Safe Haskell	Safe-Inferred
Language	Haskell2010

Hasura.Backends.Postgres.Execute.Prepare

Description

Postgres Execute Prepare

Deals with translating (session) variables to SQL expressions. Uses a state monad to keep track of things like variables and generating fresh variable names.

See Execute.

Synopsis

type PlanVariables = HashMap PlanVariable Int
type PrepArgMap = IntMap (PrepArg, PGScalarValue)
data PlanningSt = PlanningSt {
- _psArgNumber :: Int
- _psVariables :: PlanVariables
- _psPrepped :: PrepArgMap
}
initPlanningSt :: PlanningSt
prepareWithPlan :: (MonadState PlanningSt m, MonadError QErr m) => UserInfo -> UnpreparedValue ('Postgres pgKind) -> m SQLExp
prepareWithoutPlan :: MonadError QErr m => UserInfo -> UnpreparedValue ('Postgres pgKind) -> m SQLExp
withUserVars :: SessionVariables -> PrepArgMap -> PrepArgMap

Documentation

type PlanVariables = HashMap PlanVariable Int Source #

type PrepArgMap = IntMap (PrepArg, PGScalarValue) Source #

The value is (PG.PrepArg, PGScalarValue) because we want to log the human-readable value of the prepared argument and not the binary encoding in PG format

data PlanningSt Source #

Constructors

PlanningSt
Fields _psArgNumber :: Int _psVariables :: PlanVariables _psPrepped :: PrepArgMap

Instances

Instances details

Show PlanningSt Source #
Instance details Defined in Hasura.Backends.Postgres.Execute.Prepare Methods showsPrec :: Int -> PlanningSt -> ShowS # show :: PlanningSt -> String # showList :: [PlanningSt] -> ShowS #
Eq PlanningSt Source #
Instance details Defined in Hasura.Backends.Postgres.Execute.Prepare Methods (==) :: PlanningSt -> PlanningSt -> Bool # (/=) :: PlanningSt -> PlanningSt -> Bool #

initPlanningSt :: PlanningSt Source #

prepareWithPlan :: (MonadState PlanningSt m, MonadError QErr m) => UserInfo -> UnpreparedValue ('Postgres pgKind) -> m SQLExp Source #

If we're preparing a value with planning state, we favour referring to values by their prepared argument index. If the value refers to a session value, we look for it in prepared value (1) and access the particular keys using the JSONB ->> accessor.

prepareWithoutPlan :: MonadError QErr m => UserInfo -> UnpreparedValue ('Postgres pgKind) -> m SQLExp Source #

If we're not using a prepared statement, substitution is pretty naïve: we resolve session variable names, ignore parameter names, and substitute into the SQLExp.

withUserVars :: SessionVariables -> PrepArgMap -> PrepArgMap Source #

The map of user session variables is always given the number (1) as its variable argument number (see getVarArgNum). If we want to refer to a particular variable in this map, we use JSONB functions to interrogate variable (1).