Specs

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

Returns the adapter tied to the repository.

Specs

aggregate(
  queryable :: Ecto.Queryable.t(),
  aggregate :: :count,
  opts :: Keyword.t()
) :: term() | nil

Calculate the given aggregate.

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

• :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")

Specs

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/2 for general considerations and options.

Examples

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

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

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

Specs

all(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) :: [Ecto.Schema.t()]

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)

Specs

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.

Specs

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.

Specs

default_options(operation) :: Keyword.t()
when operation:
       :all
       | :insert_all
       | :update_all
       | :delete_all
       | :stream
       | :transaction
       | :insert
       | :update
       | :delete
       | :insert_or_update

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.

Specs

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 from db prior to call, Ecto.StaleEntryError 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 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".

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

Specs

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.

Specs

delete_all(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) ::
  {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 overrides the prefix set in the query and any @schema_prefix set in the schema.

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

Specs

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, schema: "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)

Specs

get(queryable :: Ecto.Queryable.t(), id :: term(), opts :: Keyword.t()) ::
  Ecto.Schema.t() | 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")

Specs

get!(queryable :: Ecto.Queryable.t(), id :: term(), opts :: Keyword.t()) ::
  Ecto.Schema.t()

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")

Specs

get_by(
  queryable :: Ecto.Queryable.t(),
  clauses :: Keyword.t() | map(),
  opts :: Keyword.t()
) :: Ecto.Schema.t() | 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")

Specs

get_by!(
  queryable :: Ecto.Queryable.t(),
  clauses :: Keyword.t() | map(),
  opts :: Keyword.t()
) :: Ecto.Schema.t()

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")

Specs

get_dynamic_repo() :: atom() | pid()

Returns the atom name or pid of the current repository.

See put_dynamic_repo/1 for more information.

Specs

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.

If you are trying to debug transaction-related code while using Ecto.Adapters.SQL.Sandbox, it may be more helpful to configure the database to log all statements and consult those logs.

Examples

MyRepo.in_transaction?
#=> false

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

Specs

init(context :: :supervisor | :runtime, 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 :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).

Specs

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. It accepts a list of fields to be returned from the database. When true, returns all fields. When false, no extra fields are returned. It will always include all fields in read_after_writes as well as any autogenerated id. 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 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 ON CONFLICT (coalesce(firstname, ""), coalesce(lastname, "")).
• :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".

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. 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)
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 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:

  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.

Specs

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.

Specs

insert_all(
  schema_or_source :: binary() | {binary(), module()} | module(),
  entries :: [map() | [{atom(), term() | Ecto.Query.t()}]],
  opts :: Keyword.t()
) :: {integer(), nil | [term()]}

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 and 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 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 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 ON CONFLICT (coalesce(firstname, ""), coalesce(lastname, "")).

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 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.

Specs

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.

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

Specs

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.

Specs

load(
  module_or_map :: module() | map(),
  data :: map() | Keyword.t() | {list(), list()}
) :: Ecto.Schema.t() | map()

Loads data into a struct or a map.

The first argument can be a a schema module, 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.

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{...}, ...]

Specs

one(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) ::
  Ecto.Schema.t() | 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")

Specs

one!(queryable :: Ecto.Queryable.t(), opts :: Keyword.t()) :: Ecto.Schema.t()

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.

Specs

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

• :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.

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: []]

# 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.

Specs

prepare_query(operation, query :: Ecto.Query.t(), opts :: Keyword.t()) ::
  {Ecto.Query.t(), Keyword.t()}
when operation: :all | :update_all | :delete_all | :stream

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 function, but it is not invoked for insert_all nor any of the 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

Specs

put_dynamic_repo(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.

Note this feature is experimental and may be changed or removed in future releases.

Specs

rollback(value :: any()) :: no_return()

Rolls back the current transaction.

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

Specs

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.

Specs

stop(timeout()) :: :ok

Shuts down the repository.

Specs

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)

Specs

transaction(
  fun_or_multi :: (... -> any()) | Ecto.Multi.t(),
  opts :: Keyword.t()
) ::
  {:ok, any()}
  | {:error, any()}
  | {:error, Ecto.Multi.name(), any(), %{required(Ecto.Multi.name()) => any()}}

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, while the arity one function will receive the repo of the transaction as its first argument, similar to Ecto.Multi.run/3.

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, transactions can be used with an Ecto.Multi struct. A 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 for more options.

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)

# When passing a function of arity 1, it receives the repository itself
MyRepo.transaction(fn repo -> 
  repo.insert!(%Post{})
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

Specs

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.

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. When false, no extra fields are returned. It will always include all fields in read_after_writes. 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 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".

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

Specs

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.

Specs

update_all(
  queryable :: Ecto.Queryable.t(),
  updates :: Keyword.t(),
  opts :: Keyword.t()
) :: {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 overrides the prefix set in the query and any @schema_prefix set in the schema.

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([])