{:crux.db/id :dbpedia.resource/Pablo-Picasso
:name "Pablo"
:last-name "Picasso"}Liking cljdoc? Tell your friends :D
Transactions
Overview
There are four transaction (write) operations:
| Operation | Purpose |
|---|---|
| Write a version of a document |
| Compare and swap the version of a document, if that version is as expected |
| Deletes the specific document at a given |
| Evicts a document entirely, including all historical versions |
A document looks like this:
In practice when using Crux, one calls crux.db/submit-tx with a
sequence of transaction operations:
[[:crux.tx/put
{:crux.db/id :dbpedia.resource/Pablo-Picasso
:name "Pablo"
:last-name "Picasso"}
#inst "2018-05-18T09:20:27.966-00:00"]]If the transaction contains CAS operations, all CAS operations must pass their pre-condition check or the entire transaction is aborted. This happens at the query node during indexing, and not when submitting the transaction.
For operations containing documents, the id and the document are
hashed, and the operation and hash is submitted to the tx-topic in
the event log. The document itself is submitted to the doc-topic,
using its content hash as key. In Kafka, the doc-topic is compacted,
which enables later deletion of documents.
Valid IDs
The following types of :crux.db/id are allowed:
-
Keyword (e.g.
{:crux.db/id :my-id}or{:crux.db/id :dbpedia.resource/Pablo-Picasso}) -
UUID (e.g.
{:crux.db/id #uuid "6f0232d0-f3f9-4020-a75f-17b067f41203"}or{:crux.db/id #crux/id "6f0232d0-f3f9-4020-a75f-17b067f41203"}) -
URI (e.g.
{:crux.db/id #crux/id "mailto:crux@juxt.pro"}) -
URL (e.g.
{:crux.db/id #crux/id "https://github.com/juxt/crux"}), includinghttp,https,ftpandfileprotocols -
Maps (e.g.
{:crux.db/id #crux/id {:this :id-field}}) (Note: see issue #362).
The #crux/id reader literal will take any string and attempt to coerce it
into a valid ID. Use of #crux/id with a valid ID type will also work
(e.g. {:crux.db/id #crux/id :my-id}).
URIs and URLs are interpreted using Java classes (java.net.URI and java.net.URL respectively) and therefore you can also use these directly.
Put
Put’s a document into Crux. If a document already exists with the
given :crux.db/id, a new version of this document will be created at
the supplied valid time.
[:crux.tx/put
{:crux.db/id :dbpedia.resource/Pablo-Picasso :first-name :Pablo} (1)
#inst "2018-05-18T09:20:27.966-00:00"] (2)| 1 | The document itself. Note that the ID must be included as part of the document. |
| 2 | valid time |
Note that valid time is optional and defaults to transaction time,
which is taken from the Kafka log.
Crux currently writes into the past at a single point, so to overwrite several versions or a range in time, one is required to submit a transaction containing several operations.
CAS
The CAS operation (compare and swap) swaps an existing document version with a newer one, if the existing document is as expected.
[:crux.tx/cas
{..} (1)
{..} (2)
#inst "2018-05-18T09:21:31.846-00:00"] (3)| 1 | Expected Document |
| 2 | New document |
| 3 | valid time |
Delete
Deletes a document at a given valid time. Historical version of the
document will still be available.
[:crux.tx/delete :dbpedia.resource/Pablo-Picasso
#inst "2018-05-18T09:21:52.151-00:00"]Evict
Evicts a document from Crux. Historical versions of the documents will no longer be available.
[:crux.tx/evict :dbpedia.resource/Pablo-Picasso]Can you improve this documentation? These fine people already did:
Jeremy Taylor, Jon Pither, Tom Taylor, James Henderson, Daniel Mason, Antonelli712, Ivan Fedorov & Malcolm SparksEdit on GitHub
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