Immutable data...base?

These are the slides for a talk I gave on the 6th of February at RubyFuza 2014.

Transcript

1. ROBERT STUTTAFORD
   CTO, COGNICIAN
   Notes: http://is.gd/imm_db
   #rubyfuza
   Immutable data…base?
   

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2. Clojure
   

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3. Lisp
   Functional
   Immutable
   Dynamic
   Java & JS VMs
   OSS, 7 years old
   

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4. Lithp ... er, Lisp
   

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5. Functions are the unit of composition
   Created, stored, passed around for
   use by higher order functions, e.g. reduce.
   !
   Prefer to use pure functions
   Those with no side-effects or I/O.
   Easier to reason about, test, and compose.
   Functional programming
   

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6. Define and call functions
   

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7. Immutable, persistent data structures
   Once defined, can’t change ‘under’ you.
   Changes create copies.
   Copies share structure internally.
   Far, FAR easier to reason about!
   

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8. This is what
   mutable state
   feels like, now!
   

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9. Clojure’s collections
   

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10. Prefer to pass unadorned data
    through mostly pure functions,
    !
    rather than creating typed instances
    and mutating in place via methods.
    !
    Then, both the data and the logic
    are easier to compose and test!
    TL;DR
    

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11. Datomic
    

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12. Datomic is a database of
    flexible, time-based facts,
    supporting queries and joins,
    with elastic scalability,
    and ACID transactions.
    

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13. JVM, has REST API
    Closed source :-(
    Proprietary
    Paid licenses
    Free editions :-)
    Datomic
    

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14. Transactor

    Only 1 process
    Datomic’s architecture
    Consistent writes to storage
    Indexing
    Reads only while transacting
    

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15. Storage
    Datomic’s architecture
    Consistent writes to storage
    Indexing
    Reads only while transacting
    Abstracted, can use any of:

    Internal: In memory, on disk with transactor

    External: SQL, Riak, DynamoDB, and more
    Transactor

    Only 1 process
    

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16. Storage
    Peer
    Up to 30 procs
    Abstracted, can use any of:

    Internal: In memory, on disk with transactor

    External: SQL, Riak, DynamoDB, and more
    Reads from storage
    Inside your JVM app’s process
    Transparently cache from storage

    in local memory to satisfy reads
    Datomic’s architecture
    Consistent writes to storage
    Indexing
    Reads only while transacting
    Transactor

    Only 1 process
    

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17. Storage Query
    1-64 peers
    Datomic’s architecture
    Memcached
    2nd tier cache
    Peers look here before storage
    (paid licenses only)
    Paid licenses support high-availability
    transactor failover.
    Transactor

    Only 1 process
    

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18. Datomic’s data model
    [entity attr value]
    !
    !
    Entities have attributes with values.
    Each EAV combination is a ‘datom’.
    Entities typically have many datoms.
    

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19. Datomic’s data model
    [entity attr value]
    !
    [123 :name “Robert”]
    [123 :likes “coffee”]
    

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20. Datomic’s data model
    [entity attr value tx]
    !
    !
    But what about time?
    

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21. Datomic’s data model
    [entity attr value tx]
    !
    [123 :name “Robert” 456]
    [123 :likes “coffee” 456]
    [456 :tx-timestamp “2014-02-06”]
    Each datom refers to the
    transaction that created it.
    Transactions are also entities!
    

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22. Datomic’s data model
    [entity attr value tx]
    !
    [123 :likes “coffee” 456]
    [456 :timestamp “2014-02-06”]
    [123 :likes “beer” 789]
    [789 :timestamp “2014-02-07”]
    

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23. Datomic’s data model
    Schema defines only how
    attribute’s values behave.
    !
    Required: Name, data type, cardinality (one or many).
    Optional: indexed, unique, and more.
    !
    Datomic does not proscribe
    how you combine attributes on entities!
    

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24. Let’s see some
    code already!
    

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25. We are hiring!
    Pure Clojure, ClojureScript & Datomic
    Experience with other stacks OK!
    !
    robert@cognician.com
    @RobStuttaford
    

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26. Cape Town Clojure User Group
    Meet 1 or 2 Thursday evenings a month
    Next meet: 6-9pm,14 February 2014
    Venue: Codebridge in Claremont
    @clj_ug_ct
    !
    Talk notes: http://is.gd/imm_db
    

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