Safe Haskell	None

Database.Neo4j.Transactional.Cypher

Contents

Types
Sending queries
Aux functions

Description

Module to provide Cypher support using the transactional endpoint.

Example:

 import qualified Database.Neo4j.Transactional.Cypher as T

 withConnection host port $ do
    ...
    res <- TC.runTransaction $ do
            -- Queries return a result with columns, rows, a list of graphs and stats
            result <- T.cypher "CREATE (pere: PERSON {age: {age}}) CREATE (pau: PERSON {props}) \
                              \CREATE p1 = (pere)-[:KNOWS]->(pau) RETURN pere, pau, p1, pere.age" $
                                M.fromList [("age", TC.newparam (78 :: Int64)),
                                            ("props", TC.ParamProperties $ M.fromList["age" |: (99 :: Int64)])]
            -- if any of the commands returns an error the transaction is rollbacked and leaves
            result 2 <- T.cypher "not a command" M.empty
            void $ TC.cypher "CREATE (pep: PERSON {age: 55})" M.empty
            -- Transactions are implicitly commited/rollbacked (in case of exception)
            -- but can be explicitly committed and rollbacked
            return (result, result2)

Synopsis

Types

data Result Source

Type for a Cypher response with tuples containing column name and their values

Constructors

Result
Fields cols :: [Text] vals :: [[Value]] graph :: [Graph] stats :: Stats

Instances

Eq Result
Show Result
FromJSON Result	How to create a response object from a cypher JSON response

data Stats Source

Holds the connection stats

Constructors

Stats
Fields containsUpdates :: Bool nodesCreated :: Integer nodesDeleted :: Integer propsSet :: Integer relsCreated :: Integer relsDeleted :: Integer lblsAdded :: Integer lblsRemoved :: Integer idxAdded :: Integer idxRemoved :: Integer constAdded :: Integer constRemoved :: Integer

Instances

Eq Stats
Show Stats
FromJSON Stats	Instance to parse stats from a JSON

data ParamValue Source

Value for a cypher parmeter value, might be a literal, a property map or a list of property maps

Constructors

ParamLiteral PropertyValue
ParamProperties Properties
ParamPropertiesArray [Properties]

Instances

Eq ParamValue
Show ParamValue
ToJSON ParamValue	Instance toJSON for param values so we can serialize them in queries

type Params = HashMap Text ParamValue Source

We use hashmaps to represent Cypher parameters

newparam :: PropertyValueConstructor a => a -> ParamValue Source

emptyStats :: Stats Source

Default stats

type TransError = (Text, Text)Source

Error code and message for a transaction error

Sending queries

loneQuery :: Text -> Params -> Neo4j (Either TransError Result)Source

runTransaction :: Transaction a -> Neo4j (Either TransError a)Source

Run a transaction and get its final result, has an implicit commit request (or rollback if an exception occurred). This implicit commit/rollback will only be executed if it hasn't before because of an explicit one

cypher :: Text -> Params -> Transaction Result Source

Run a cypher query in a transaction, if an error occurs the transaction will stop and rollback

rollback :: Transaction ()Source

Rollback a transaction. After this, executing rollback, commit, keepalive, cypher in the transaction will result in an exception

commit :: Transaction ()Source

Commit a transaction. After this, executing rollback, commit, keepalive, cypher in the transaction will result in an exception

keepalive :: Transaction ()Source

Send a keep alive message to an open transaction

commitWith :: Text -> Params -> Transaction Result Source

Send a cypher query and commit at the same time, if an error occurs the transaction will be rolled back. After this, executing rollback, commit, keepalive, cypher in the transaction will result in an exception

Aux functions

isSuccess :: Either TransError Result -> BoolSource

True if the operation succeeded

fromResult :: Result -> Either TransError Result -> Result Source

Get the result of the response or a default value

fromSuccess :: Either TransError Result -> Result Source

Get the result of the response or a default value