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.

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 of updates and current state, you should check the GitHub updates and example page.

Instructions to make server schema:

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
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.

These lists are later used as arguments in a query parsing function.

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.

Then, you will need to include this, or error is thrown.

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 as much detail as possible (sorry for the bad pun), and you should make adjustments when you feel to evolve your server with your desired schema.

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])]

Server object name to list of query reference names.

-> [(String, [String])]

Server object name to list of valid scalar subfields (which are exactly named after database column names).

-> [(String, [String])]

Server object name to list of valid nested object subfields (which are named as pleased, though you must include these in the tuple list in the first argument list)

-> [(String, [String])]

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 of grouped sql query strings.

This is the function to call to get queries from a GraphQL query.

The ordered arguments are:

• the GraphQL query as a string
• a list of tuple of String and list of String that is unique server object names and all names that are referencing them with any query
• a list of tuple of String and list of String that is exact same unique server object names while the list is the valid server object scalar subfields as they are spelt in the database
• a list of tuple of String and list of String that is exact same unique server object names while the list is the valid server object nested object subfields as you want them named and as they are listed in first schema argument
• a list of tuple of String, String, and list of String that is database table name to make an identity name, a reference database table name, and a list of String that is identity table, escape identity column name, reference table, arrival reference column name, and a from-to order of intermediate table triplet strings of intermediate table name, intermediate table arrival column name, and intermediate table departure column name

The return value is a tuple of server representation objects and a list of sql queries. The first list is holding lists that are grouping queries from the same GraphQL query. The inner list is holding the String value sql queries. The server representation objects is later used to format database results to the GraphQL return value syntax.

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 from every server object that is listed in the first schema argument:

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

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

• 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)

processQueryStringWithJson

Arguments

:: MonadIO m

=> String

This is the GraphQL query

-> FilePath

This is the filepath to your server schema json file

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

Return value is same as above, but it is nested in a Monad

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

It is provided a convenience to use json file to configure your schema.

The json format is a list of objects. We're allowing you to here detail your schema with a list of objects to refer to server objects...

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 scalar type fields
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...

Here is an example:

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

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)

processPersistentData

Arguments

:: [[[[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.

The ordered arguments are:

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

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

Making the first argument is demonstrated in the GitHub example.

Current implementation is to cast all values to Text since arbitrary columns data types are not inferred.

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

• InvalidObjectException (when server data is misinterpreted)
• 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)

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