields} - replace only specific columns. This option requires :conflict_target

  • 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 will return the number of entries inserted on insert_all/3. However, when the :on_conflict option is specified, Postgres and MySQL will return different results.

Postgres will only count a row if it was affected and will return 0 if no new entry was added.

MySQL will return, at a minimum, the number of entries attempted. For example, if :on_conflict is set to :nothing, MySQL will return the number of entries attempted to be inserted, even when no entry was added.

Also note that if :on_conflict is a query, MySQL will return the number of attempted entries plus the number of entries modified by the UPDATE query.

Placeholders

Passing in a map for the :placeholders allows you to send less data over the wire when you have many entries with the same value for a field. To use a placeholder, replace its value in each of your entries with {:placeholder, key}, where key is the key you are using in the :placeholders option map. For example:

placeholders = %{blob: large_blob_of_text(...)}

entries = [
  %{title: "v1", body: {:placeholder, :blob}},
  %{title: "v2", body: {:placeholder, :blob}}
]

Repo.insert_all(Post, entries, placeholders: placeholders)

Keep in mind that:

  • placeholders cannot be nested in other values. For example, you cannot put a placeholder inside an array. Instead, the whole array has to be the placeholder

  • a placeholder key can only be used with columns of the same type

  • placeholders require a database that supports index parameters, so they are not currently compatible with MySQL

Link to this callback

insert_or_update(changeset, opts)

View Source (optional)
@callback 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 query and any @schema_prefix set any schemas. Also, the @schema_prefix for the parent record will override all default @schema_prefixs set in any child schemas for associations.
  • :stale_error_field - The field where stale errors will be added in the returning changeset. This option can be used to avoid raising Ecto.StaleEntryError. Only applies to updates.
  • :stale_error_message - The message to add to the configured :stale_error_field when stale errors happen, defaults to "is stale". Only applies to updates.
  • :allow_stale - Doesn't error if delete is stale. Defaults to false. Only applies to updates.

See the "Shared options" section at the module documentation for more options.

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 (optional)
@callback insert_or_update!(changeset :: Ecto.Changeset.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t()

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

Link to this callback

load(schema_or_map, data)

View Source
@callback load(
  schema_or_map :: module() | map(),
  data :: map() | Keyword.t() | {list(), list()}
) :: Ecto.Schema.t() | map()

Loads data into a schema or a map.

The first argument can be a schema module or a map (of types). The first argument 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.

To load data from non-database sources, use Ecto.embedded_load/3.

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

preload(structs_or_struct_or_nil, preloads, opts)

View Source (optional)
@callback 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. Preload assumes each association has the same nested associations already loaded. If this is not the case, it is possible to lose information. For example:

comment1 = TestRepo.preload(comment1, [author: [:permalink]])
TestRepo.preload([comment1, comment2], :author)

If both comments are associated to the same author, the first comment will lose its nested :permalink association because the second comment does not have it preloaded. To avoid this, you must preload the nested associations as well.

If you want to reset the loaded fields, see Ecto.reset_fields/2.

Options

  • :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 first struct in the given collection. This option allows the prefix to be changed.
  • :on_preloader_spawn - when preloads are done in parallel, this function will be called in the processes that perform the preloads. This can be useful for context propagation for traces.

See the "Shared options" section at the module documentation for more options.

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: []]

# You can mix atoms and keywords, but the atoms must come first
posts = Repo.preload posts, [:authors, comments: [:likes, replies: [:reactions]]]

# 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]}]

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

Link to this callback

reload(struct_or_structs, opts)

View Source (optional)
@callback reload(
  struct_or_structs :: Ecto.Schema.t() | [Ecto.Schema.t()],
  opts :: Keyword.t()
) :: Ecto.Schema.t() | [Ecto.Schema.t() | nil] | nil

Reloads a given schema or schema list from the database.

When using with lists, it is expected that all of the structs in the list belong to the same schema. Ordering is guaranteed to be kept. Results not found in the database will be returned as nil.

Example

MyRepo.reload(post)
%Post{}

MyRepo.reload([post1, post2])
[%Post{}, %Post{}]

MyRepo.reload([deleted_post, post1])
[nil, %Post{}]
Link to this callback

reload!(struct_or_structs, opts)

View Source (optional)
@callback reload!(struct_or_structs, opts :: Keyword.t()) :: struct_or_structs
when struct_or_structs: Ecto.Schema.t() | [Ecto.Schema.t()]

Similar to reload/2, but raises when something is not found.

When using with lists, ordering is guaranteed to be kept.

Example

MyRepo.reload!(post)
%Post{}

MyRepo.reload!([post1, post2])
[%Post{}, %Post{}]
Link to this callback

update(changeset, opts)

View Source (optional)
@callback 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 more than one database operation is required, they're automatically wrapped in a transaction.

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

If the struct cannot be found, Ecto.StaleEntryError 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

  • :returning - selects which fields to return. It accepts a list of fields to be returned from the database. When true, returns all fields, including those marked as load_in_query: false. When false, no extra fields are returned. It will always include all fields in read_after_writes. Be aware that the fields returned from the database overwrite what was supplied by the user. Any field not returned by the database will be present with the original value supplied by the user. Not all databases support this option.

  • :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 query and any @schema_prefix set on any schemas. Also, the @schema_prefix for the parent record will override all default @schema_prefixs set in any child schemas for associations.

  • :stale_error_field - The field where stale errors will be added in the returning changeset. This option can be used to avoid raising Ecto.StaleEntryError.

  • :stale_error_message - The message to add to the configured :stale_error_field when stale errors happen, defaults to "is stale".

  • :allow_stale - Doesn't error if update is stale. Defaults to false. This may happen if the struct has been deleted from the database before the update or if there is a rule or a trigger on the database that rejects the update operation.

See the "Shared options" section at the module documentation for more options.

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 (optional)
@callback update!(changeset :: Ecto.Changeset.t(), opts :: Keyword.t()) :: Ecto.Schema.t()

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

Transaction API

@callback checked_out?() :: boolean()

Returns true if a connection has been checked out.

This is true if inside a Ecto.Repo.checkout/2 or Ecto.Repo.transaction/2.

Examples

MyRepo.checked_out?
#=> false

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

MyRepo.checkout(fn ->
  MyRepo.checked_out? #=> true
end)
Link to this callback

checkout(function, opts)

View Source
@callback checkout((-> result), opts :: Keyword.t()) :: result when result: var

Checks out a connection for the duration of the function.

It returns the result of the function. This is useful when you need to perform multiple operations against the repository in a row and you want to avoid checking out the connection multiple times.

checkout/2 and transaction/2 can be combined and nested multiple times. If checkout/2 is called inside the function of another checkout/2 call, the function is simply executed, without checking out a new connection.

Options

See the "Shared options" section at the module documentation for more options.

Link to this callback

in_transaction?()

View Source (optional)
@callback in_transaction?() :: boolean()

Returns true if the current process is inside a transaction.

If you are using the Ecto.Adapters.SQL.Sandbox in tests, note that even though each test is inside a transaction, in_transaction?/0 will only return true inside transactions explicitly created with transaction/2. This is done so the test environment mimics dev and prod.

Examples

MyRepo.in_transaction?
#=> false

MyRepo.transaction(fn ->
  MyRepo.in_transaction? #=> true
end)
Link to this callback

rollback(value)

View Source (optional)
@callback rollback(value :: any()) :: no_return()

Rolls back the current transaction.

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

Note that calling rollback causes the code in the transaction to stop executing.

Link to this callback

transaction(fun_or_multi, opts)

View Source (optional)
@callback transaction(
  fun_or_multi :: (... -> any()) | Ecto.Multi.t(),
  opts :: Keyword.t()
) ::
  {:ok, any()} | {:error, any()} | Ecto.Multi.failure()

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

Use with function

transaction/2 can be called with both a function of arity zero or one. The arity zero function will just be executed as is:

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)

While the arity one function will receive the repo of the transaction as its first argument:

MyRepo.transaction(fn repo ->
  repo.insert!(%Post{})
end)

If an Elixir exception occurs the transaction will be rolled back and the exception will bubble up from the transaction function. If no exception occurs, the transaction is 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}.

Nested transactions

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 aborted, guaranteeing nothing will be committed.

Below is an example of how rollbacks work with nested transactions:

{:error, :rollback} =
  MyRepo.transaction(fn ->
    {:error, :posting_not_allowed} =
      MyRepo.transaction(fn ->
        # This function call causes the following to happen:
        #
        #   * the transaction is rolled back in the database,
        #   * code execution is stopped within the current function,
        #   * and the value, passed to `rollback/1` is returned from
        #     `MyRepo.transaction/1` as the second element in the error
        #     tuple.
        #
        MyRepo.rollback(:posting_not_allowed)

        # `rollback/1` stops execution, so code here won't be run
      end)

    # The transaction here is now aborted and any further
    # operation will raise an exception.
  end)

See the "Aborted transactions" section for more examples of aborted transactions and how to handle them.

In practice, managing nested transactions can become complex quickly. For this reason, Ecto provides Ecto.Multi for composing transactions.

Use with Ecto.Multi

transaction/2 also accepts the Ecto.Multi struct as first argument. Ecto.Multi allows you to compose transactions operations, step by step, and manage what happens in case of success or failure.

When an Ecto.Multi is given to this function, a transaction will be started, all operations applied and in case of success committed returning {:ok, changes}:

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

In case of any errors the transaction will be rolled back and {:error, failed_operation, failed_value, changes_so_far} will be returned.

Explore the Ecto.Multi documentation to learn more and find detailed examples.

Aborted transactions

When an operation inside a transaction fails, the transaction is aborted in the database. For instance, if you attempt an insert that violates a unique constraint, the insert fails and the transaction is aborted. In such cases, any further operation inside the transaction will raise exceptions.

Take the following transaction as an example:

Repo.transaction(fn repo ->
  case repo.insert(changeset) do
    {:ok, post} ->
      repo.insert(%Status{value: "success"})

    {:error, changeset} ->
      repo.insert(%Status{value: "failure"})
  end
end)

If the changeset is valid, but the insert operation fails due to a database constraint, the subsequent repo.insert(%Status{value: "failure"}) operation will raise an exception because the database has already aborted the transaction and thus making the operation invalid. In Postgres, the exception would look like this:

** (Postgrex.Error) ERROR 25P02 (in_failed_sql_transaction) current transaction is aborted, commands ignored until end of transaction block

If the changeset is invalid before it reaches the database due to a validation error, no statement is sent to the database, an :error tuple is returned, and repo.insert(%Status{value: "failure"}) operation will execute as usual.

We have two options to deal with such scenarios:

If you don't want to change the semantics of your code, you can also use the savepoints feature by passing the :mode option like this: repo.insert(changeset, mode: :savepoint). In case of an exception, the transaction will rollback to the savepoint and prevent the transaction from failing.

Another alternative is to handle this operation outside of the transaction. For example, you can choose to perform an explicit repo.rollback call in the {:error, changeset} clause and then perform the repo.insert(%Status{value: "failure"}) outside of the transaction. You might also consider using Ecto.Multi, as they automatically rollback whenever an operation fails.

Working with processes

The transaction is per process. A separate process started inside a transaction won't be part of the same transaction and will use a separate connection altogether.

When using the Ecto.Adapters.SQL.Sandbox in tests, while it may be possible to share the connection between processes, the parent process will typically hold the connection until the transaction completes. This may lead to a deadlock if the child process attempts to use the same connection. See the docs for Ecto.Adapters.SQL.Sandbox for more information.

Options

See the "Shared options" section at the module documentation for more options.

Process API

@callback get_dynamic_repo() :: atom() | pid()

Returns the atom name or pid of the current repository.

See put_dynamic_repo/1 for more information.

Link to this callback

put_dynamic_repo(name_or_pid)

View Source
@callback put_dynamic_repo(name_or_pid :: atom() | pid()) :: atom() | pid()

Sets the dynamic repository to be used in further interactions.

Sometimes you may want a single Ecto repository to talk to many different database instances. By default, when you call MyApp.Repo.start_link/1, it will start a repository with name MyApp.Repo. But if you want to start multiple repositories, you can give each of them a different name:

MyApp.Repo.start_link(name: :tenant_foo, hostname: "foo.example.com")
MyApp.Repo.start_link(name: :tenant_bar, hostname: "bar.example.com")

You can also start repositories without names by explicitly setting the name to nil:

MyApp.Repo.start_link(name: nil, hostname: "temp.example.com")

However, once the repository is started, you can't directly interact with it, since all operations in MyApp.Repo are sent by default to the repository named MyApp.Repo. You can change the default repo at compile time with:

use Ecto.Repo, default_dynamic_repo: :name_of_repo

Or you can change it anytime at runtime by calling put_dynamic_repo/1:

MyApp.Repo.put_dynamic_repo(:tenant_foo)

From this moment on, all future queries done by the current process will run on :tenant_foo.

@callback start_link(opts :: Keyword.t()) ::
  {:ok, pid()} | {:error, {:already_started, pid()}} | {:error, term()}

Starts the Repo supervision tree.

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 stop(timeout()) :: :ok

Shuts down the repository.

Config API

@callback __adapter__() :: Ecto.Adapter.t()

Returns the adapter tied to the repository.

@callback config() :: Keyword.t()

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 :runtime. It does not consider the options given on start_link/1.

User callbacks

Link to this callback

default_options(operation)

View Source
@callback default_options(operation) :: Keyword.t()
when operation:
       :all
       | :delete
       | :delete_all
       | :insert
       | :insert_all
       | :insert_or_update
       | :preload
       | :reload
       | :stream
       | :transaction
       | :update
       | :update_all

A user customizable callback invoked to retrieve default options for operations.

This can be used to provide default values per operation that have higher precedence than the values given on configuration or when starting the repository. It can also be used to set query specific options, such as :prefix.

This callback is invoked as the entry point for all repository operations. For example, if you are executing a query with preloads, this callback will be invoked once at the beginning, but the options returned here will be passed to all following operations.

Link to this callback

init(context, config)

View Source (optional)
@callback init(context :: :supervisor | :runtime, config :: Keyword.t()) ::
  {:ok, Keyword.t()} | :ignore

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

This callback is available for backwards compatibility purposes. Most runtime configuration in Elixir today can be done via config/runtime.exs.

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 :runtime 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

prepare_query(operation, query, opts)

View Source (optional)
@callback prepare_query(operation, query :: Ecto.Query.t(), opts :: Keyword.t()) ::
  {Ecto.Query.t(), Keyword.t()}
when operation: :all | :update_all | :delete_all | :stream | :insert_all

A user customizable callback invoked for query-based operations.

This callback can be used to further modify the query and options before it is transformed and sent to the database.

This callback is invoked for all query APIs, including the stream functions. It is also invoked for insert_all if a source query is given. It is not invoked for any of the other schema functions.

Examples

Let's say you want to filter out records that were "soft-deleted" (have deleted_at column set) from all operations unless an admin is running the query; you can define the callback like this:

@impl true
def prepare_query(_operation, query, opts) do
  if opts[:admin] do
    {query, opts}
  else
    query = from(x in query, where: is_nil(x.deleted_at))
    {query, opts}
  end
end

And then execute the query:

Repo.all(query)              # only non-deleted records are returned
Repo.all(query, admin: true) # all records are returned

The callback will be invoked for all queries, including queries made from associations and preloads. It is not invoked for each individual join inside a query.

Types

Functions

@spec all_running() :: [atom() | pid()]

Returns all running Ecto repositories.

The list is returned in no particular order. The list contains either atoms, for named Ecto repositories, or PIDs.