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Attributes

Join and Prefetch
Columns
- Restrictions
- Examples
  - columns
  - +columns
Ordering
Naming Conventions
Select and As
Collapse

The attrs parameter is for attributes like sorting, joining and column definitions.

https://metacpan.org/pod/distribution/DBIx-Class/lib/DBIx/Class/ResultSet.pm#ATTRIBUTES

The IronAPI supports these options:

join and prefetch
(+)columns
(+)select
(+)as
order_by
group_by
collapse
having

This document will cover some of the options with specific examples.

The attrs parameter is for attributes like sorting, joining and column definitions.

https://metacpan.org/pod/distribution/DBIx-Class/lib/DBIx/Class/ResultSet.pm#ATTRIBUTES

This document will cover some of the options with specific examples.

Join and Prefetch

'join' will join another entity to the base resultset without fetching any of it's attributes. Prefetch will join and fetch all the attributes of the other entity.

Only references may be joined/prefetched. There are two ways to do this, depending on the direction of the reference:

An attribute of an entity is a reference to an attribute of another entity

Use the attribute name to join or prefetch it - system.entity.module is a reference to system.module.id:

POST /data/sytem/entity/query

{
    "attrs" : {"prefetch":"module"}
}

This fetches all the details of the linked module entry to each entity entry.

An attribute of an entity is being references by another attribute of a different entity

Use $model__$entity__$attribute to join it - system.module.id is being referenced by system.entity.module:

POST /data/system/module/query

{
  "attrs" : {"prefetch":"system__entity__module"}
}

This fetches all entity entries for a module and lists them under the module.

Restrictions

Keys and values may not contain spaces and must be found in the universe of the user.

Examples

Combined with query conditions:

(This will get all transitions which have the instance as pre_state and whose post_state is 2)

POST /data/system/state/query

{
    "conds" : {"system__transition__pre_state.post_state" : 2 },
    "attrs": {"prefetch" : "system__transition__pre_state"}
}

In contrast, a "join" instead of the "prefetch" will only return the data from the base table. The joined table(s) can be used in the search condition and only specific columns may be returned.

(select all columns from system.state and return only system.transition.name using system_transition_pre_state.post_state as search condition)

POST /data/system/state/query

{
    "conds" : {"system__transition__pre_state.post_state" : 2 },
    "attrs": {
                "join"     : "system__transition__pre_state",
                "+columns" : ["system__transition__pre_state.entity"]
             }
}

Joins and prefetches can be nested as deeply as needed:

POST #/data/system/state/query

{
    "attrs": { "prefetch" : [  "modifying_client",
                             { "system__transition__pre_state" : "entity" }
                            ]
              }
}

More documentation on joining can be found here:

https://metacpan.org/pod/release/RIBASUSHI/DBIx-Class-0.082840/lib/DBIx/Class/Manual/Joining.pod

Columns

columns defines which attributes should be fetched.

Restrictions

Values may not contain spaces and must be present in the users universe.

Examples

columns

Get only two columns of the base entity:

POST /data/system/entity/query

{
  "attrs": {
    "columns": [
      "id",
      "name"
    ]
  }
}

To get only one column from a joined entity:

POST /data/system/entity/query

{
  "attrs": {
    "join": "module",
    "columns": [
      "module.name"
    ]
  }
}

+columns

Use +columns to get all columns of the base table plus certain ones from joined tables:

{
  "attrs": {
    "join": "module",
    "+columns": [
      "module.name"
    ]
  }
}

Ordering

RESTRICTIONS: keys and values may not contain spaces.

Ordering can be defined by the "order_by" attribute:

{attrs : { "order_by" : "date_of_birth" }}

{attrs : { "order_by" : { "-asc" : "col1" }}

{attrs : { "order_by": ["colA", {"-asc" : "colB"}]}

The API will also support similarity:

{attrs : { {"order_by" : {"-similarity" : ["me.name","abc"]}}}

will be translated to DBIx::Class notation \[ 'me.name <-> ?', "abc" ]

which in turn will be translated to sql ORDER BY me.name <-> ? : "abc"

Any column from a joined/prefetched table or a column selected with "select" can be used.

More details can be found here:

https://metacpan.org/pod/distribution/DBIx-Class/lib/DBIx/Class/ResultSet.pm#order_by and https://metacpan.org/pod/release/ILMARI/SQL-Abstract-1.84/lib/SQL/Abstract.pm#ORDER_BY_CLAUSES

Naming Conventions

When referencing to a column, the name without the table prefix can be used as long as it is unique within the query. Otherwise, the table name (as used for joining the table) needs to be prefixed: system__transition__pre_state.id.

The table the search is based on is always referenced as "me", so to dismbiguate use the "me" prefix, for joined/prefetched tables use their name as a prefix:

#/data/system/state/query

{
    "conds" : { "system__transition__pre_state.id" : { "-between" : [1,100] } } ,
    "attrs" : {"prefetch" : ["modifying_client", { "system__transition__pre_state" : "entity" }]}
}

Select and As

RESTRICTIONS: keys and values may not contain spaces.

The "select" and "as" attribues allow even more flexibility to define exactly what should be returned than "columns" does.

"attrs" : {
    "join":   [ "contracts__working_time_constraint" ],
    "select": [ {"min" : "max_hours_per_day"} ],
    "as":     [ "min_max" ]
}

Generates:

SELECT MIN( max_hours_per_day )
FROM contracts.collective_agreement() me
LEFT JOIN contracts.working_time_constraint() contracts_working_time_constraint ON contracts_working_time_constraint.collective_agreement = me.id
LIMIT 10

Returns one row:

{
    "min_max": "9"
}

"+select" and "+as" are also available.

https://metacpan.org/pod/distribution/DBIx-Class/lib/DBIx/Class/ResultSet.pm#select

Collapse

When "collape" is set to a true value, indicates that any rows fetched from joined has_many relationships are to be aggregated into the corresponding "parent" object:

Parameters:

{
  "attrs" :
  {
    "collapse": "0",
    "join"    : ["contracts__working_time_constraint"],
    "+columns": ["contracts__working_time_constraint.id"]
  }
}

Reply:

[
    {
        "modification_time": "2017-09-20 08:38:17.652733",
        "name": "Kollektivvertrag Arbeiterinnen und Arbeiter im Hotel- und Gastgewerbe",
        "url": "https://www.wko.at/branchen/tourismus-freizeitwirtschaft/gastronomie/KV-Rahmen_Mai-2017.pdf",
        "instance_entity": "91",
        "contracts__working_time_constraint": {
            "id": "2"
        },
        "modifying_action": "325",
        "valid_from": "2017-01-05",
        "region": "1",
        "description": "Kollektivvertrag für Arbeiter im Hotel- und Gastgewerbe abgeschlossen zwischen dem Fachverband Gastronomie und dem Fachverband Hotellerie, beide 1045 Wien, Wiedner Hauptstraße 63, einerseits und der Gewerkschaft vida, 1020 Wien, Johann Böhm-Platz 1, andererseits.",
        "id": "1",
        "modifying_client": "1",
        "successor": null
    },
    {
        "modification_time": "2017-09-20 08:38:17.652733",
        "name": "Kollektivvertrag Arbeiterinnen und Arbeiter im Hotel- und Gastgewerbe",
        "url": "https://www.wko.at/branchen/tourismus-freizeitwirtschaft/gastronomie/KV-Rahmen_Mai-2017.pdf",
        "instance_entity": "91",
        "contracts__working_time_constraint": {
            "id": "1"
        },
        "modifying_action": "325",
        "valid_from": "2017-01-05",
        "region": "1",
        "description": "Kollektivvertrag für Arbeiter im Hotel- und Gastgewerbe abgeschlossen zwischen dem Fachverband Gastronomie und dem Fachverband Hotellerie, beide 1045 Wien, Wiedner Hauptstraße 63, einerseits und der Gewerkschaft vida, 1020 Wien, Johann Böhm-Platz 1, andererseits.",
        "modifying_client": "1",
        "id": "1",
        "successor": null
    }
]

Parameters:

{
  "attrs" :
  {
    "collapse": "1",
    "join"    : ["contracts__working_time_constraint"],
    "+columns": ["contracts__working_time_constraint.id"]
  }
}

Reply:

{
    "description": "Kollektivvertrag für Arbeiter im Hotel- und Gastgewerbe abgeschlossen zwischen dem Fachverband Gastronomie und dem Fachverband Hotellerie, beide 1045 Wien, Wiedner Hauptstraße 63, einerseits und der Gewerkschaft vida, 1020 Wien, Johann Böhm-Platz 1, andererseits.",
    "valid_from": "2017-01-05",
    "region": "1",
    "successor": null,
    "id": "1",
    "modifying_client": "1",
    "url": "https://www.wko.at/branchen/tourismus-freizeitwirtschaft/gastronomie/KV-Rahmen_Mai-2017.pdf",
    "modification_time": "2017-09-20 08:38:17.652733",
    "name": "Kollektivvertrag Arbeiterinnen und Arbeiter im Hotel- und Gastgewerbe",
    "instance_entity": "91",
    "contracts__working_time_constraint": [
        {
            "id": "1"
        },
        {
            "id": "2"
        }
    ],
    "modifying_action": "325"
}

Note that "prefetch" is a shortcut for "join", adding all columns from the joined related sources as "+columns" and setting "collapse" to a true value.

https://metacpan.org/pod/distribution/DBIx-Class/lib/DBIx/Class/ResultSet.pm#collapse