alter if exists

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

@@ -35,7 +35,9 @@ module Squeal.PostgreSQL.Definition.Table
   , dropTable
   , dropTableIfExists
   , alterTable
+  , alterTableIfExists
   , alterTableRename
+  , alterTableIfExistsRename
   , AlterTable (..)
   , addConstraint
   , dropConstraint
@@ -202,16 +204,28 @@ dropTableIfExists tab = UnsafeDefinition $ "DROP TABLE IF EXISTS" <+> renderSQL
 
 -- | `alterTable` changes the definition of a table from the schema.
 alterTable
-  :: (Has sch schemas schema, Has tab schema ('Table table0))
+  :: (Has sch schemas schema, KnownSymbol tab)
   => QualifiedAlias sch tab -- ^ table to alter
-  -> AlterTable sch tab schemas table1 -- ^ alteration to perform
-  -> Definition schemas (Alter sch (Alter tab ('Table table1) schema) schemas)
+  -> AlterTable sch tab schemas table -- ^ alteration to perform
+  -> Definition schemas (Alter sch (Alter tab ('Table table) schema) schemas)
 alterTable tab alteration = UnsafeDefinition $
   "ALTER TABLE"
   <+> renderSQL tab
   <+> renderAlterTable alteration
   <> ";"
 
+-- | `alterTable` changes the definition of a table from the schema.
+alterTableIfExists
+  :: (Has sch schemas schema, KnownSymbol tab)
+  => QualifiedAlias sch tab -- ^ table to alter
+  -> AlterTable sch tab schemas table -- ^ alteration to perform
+  -> Definition schemas (Alter sch (AlterIfExists tab ('Table table) schema) schemas)
+alterTableIfExists tab alteration = UnsafeDefinition $
+  "ALTER TABLE IF EXISTS"
+  <+> renderSQL tab
+  <+> renderAlterTable alteration
+  <> ";"
+
 -- | `alterTableRename` changes the name of a table from the schema.
 --
 -- >>> printSQL $ alterTableRename #foo #bar
@@ -225,6 +239,15 @@ alterTableRename tab0 tab1 = UnsafeDefinition $
   "ALTER TABLE" <+> renderSQL tab0
   <+> "RENAME TO" <+> renderSQL tab1 <> ";"
 
+alterTableIfExistsRename
+  :: (KnownSymbol tab0, KnownSymbol tab1)
+  => Alias tab0 -- ^ table to rename
+  -> Alias tab1 -- ^ what to rename it
+  -> Definition schema (RenameIfExists tab0 tab1 schema)
+alterTableIfExistsRename tab0 tab1 = UnsafeDefinition $
+  "ALTER TABLE IF EXISTS" <+> renderSQL tab0
+  <+> "RENAME TO" <+> renderSQL tab1 <> ";"
+
 -- | An `AlterTable` describes the alteration to perform on the columns
 -- of a table.
 newtype AlterTable

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

@@ -69,7 +69,9 @@ module Squeal.PostgreSQL.Schema
   , DropIfExists
   , DropSchemumIfExists
   , Alter
+  , AlterIfExists
   , Rename
+  , RenameIfExists
   , ConstraintInvolves
   , DropIfConstraintsInvolve
   , IsNotElem
@@ -396,16 +398,34 @@ type family DropSchemumIfExists alias sch xs where
 -- with the type @x@ and is used in `Squeal.PostgreSQL.Definition.alterTable`
 -- and `Squeal.PostgreSQL.Definition.alterColumn`.
 type family Alter alias x xs where
+  Alter alias x '[] = TypeError
+    ('Text "Alter: alias "
+    ':<>: 'ShowType alias
+    ':<>: 'Text " does not exist" )
   Alter alias x1 (alias ::: x0 ': xs) = alias ::: x1 ': xs
   Alter alias x1 (x0 ': xs) = x0 ': Alter alias x1 xs
 
+type family AlterIfExists alias x xs where
+  AlterIfExists alias x '[] = '[]
+  AlterIfExists alias x1 (alias ::: x0 ': xs) = alias ::: x1 ': xs
+  AlterIfExists alias x1 (x0 ': xs) = x0 ': AlterIfExists alias x1 xs
+
 -- | @Rename alias0 alias1 xs@ replaces the alias @alias0@ by @alias1@ in @xs@
 -- and is used in `Squeal.PostgreSQL.Definition.alterTableRename` and
 -- `Squeal.PostgreSQL.Definition.renameColumn`.
 type family Rename alias0 alias1 xs where
+  Rename alias0 alias1 '[] = TypeError
+    ('Text "Rename: alias "
+    ':<>: 'ShowType alias0
+    ':<>: 'Text " does not exist" )
   Rename alias0 alias1 ((alias0 ::: x0) ': xs) = (alias1 ::: x0) ': xs
   Rename alias0 alias1 (x ': xs) = x ': Rename alias0 alias1 xs
 
+type family RenameIfExists alias0 alias1 xs where
+  RenameIfExists alias x '[] = '[]
+  RenameIfExists alias0 alias1 ((alias0 ::: x0) ': xs) = (alias1 ::: x0) ': xs
+  RenameIfExists alias0 alias1 (x ': xs) = x ': RenameIfExists alias0 alias1 xs
+
 -- | Check if a `TableConstraint` involves a column
 type family ConstraintInvolves column constraint where
   ConstraintInvolves column ('Check columns) = column `Elem` columns