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18 changes: 9 additions & 9 deletions pull_data.md
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Original file line number Diff line number Diff line change
@@ -1,14 +1,14 @@
## Pull

Datascript and Datomic both come with a special *Pull API* for pulling entity data at a more coarse grained level. The Pull API can be seen as a sort of *simple query* that is more batch oriented.
Datascript and Datomic both come with a special *Pull API* for pulling entity data at a more coarse-grained level. The Pull API can be seen as a sort of *simple query* that is more batch oriented.

The Pull API comes in two variants:
- Pull One
- Pull Many

### Select patterns

The Pull API uses patterns for selecing attributes.
The Pull API uses patterns for selecting attributes.
The special pattern `'*'` fetches *all* attributes.

### Limits
Expand Down Expand Up @@ -42,7 +42,7 @@ SQL: `["SELECT * FROM People WHERE People.id = ?", maksim-id]`

### Fetch entity by ID

`entity(db eid)`
`(d/entity db eid)`

### Pull and Query combined

Expand All @@ -51,21 +51,21 @@ Let's say we want to extract all entity data of all entities.

`(d/pull-many db '[*] (d/q '[:find ?e :where [?e]]))`

The `d/q` will match all entity ids in the db
Then `pull-many` pulls everything for all of them
The `d/q` will match all entity ids in the db.
Then `pull-many` pulls everything for all of them.

We can f.ex also use a pull to find attributes to be used in a `:find` clause.
As another example, we can use a pull to find attributes to be used in a `:find` clause.
Here we use `pull` on the `:aliases` attribute value `?a` in the `:where` clause to pull only `:name` and `:order` values, which will be used as the attributes to `find`.

```clj
;; query
(->>
(d/q '[:find [(pull ?a [:name :order]) ...]
:in $ ?e
(d/q '[:find [(pull ?a [:name :order]) ...]
:in $ ?e
:where [?e :aliases ?a]
db eid)
(sort-by :order)
(map :name))
```

We can then sort and map the query result independently (and/or include limit/paging logic).
We can then sort and map the query result independently (or include limiting or paging logic).