create if not exists

squeal-postgresql/src/Squeal/PostgreSQL/Definition.hs

@@ -184,7 +184,7 @@ createSchema sch = UnsafeDefinition $
 createSchemaIfNotExists
   :: (KnownSymbol sch, Has sch schemas schema)
   => Alias sch
-  -> Definition schemas schemas
+  -> Definition schemas (CreateIfNotExists sch '[] schemas)
 createSchemaIfNotExists sch = UnsafeDefinition $
   "CREATE" <+> "SCHEMA" <+> "IF" <+> "NOT" <+> "EXISTS"
   <+> renderSQL sch <> ";"
@@ -248,16 +248,19 @@ in printSQL setup
 CREATE TABLE IF NOT EXISTS "tab" ("a" int NULL, "b" real NULL);
 -}
 createTableIfNotExists
-  :: ( Has sch schemas schema
-     , Has tab schema ('Table (constraints :=> columns))
+  :: ( KnownSymbol sch
+     , KnownSymbol tab
+     , columns ~ (col ': cols)
      , SOP.SListI columns
-     , SOP.SListI constraints )
+     , SOP.SListI constraints
+     , Has sch schemas0 schema0
+     , schemas1 ~ Alter sch (CreateIfNotExists tab ('Table (constraints :=> columns)) schema0) schemas0 )
   => QualifiedAlias sch tab -- ^ the name of the table to add
-  -> NP (Aliased (ColumnTypeExpression schemas)) columns
+  -> NP (Aliased (ColumnTypeExpression schemas0)) columns
     -- ^ the names and datatype of each column
-  -> NP (Aliased (TableConstraintExpression sch tab schemas)) constraints
+  -> NP (Aliased (TableConstraintExpression sch tab schemas1)) constraints
     -- ^ constraints that must hold for the table
-  -> Definition schemas schemas
+  -> Definition schemas0 schemas1
 createTableIfNotExists tab columns constraints = UnsafeDefinition $
   "CREATE TABLE IF NOT EXISTS"
   <+> renderCreation tab columns constraints

squeal-postgresql/src/Squeal/PostgreSQL/Schema.hs

@@ -60,6 +60,7 @@ module Squeal.PostgreSQL.Schema
   , PGlabel (..)
     -- * Data Definitions
   , Create
+  , CreateIfNotExists
   , Drop
   , Alter
   , Rename
@@ -325,6 +326,11 @@ type family Create alias x xs where
     ':<>: 'Text "already in use")
   Create alias y (x ': xs) = x ': Create alias y xs
 
+type family CreateIfNotExists alias x xs where
+  CreateIfNotExists alias x '[] = '[alias ::: x]
+  CreateIfNotExists alias x (alias ::: y ': xs) = (alias ::: y ': xs)
+  CreateIfNotExists alias y (x ': xs) = x ': Create alias y xs
+
 -- | @Drop alias xs@ removes the type associated with @alias@ in @xs@
 -- and is used in `Squeal.PostgreSQL.Definition.dropTable` statements
 -- and in @ALTER TABLE@ `Squeal.PostgreSQL.Definition.dropColumn` statements.