Table of Contents
fulltext
The fulltext function in Datomish supports sets of attributes or the special keyword :any.
To do a fulltext search that matches page titles or excerpts:
[(fulltext $ #{:page/title :page/excerpt} "something") [[?page]]]
To match any attribute at all:
[(fulltext $ :any "something") [[?entity]]]
Query inputs, ordering, and limits
<q supports binding values, specifying ordering conditions, and limiting the number of returned results.
Aggregates can be used as an ordering clause: for an aggregate expression like (max ?date), the ordering column is _max_date. In ClojureScript this is a keyword (:_max_date); in JS it's a string.
ClojureScript:
(d/<q
db
'[:find ?page ?url ?title ?excerpt
:in $ ?time
:where
[?save :save/page ?page]
[?save :save/savedAt ?instant]
[(> ?instant ?time)]
[?page :page/url ?url]
[(get-else $ ?save :save/title "") ?title]
[(get-else $ ?save :save/excerpt "") ?excerpt]]
{:limit limit
:inputs {:time 1234567890}
:order-by [[:instant :desc]]})
JS:
await db.q(
`[:find ?url (max ?date)
:in $
:where
[?page :page/url ?url]
[?page :page/visitedAt ?date]]`,
{"limit": 2, "order-by": [["_max_date", "desc"]]});
Simple schema
Datomish's JS API exposes a simple schema interface through db.ensureSchema. This accepts input with simplified string keys and values, like this:
{
"name": "pages",
"attributes": [
{"name": "page/url",
"type": "string",
"cardinality": "one",
"unique": "identity",
"doc": "A page's URL."},
{"name": "page/title",
"type": "string",
"cardinality": "one",
"fulltext": true,
"doc": "A page's title."},
{"name": "page/content",
"type": "string",
"cardinality": "one",
"fulltext": true,
"doc": "A snapshot of the page's content. Should be plain text."},
]
}
Lookup Refs
There's a small syntactic difference with how lookup refs are indicated in EDN. Where in Datomic they will be indicated as [:namespace/attr value], in Mentat they are represented as (lookup-ref :namespace/attr value).
This may be fixed in a future version of Mentat, see issue https://github.com/mozilla/mentat/issues/392.