JUXT Blog - Crux Jupiter Assignment: Delete Transactions

Introduction

This is the delete installment of the Crux tutorial.

We shall assume you have a Crux standalone node set up locally and are now comfortable with put operations and basic datalog queries. If this is not the case, you can find all you need to know on Earth, Pluto and Mercury. Click on a destination above to take you there.

Arrival on Jupiter

You approach Jupiter and marvel at its bands. You wish you could have seen it this close before the Great Red Spot dissipated.

As you enter the Jovian atmosphere your communications panel lights up with the now expected, but rather terse message from boundary control.

Jupiter’s boundary is controlled.

If you wish to enter, present your papers now.

— Zeus Confederacy

The government is asking to see your flight manifest.

Choose your path:

You have your manifest

You do not have your manifest

You have permission to land

You do not have permission to land. You must return to Saturn and fill in your manifest.

Space Port

It’s a turbulent ride down to the space port. To take your mind off the colossal storm outside, you check the Crux manual for the delete operation.

Currently there are only four transaction operations in Crux: put, delete, match and evict.

Operation Description

put

Writes a version of a document

delete

Deletes a version of a document

match

Stops a transaction if the precondition is not met.

evict

Removes a document entirely

Delete:

The delete operation takes a valid eid with the option to include a start and end valid-time.

Time in Crux is denoted #inst "yyyy-MM-ddThh:mm:ss". For example, 9:30 pm on January 2^nd 1999 would be written:

#inst "1999-01-02T21:30:00".

The document will be deleted as of the transaction time, or between the start and end valid-time if provided. Historical versions of the document that fall outside of the valid-time window will be preserved.

A complete delete transaction has the form:

[:crux.tx/delete eid valid-time-start valid-time-end]

Operation	Description
`put`	Writes a version of a document
`delete`	Deletes a version of a document
`match`	Stops a transaction if the precondition is not met.
`evict`	Removes a document entirely

— Crux manual
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Assignment

You land on the raised platform and open your job ticket:

Ticket

Task	`Remove assigned clients for leaver.`
Company	`Helios Banking Inc.`
Contact	`Kaarlang`
Submitted	`2115-02-10T13:38:20`
Additional information	`Help Kaarlang delete client history from his Crux node in accordance with Earth data protection laws.`
Attachments	—

As you leave your ship, you are met by the martian Kaarlang:

Hi there, I believe you’re here to help me.

I’ve been told I need to delete my client history with today being my last day.

Is this something you can help me with?

— Kaarlang
Helios Banking Inc.

Choose your path

"Yes, we’ll work together to do this."

"I’m not sure how to even begin."

Kaarlang gives you his client history so you can sync up your Crux node.

(crux/submit-tx
 node [[:crux.tx/put {:crux.db/id :kaarlang/clients
                      :clients [:encompass-trade]}
        #inst "2110-01-01T09"
        #inst "2111-01-01T09"]

       [:crux.tx/put {:crux.db/id :kaarlang/clients
                      :clients [:encompass-trade :blue-energy]}
        #inst "2111-01-01T09"
        #inst "2113-01-01T09"]

       [:crux.tx/put {:crux.db/id :kaarlang/clients
                      :clients [:blue-energy]}
        #inst "2113-01-01T09"
        #inst "2114-01-01T09"]

       [:crux.tx/put {:crux.db/id :kaarlang/clients
                      :clients [:blue-energy :gold-harmony :tombaugh-resources]}
        #inst "2114-01-01T09"
        #inst "2115-01-01T09"]])
;;=> #:crux.tx{:tx-id 0, :tx-time #inst "2020-06-18T15:55:00.894-00:00"}

To get a good visual aid, you show Kaarlang how to view his client history. This way you both can see when the clients are deleted. You use the option :with-docs? to show the content of the doc.

(crux/entity-history
 (crux/db node #inst "2116-01-01T09")
 :kaarlang/clients
 :desc
 {:with-docs? true})
#_#_
=> [{:crux.tx/tx-time #inst "2020-06-18T15:57:28.900-00:00",
    :crux.tx/tx-id 1,
    :crux.db/valid-time #inst "2114-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "d4bca6c78409d9d40ee42319a8aec32bffad9030",
    :crux.db/doc
    {:crux.db/id :kaarlang/clients,
     :clients [:blue-energy :gold-harmony :tombaugh-resources]}}
   {:crux.tx/tx-time #inst "2020-06-18T15:57:28.900-00:00",
    :crux.tx/tx-id 1,
    :crux.db/valid-time #inst "2113-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "000e5b775b55d06f0bddc77d736184284aa1e4e9",
    :crux.db/doc {:crux.db/id :kaarlang/clients, :clients [:blue-energy]}}
   {:crux.tx/tx-time #inst "2020-06-18T15:57:28.900-00:00",
    :crux.tx/tx-id 1,
    :crux.db/valid-time #inst "2111-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "cd71551fe21219db59067ce7483370fdebaae8b0",
    :crux.db/doc
    {:crux.db/id :kaarlang/clients, :clients [:encompass-trade :blue-energy]}}
   {:crux.tx/tx-time #inst "2020-06-18T15:57:28.900-00:00",
    :crux.tx/tx-id 1,
    :crux.db/valid-time #inst "2110-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "5ec42ea653288e01e1a9d7d2068b4658416177e0",
    :crux.db/doc {:crux.db/id :kaarlang/clients, :clients [:encompass-trade]}}]

The result shows the names of the clients that have been assigned to Kaarlang since he started at the company in 2110.

Next you delete the whole history of clients buy choosing a start and end valid-time that spans his entire employment time.

(crux/submit-tx
 node [[:crux.tx/delete :kaarlang/clients #inst "2110-01-01" #inst "2116-01-01"]])
;;=> #:crux.tx{:tx-id 1, :tx-time #inst "2020-06-18T15:59:38.323-00:00"}

Using the same method as before you show Kaarlang the effect of this operation.

(crux/entity-history
 (crux/db node #inst "2116-01-01T09")
 :kaarlang/clients
 :desc
 {:with-docs? true})
#_#_
=> [{:crux.tx/tx-time #inst "2020-06-18T15:59:38.323-00:00",
    :crux.tx/tx-id 2,
    :crux.db/valid-time #inst "2115-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "0000000000000000000000000000000000000000",
    :crux.db/doc nil}
   {:crux.tx/tx-time #inst "2020-06-18T15:59:38.323-00:00",
    :crux.tx/tx-id 2,
    :crux.db/valid-time #inst "2114-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "0000000000000000000000000000000000000000",
    :crux.db/doc nil}
   {:crux.tx/tx-time #inst "2020-06-18T15:59:38.323-00:00",
    :crux.tx/tx-id 2,
    :crux.db/valid-time #inst "2113-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "0000000000000000000000000000000000000000",
    :crux.db/doc nil}
   {:crux.tx/tx-time #inst "2020-06-18T15:59:38.323-00:00",
    :crux.tx/tx-id 2,
    :crux.db/valid-time #inst "2111-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "0000000000000000000000000000000000000000",
    :crux.db/doc nil}
   {:crux.tx/tx-time #inst "2020-06-18T15:59:38.323-00:00",
    :crux.tx/tx-id 2,
    :crux.db/valid-time #inst "2110-01-01T09:00:00.000-00:00",
    :crux.db/content-hash #crux/id "0000000000000000000000000000000000000000",
    :crux.db/doc nil}
   {:crux.tx/tx-time #inst "2020-06-18T15:59:38.323-00:00",
    :crux.tx/tx-id 2,
    :crux.db/valid-time #inst "2110-01-01T00:00:00.000-00:00",
    :crux.db/content-hash #crux/id "0000000000000000000000000000000000000000",
    :crux.db/doc nil}]

Kaarlang is impressed it is that easy. You point out that there are no longer any documents attached to the transactions.

I am grateful that you took the time to show me this.

Today is a sad day for me as I have very much enjoyed my time here.

Although, I was expecting to hear from a friend before I left. There is a very important message that I am waiting for.

— Kaarlang
Speaking from the heart

You remember the secret note in your pocket and pass it to Kaarlang.

The Secret Note

Kaarlang reads the note.

He looks at you with the a peculiar facial expression.

This is the note I was waiting for.

It has information about the a top secret stellar transport shuttle.

If you are interested in a great adventure, the shuttle comes once every hundred years or so to take a select few to a nearby star system. The system is home to a mysterious hyper-intelligent form of life.

I’m sure there would be a place for you if you were willing to help out. The passengers on the shuttle have the right to be forgotten. We need someone that can remove the passengers data from the solar system.

What do you think?

— Kaarlang

Choose Your Path

"That sounds like a great opportunity, I’m in."		"No thanks, not for me."
You head off to the secret location of the shuttle.		You choose not to got with Kaarlang. You continue working for Helios Banking Inc. for the rest of your days.

"That sounds like a great opportunity, I’m in."

"No thanks, not for me."

You head off to the secret location of the shuttle.

You choose not to got with Kaarlang. You continue working for Helios Banking Inc. for the rest of your days.

Crux Jupiter Assignment: Delete Transactions

Johanna Antonelli