Drupal 7 Node --> Fields Mapping In Database

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I am trying to figure out how nodes are mapped back to the fields they contain for learning purposes. How is this done?

Arnettearney answered 14/10, 2011 at 20:9 Comment(0)

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In Drupal 7 you have entities and fields; fields are attached to entities. A node is an implementation of an entity (the node module implements hook_entity_info() and other such hooks) so it can have fields.

All field/entity relational data is stored in the tables field_data_field_x and field_revision_field_x or similar (the latter potentially storing revisions of field data if node revisions are enabled).

The entity_id column in those tables is the node's ID, and the bundle is the node's content type. The revision_id is the revision ID of the node, again only really useful if node revisions are enabled.

UPDATE

In Drupal terminology a content type is a bundle and bundles are attached to entities (in this case the node entity). When you create a new content type it gets stored in the node_type table, and when the caches are cleared (which invokes hook_entity_info on all modules) the node_entity_info() function builds up a list of bundles from the content types (have a look at the bit in that function that starts foreach (node_type_get_names() as $type => $name) {, node_type_get_names gets a list of all content types).

As discussed above fields can be attached to entities, so fields can be attached to nodes with a delta (if you like) of bundle.

Environ answered 14/10, 2011 at 20:18 Comment(5)

How does a content type that gets created in the GUI implement hook_entity_info? I understand how the field data gets stored, but how does the form get created? – Arnettearney 14/10, 2011 at 20:25

Is it field_config_instance that defines which fields go with what? – Arnettearney 14/10, 2011 at 20:34

@ChrisMuench: I've updated the answer let me know if you need any clarification it's quite complicated if you haven't delved around inside the core modules before! – Environ 14/10, 2011 at 20:36

Oh sorry I got the wrong end of the stick I think, yes field_config_instance is literally where the field and entity type/bundles are related – Environ 14/10, 2011 at 20:37

Minor addition. The field storage is pluggable, the field_data and field_revision tables are just the default implementation which is provided by field_storage.module. Other implementations for example allow to store field data in MongoDB. – Reseta 15/10, 2011 at 9:8

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In D7, for my case field_config_instance table provided me the required info.

Pinon answered 18/9, 2020 at 3:56 Comment(0)

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