GraphQL

Here is a link to the official documentations. You can learn and get a feel on how can you implement this package which is a GraphQL-to-SQL translator with Persistent package return value processing to make a GraphQL format return object string.

This module is made to enable interpreting your GraphQL queries. The expected query type is a single string to comprise all your GraphQL queries and fragments. Expected variable type is a single string to your variable to value definitions.

When errors are encountered, this module is simply going to throw an uncaught Exception. The Exception name is some hint to where was the error encountered. More information is provided in the below function description.

Not all GraphQL features are currently supported. For a list to updates and current state, you should check the GitHub updates and example page.

Functions

These are available methods to give access to the package interpretation, validation, and formatting features.

processQueryString

Arguments

:: String

GraphQL query argument as String.

-> [(String, [String])]

unique server object name to list of query reference names.

-> [(String, [(String, String)])]

unique server object name to list of valid scalar subfields (which are exactly named after database column names) and the subfield type.

-> [(String, [String])]

unique server object name to list of valid nested object subfields (which are named to your preference, though you must include these in the tuple list in the first argument list)

-> [(String, [String])]

unique server object name to list of database table names (which are exact references to table names).

-> [(String, String, [String])]

two database table names to list of from-to-and intermediate triplet strings as described above to identify all GraphQL relationships with database sequences.

-> ([RootObject], [[String]])

The return value is one tuple with server objects and list with grouped sql query strings.

This is the simplest function to call to get queries from a GraphQL query. Below are methods where schema is given as json file and not argument strings if this is preferred.

Instructions to give server schema arguments:

1. make a list of all server objects in the heirarchy in separate tuples with a list to all pseudonyms (that's including the ones that are referred by relationships)
2. make a list of all above mentioned server objects in separate tuples with a list to all valid scalar subfields as you read them from your database (valid types are Text, ByteString, Int, Double, Rational, Bool, Day, TimeOfDay, or UTCTime)
3. make a list of all above mentioned server objects in separate tuples with a list to all valid nested object subfields as you want them to be named (also include these in the first list)
4. make a list of all above mentioned server objects in separate tuples with a list to all reference database table name(s) as you read them
5. make a list of database table names in separate tuples with another database table name and a list to the SQL database tables that are between the two first tables; the list order is... identity table name (the first String in this tuple), identity leaving-field name, referring table name (the table that's corresponding to the second String in this tuple), referring table entering-field name, and (if present) three String sequences that is intermediary-table name, intermediary-table entering-column name, and intermediary-table leaving-column name. The intermediary tables are ordered from closest to indentity table to closest to referencing table.

To implement server type heirarchy:

• add new tuple to first schema argument,
• add new tuple to second schema argument (where list is the intersection fields on all children),
• add new tuple to third schema argument (where list is the intersection fields on all children),
• and add new tuple to fourth schema argument (where list is all children database tables).

You should not need more cases within fifth schema argument, but you may find a child database table and third schema argument list elements pair that is not included.

You then will need to include this, or error is thrown.

Here is an example of the GraphQL schema arguments that are expected from the last five arguments. We'll use the GitHub example database schema to illustrate the expected arguments.

• The first schema argument (second argument) is a mapping to names to which a server object is possibly referred in any GraphQL query:

      [(Person,[Person,"person","owner"]),(Family,[Family,"family"]),(Genus,[Genus,"genus"]),(Species,[Species,"species"]),(Breed,[Breed,"breed"]),(Pet,[Pet,"pet"]),(Taxonomy,[Taxonomy,"taxonomy"])]
  

• The second schema argument is a mapping to valid scalar subfields and type from every server object that is listed in the first schema argument:

      [(Person,[("id",Int),("name",Text),("gender",Int)]),(Family,[("id",Int),("name",Text)]),(Genus,[("name",Text)]),(Species,[("id",Int),("name",Text)]),(Breed,[("id",Int),("name",Text)]),(Pet,[("id",Int),("name",Text),("gender",Int)]),(Taxonomy,[("name",Text)])]
  

NOTE: You should give only the intersection subfields set to parent server objects with all the children server objects.

NOTE: Valid scalar types are Text, ByteString, Int, Double, Rational, Bool, Day, TimeOfDay, or UTCTime.

• The third schema argument is a mapping to valid nested object (or entity) subfields from every server object that is listed in the first schema argument:

      [(Person,["pet"]),(Family,["genus","species","breed","pet"]),(Genus,["family","species","breed","pet"]),(Species,["family","genus","breed","pet"]),(Breed,["family","genus","species","pet"]),(Pet,["owner","breed","species","genus","family"]),(Taxonomy,["pet"])]
  

NOTE: You should give only the intersection subfields set to parent server objects with all the children server objects.

NOTE: You should also put the list names in the lists in the first argument to map the name to ServerObject.

• The fourth schema argument is a mapping to exact database names (it is maybe helpful to first have the database schema and copy names to this list mapping) for every listed server object in the first schema argument:

      [(Person,["person"]),(Family,["family"]),(Genus,["genus"]),(Species,["species"]),(Breed,["breed"]),(Pet,["pet"]),(Taxonomy,["family","genus","species","breed"])]
  

NOTE: This is where can you introduce type heirarchies and generalizations. The above Taxonomy server object is an example. You can see that it is an encompassing term for all the biological classifications in our database schema.

• The fifth schema argument is a mapping to exact database table names and fields names to link the from-object to the to-object.

Within every tuple,

the first String is the identity database table name (with type heirarchies, you make a separate tuple on every referenced database table if the to-from pair is not already mentioned as explicit pairing).

The second String is the referencing database name.

The third tuple value is a list that is showing the link between our identity table and referring table. The order is first identity database table name, second identity database leaving field name, third referencing database table name, fourth referencing database table arrival field name, and the remainder (if identity table and referencing table are not directly linked) is a triplet of Strings that are ordered from nearest to identity table to closer to referencing table. The triplets are intermediate database table name, intermediate database arrival field, and intermediate database exiting field. Here is an illustration:

      -- Person
      [("person","pet",["person","id","pet","id","pet_ownership","owner_id","animal_id"]),
      ("person","breed",["person","id","breed","id","pet_ownership","owner_id","animal_id","pet","id","id","pet_type","pet_id","breed_id"]),
      ("person","species",["person","id","species","id","pet_ownership","owner_id","animal_id","pet","id","id","pet_type","pet_id","breed_id","breed","id","species_id"]),
      ("person","genus",["person","id","genus","id","pet_ownership","owner_id","animal_id","pet","id","id","pet_type","pet_id","breed_id","breed","id","species_id","species","id","genus_id"]),
      ("person","family",["person","id","family","id","pet_ownership","owner_id","animal_id","pet","id","id","pet_type","pet_id","breed_id","breed","id","species_id","species","id","genus_id","genus","id","family_id"]),
      -- Family
      ("family","pet",["family","id","pet","id","genus","family_id","id","species","genus_id","id","breed","species_id","id","pet_type","breed_id","pet_id"]),
      ("family","genus",["family","id","genus","family_id"]),
      ("family","species",["family","id","species","genus_id","genus","family_id","id"]),
      ("family","breed",["family","id","breed","species_id","genus","family_id","id","species","genus_id","id"]),
      -- Genus
      ("genus","pet",["genus","id","pet","id","species","genus_id","id","breed","species_id","id","pet_type","breed_id","pet_id"]),
      ("genus","family",["genus","family_id","family","id"]),
      ("genus","species",["genus","id","species","genus_id"]),
      ("genus","breed",["genus","id","breed","species_id","species","genus_id","id"]),
      -- Species
      ("species","pet",["species","id","pet","id","breed","species_id","id","pet_type","breed_id","pet_id"]),
      ("species","breed",["species","id","breed","species_id"]),
      ("species","genus",["species","genus_id","genus","id"]),
      ("species","family",["species","id","family","genus_id","genus","species_id","id"]),
      -- Breed
      ("breed","pet",["breed","id","pet","id","pet_type","breed_id","pet_id"]),
      ("breed","species",["breed","species_id","species","id"]),
      ("breed","genus",["breed","species_id","genus","id","species","id","genus_id"]),
      ("breed","family",["breed","species_id","family","id","species","id","genus_id","genus","id","family_id"]),
      -- Pet
      ("pet","person",["pet","id","person","id","pet_ownership","animal_id","owner_id"]),
      ("pet","breed",["pet","id","breed","id","pet_type","pet_id","breed_id"]),
      ("pet","species",["pet","id","species","id","pet_type","pet_id","breed_id","breed","id","species_id"]),
      ("pet","genus",["pet","id","genus","id","pet_type","pet_id","breed_id","breed","id","genus_id"]),
      ("pet","family",["pet","id","family","id","pet_type","pet_id","breed_id","breed","id","genus_id","genus","id","family_id"])]
  

When an error is encountered, an uncaught exception is thrown. Exceptions thrown by this function are:

• SyntaxException (when there is a problem with the given GraphQL query syntax)
• ParseFragmentException (when there is a problem with a Fragment syntax)
• EmptyQueryException (when the query is left blank)
• InvalidObjectException (when there is problem in nested object syntax, an object is not recognized, or server data is misinterpreted)
• InvalidObjectSubFieldException (when a subfield is requested from nested object that is not having ownership of the subfield)
• InvalidScalarException (when there is syntax error in listing scalar fields, or server data is misinterpreted)
• NullArgumentException (when a transformation is set but no argument is given though we do not yet support transformations)
• CreatingSqlQueryObjectFieldsException (when there are too many nested object subfields than nested objects to hold them or when there is a problem with the aligning of server object relationship argument - that's the fifth schema argument)
• RelationshipConfigurationException (when the relationship schema fifth arugment is incorrect number of String values or when an unrecognized pairing is found)
• FailedObjectEqualityException (when we could not match identical queries)
• DuplicateRootObjectsException (when there is an overlapping query)

As a final note, we turn our attention to what is posted on the official GraphQL docs:

"In contrast, GraphQL only returns the data that's explicitly requested, so new capabilities can be added via new types and new fields on those types without creating a breaking change. This has lead to a common practice of always avoiding breaking changes and serving a versionless API." - https://graphql.github.io/learn/best-practices/

With respect to that, you should be sure to be explicit with your here representation on your data schema. You should give all planned details, and you should make adjustments when you feel to evolve your server with your desired schema.

processQueryStringWithVariables

Arguments

:: String

This is the GraphQL query

-> String

This is the variables string

-> [(String, [String])]

unique server object name to list of query reference names.

-> [(String, [(String, String)])]

unique server object name to list of valid scalar subfields (which are exactly named after database column names) and the subfield type.

-> [(String, [String])]

unique server object name to list of valid nested object subfields (which are named to your preference, though you must include these in the tuple list in the first argument list)

-> [(String, [String])]

unique server object name to list of database table names (which are exact references to table names).

-> [(String, String, [String])]

two database table names to list of from-to-and intermediate triplet strings as described above to identify all GraphQL relationships with database sequences.

-> ([RootObject], [[String]])

The return value is one tuple with server objects and list with grouped sql query strings.

This method is same as above, but another second argument is a string to give variables in your query.

The expected variables string is json syntax.

When you declare variable types at the beginning of the query, valid types are Text, ByteString, Int, Double, Rational, Bool, Day, TimeOfDay, or UTCTime.

There are additional thrown exceptions:

• MissingVariableValueException (when we are missing variables in the variables-value string to the query)
• InvalidVariableNameException (when we cannot find a variable in the query with given variables-value string)
• MismatchedVariableTypeException (when query variable type is not matching object scalar type)
• InvalidVariableTypeException (when variable type is invalid or missing)
• ReadVariablesException (when the variables json string syntax is incorrect or was not correctly read)
• VariablesSyntaxException (when the query variables declaration is invalid syntax)

NOTE: the variable-value json string is variable names without $ at the beginning while all other calls are with preceding $.

processQueryStringWithJson

Arguments

:: MonadIO m

=> String

This is the GraphQL query

-> FilePath

This is the filepath to your server schema json file

-> m ([RootObject], [[String]])

The return value is a monad of one tuple with server objects and list with grouped sql query strings.

Except being nested in a monad, this funcion is same as above.

It is allowing you to use a json file to declare your server data schema.

The json format is a list of objects. You detail your schema with a list of objects to refer to server objects...

Instructions to give server schema:

The every object is...

1. "servername" is a string to name the server object
2. "pseudonyms" is a list of string to give all query reference
3. "scalarfields" is a list of objects that are scalar name under "name" and scalar type under "type"
4. "objectfields" is a list of nested object fields
5. "databasetables" is a list of tables in your database
6. "databaserelationships" is a list of database relationships from this refering table to another table

NOTE: You do not need to repeat databaserelationships in any objects. A relationship is given once, and more is redundant...

NOTE: You should put every objectfields value in some pseudonym list value.

Here is an example:

     [
       {
         "servername": Person,
         "pseudonyms": [
           "person",
           Person,
           "owner"
         ],
         "scalarfields": [
           {
             "name": "id",
             "type": Int
           },
           {
             "name": "name",
             "type": Text
           },
           {
             "name": "gender",
             "type": Int
           }
         ],
         "objectfields": [
           "pet"
         ],
         "databasetables": [
           "person"
         ],
         "databaserelationships": [
           ["person","id","pet","id","pet_ownership","owner_id","animal_id"]
         ]
       },
       {
         "servername": Pet,
         "pseudonyms": [
           "pet",
           Pet
         ],
         "scalarfields": [
           {
             "name": "id",
             "type": Int
           },
           {
             "name": "name",
             "type": Text
           },
           {
             "name": "gender",
             "type": Int
           }
         ],
         "objectfields": [
           "owner"
         ],
         "databasetables": [
           "pet"
         ],
         "databaserelationships": [
           ["pet","id","person","id","pet_ownership","animal_id","owner_id"]
         ]
       }
     ]
    

To implement server type heirarchy:

• add new object to list,
• give the children intersection scalar fields in the scalarfields argument,
• give the children intersection object fields in the objectfields argument,
• and add all referring children database table names to the databasetables argument.

You should not need more cases in the databaserelationships argument, but you may find a child database table and object field database table pair that is not included.

The exceptions thrown with this function are same as above function processQueryString, but there are a few more...

• ImportSchemaException (when there is a problem with reading your schema)
• ImportSchemaServerNameException (when there is a problem with reading your servername argument)
• ImportSchemaPseudonymsException (when there is a problem with reading your pseudonyms list argument)
• ImportSchemaScalarFieldsException (when there is a problem with reading your scalarfields list argument)
• ImportSchemaObjectFieldsException (when there is a problem with reading your objectfields list argument)
• ImportSchemaDatabaseTablesException (when there is a problem with reading your databasetables list argument)
• ImportSchemaDatabaseRelationshipsException (when there is a problem with reading your databaserelationships list argument)

As a final note, we turn our attention to what is posted on the official GraphQL docs:

"In contrast, GraphQL only returns the data that's explicitly requested, so new capabilities can be added via new types and new fields on those types without creating a breaking change. This has lead to a common practice of always avoiding breaking changes and serving a versionless API." - https://graphql.github.io/learn/best-practices/

With respect to that, you should be sure to be explicit with your here representation on your data schema. You should give all planned details, and you should make adjustments when you feel to evolve your server with your desired schema.

processQueryStringWithJsonAndVariables

Arguments

:: MonadIO m

=> String

This is the GraphQL query

-> String

This is the variables string

-> FilePath

This is the filepath to your server schema json file

-> m ([RootObject], [[String]])

The return value is a monad of one tuple with server objects and list with grouped sql query strings.

This method is same as above, but another third argument is a string to give variables in your query.

The expected variables string is json syntax.

When you declare variable types at the beginning of the query, valid types are Text, ByteString, Int, Double, Rational, Bool, Day, TimeOfDay, or UTCTime.

There are additional thrown exceptions:

• MissingVariableValueException (when we are missing variables in the variables-value string to the query)
• InvalidVariableNameException (when we cannot find a variable in the query with given variables-value string)
• MismatchedVariableTypeException (when query variable type is not matching object scalar type)
• InvalidVariableTypeException (when variable type is invalid or missing)
• ReadVariablesException (when the variables json string syntax is incorrect or was not correctly read)
• VariablesSyntaxException (when the query variables declaration is invalid syntax)

NOTE: the variable-value json string is variable names without $ at the beginning while all other calls are with preceding $.

processPersistentData

Arguments

:: [(String, [(String, String)])]

unique server object name to list of valid scalar subfields (which are exactly named after database column names) and the subfield type.

-> [[[[Text]]]]

database query return value as casted to only Text data types and with no other alterations (a list of GraphQL-grouped results list of SQL query results list of data row lists)

-> [RootObject]

unmodified server objects that was given by the previous processQueryString function.

-> String

The return value is a string type to describe the GraphQL-organized return values.

This is the function to call after casting PersistValues to Text from processQueryString of which you may find on my examples page.

The ordered arguments are:

• all the data that is cast to Text type
• an unmodified copy of the RootObject list that is returned from processing the query string.

The return result is a string to resemble the GraphQL return value.

Current implementation is to cast all values to Text since arbitrary columns data types are not inferred, though next update is changing this limitation.

When an error is encountered, an uncaught exception is thrown. The exceptions thrown are of:

• InvalidObjectException (when server data is misinterpreted or an unrecognized server object is met)
• InvalidScalarException (when server data is misinterpreted)
• EOFDataProcessingException (when the given data is shorter than expected in reference to the given serve objects)
• InvalidArgumentException (when there is an internal argument error - you should not observe this)
• InvalidVariableTypeException (when an unrecognized base data type is met)
• InvalidObjectScalarFieldException (when an unrecognized object-scalar pair is met)

processPersistentDataWithJson

Arguments

:: MonadIO m

=> FilePath

This is the file path to schema json

-> [[[[Text]]]]

This is the unmodified Persistent database query return value (a list of GraphQL-grouped results list of SQL query results list of data row lists).

-> [RootObject]

This is the unmodified server objects that was composed from previous processQueryString function.

-> m String

The return value is a monad of string type to describe the GraphQL-organized return values.

This is a json version from the above function. It is also wrapped in a monad

The exceptions thrown with this function are same as above function, but there are a few more...

• ImportSchemaException (when there is a problem with reading your schema)
• ImportSchemaServerNameException (when there is a problem with reading your servername argument)
• ImportSchemaPseudonymsException (when there is a problem with reading your pseudonyms list argument)
• ImportSchemaScalarFieldsException (when there is a problem with reading your scalarfields list argument)
• ImportSchemaObjectFieldsException (when there is a problem with reading your objectfields list argument)
• ImportSchemaDatabaseTablesException (when there is a problem with reading your databasetables list argument)
• ImportSchemaDatabaseRelationshipsException (when there is a problem with reading your databaserelationships list argument)

Server data types

These are server data types that are return from processQueryString. You do not need to know these to know how is this package used, but you'll get some insight to what is used to store and organize your GraphQL data.

type RootObjects = [RootObject]

These are objects to represent GraphQL query roots.

type RootObject = NestedObject

data NestedObject

NestedObjects are the general object type. They are found as RootObjects or as object Subfields.

Constructors

NestedObject Alias Name ServerObject SubSelection SubFields

Instances

Show NestedObject

Defined in Model.ServerObjectTypes

Methods

showsPrec :: Int -> NestedObject -> ShowS

show :: NestedObject -> String

showList :: [NestedObject] -> ShowS

type Alias = Maybe String

type ServerObject = String

type SubSelection = Maybe ScalarType

type SubFields = [Field]

type Field = Either ScalarType NestedObject

data ScalarType

ScalarTypes are the other subfield type. They are also found at object attributes.

Constructors

ScalarType Alias Name Transformation Argument

Instances

Eq ScalarType

Defined in Model.ServerObjectTypes

Methods

(==) :: ScalarType -> ScalarType -> Bool

(/=) :: ScalarType -> ScalarType -> Bool

Show ScalarType

Defined in Model.ServerObjectTypes

Methods

showsPrec :: Int -> ScalarType -> ShowS

show :: ScalarType -> String

showList :: [ScalarType] -> ShowS

type Transformation = Maybe String

type Argument = Maybe String

type Name = String

Server exceptions

These are server exceptions to make error handling.

data QueryException

Constructors

SyntaxException

VariableException

ParseFragmentException

EmptyQueryException

InvalidObjectException

InvalidScalarException

InvalidObjectNestedObjectFieldException

InvalidObjectScalarFieldException

InvalidObjectSubFieldException

InvalidAttributeTransformation

NullArgumentException

CreatingSqlQueryObjectFieldsException

CreatingSqlQueryObjectsException

TooManyTablesException

EmptyRowException

EOFDataProcessingException

InvalidArgumentException

Foundlinebreakexception

RelationshipConfigurationException

FailedObjectEqualityException

DuplicateRootObjectsException

ImportSchemaException

ImportSchemaServerNameException

ImportSchemaPseudonymsException

ImportSchemaScalarFieldsException

ImportSchemaObjectFieldsException

ImportSchemaDatabaseTablesException

ImportSchemaDatabaseRelationshipsException

MissingVariableValueException

InvalidVariableNameException

MismatchedVariableTypeException

InvalidVariableTypeException

ReadVariablesException

VariablesSyntaxException

ValueInterpretationException

Instances

Show QueryException

Defined in Model.ServerExceptions

Methods

showsPrec :: Int -> QueryException -> ShowS

show :: QueryException -> String

showList :: [QueryException] -> ShowS

Exception QueryException

Defined in Model.ServerExceptions

Methods

toException :: QueryException -> SomeException

fromException :: SomeException -> Maybe QueryException

displayException :: QueryException -> String