feat(psql): introduce column type ltree (#604)

* feat: introduce `LTree` column type

* feat: the `ltree` type

src/backend/mysql/table.rs

@@ -105,6 +105,7 @@ impl TableBuilder for MysqlQueryBuilder {
                 ColumnType::Cidr => unimplemented!("Cidr is not available in MySQL."),
                 ColumnType::Inet => unimplemented!("Inet is not available in MySQL."),
                 ColumnType::MacAddr => unimplemented!("MacAddr is not available in MySQL."),
+                ColumnType::LTree => unimplemented!("LTree is not available in MySQL."),
             }
         )
         .unwrap();

src/backend/postgres/table.rs

@@ -77,6 +77,7 @@ impl TableBuilder for PostgresQueryBuilder {
                 ColumnType::Inet => "inet".into(),
                 ColumnType::MacAddr => "macaddr".into(),
                 ColumnType::Year(_) => unimplemented!("Year is not available in Postgres."),
+                ColumnType::LTree => "ltree".into(),
             }
         )
         .unwrap()

src/backend/sqlite/table.rs

@@ -90,6 +90,7 @@ impl TableBuilder for SqliteQueryBuilder {
                 ColumnType::Year(_) => unimplemented!("Year is not available in Sqlite."),
                 ColumnType::Bit(_) => unimplemented!("Bit is not available in Sqlite."),
                 ColumnType::VarBit(_) => unimplemented!("VarBit is not available in Sqlite."),
+                ColumnType::LTree => unimplemented!("LTree is not available in Sqlite."),
             }
         )
         .unwrap()

src/extension/postgres/ltree.rs

@@ -0,0 +1,57 @@
+use std::fmt;
+
+/// PostgreSQL `ltree` extension type.
+///
+/// `ltree` stores a raber path which in this struct is represented as the
+/// tuple's first value.
+///
+/// # PostcreSQL Reference
+///
+/// The following set of SQL statements can be used to create a table with
+/// a `ltree` column. Here the `ltree` column is called `path`.
+///
+/// The `path` column is then populated to generate the tree.
+///
+/// ```ignore
+/// CREATE TABLE test (path ltree);
+/// INSERT INTO test VALUES ('Top');
+/// INSERT INTO test VALUES ('Top.Science');
+/// INSERT INTO test VALUES ('Top.Science.Astronomy');
+/// INSERT INTO test VALUES ('Top.Science.Astronomy.Astrophysics');
+/// INSERT INTO test VALUES ('Top.Science.Astronomy.Cosmology');
+/// INSERT INTO test VALUES ('Top.Hobbies');
+/// INSERT INTO test VALUES ('Top.Hobbies.Amateurs_Astronomy');
+/// INSERT INTO test VALUES ('Top.Collections');
+/// INSERT INTO test VALUES ('Top.Collections.Pictures');
+/// INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy');
+/// INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Stars');
+/// INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Galaxies');
+/// INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Astronauts');
+/// CREATE INDEX path_gist_idx ON test USING GIST (path);
+/// CREATE INDEX path_idx ON test USING BTREE (path);
+/// ```
+///
+/// The set of queries above will generate the following tree:
+///
+/// ```ignore
+///                        Top
+///                     /   |  \
+///              Science Hobbies Collections
+///                /       |              \
+///       Astronomy   Amateurs_Astronomy Pictures
+///            /  \                            |
+/// Astrophysics  Cosmology                Astronomy
+///                                       /    |    \
+///                                Galaxies  Stars  Astronauts
+/// ```
+/// [Source][1]
+///
+/// [1]: https://www.postgresql.org/docs/current/ltree.html
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct PgLTree;
+
+impl fmt::Display for PgLTree {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "ltree")
+    }
+}

src/extension/postgres/mod.rs

@@ -2,6 +2,7 @@ pub use expr::*;
 pub use extension::*;
 pub use func::*;
 pub use interval::*;
+pub use ltree::*;
 pub use types::*;
 
 use crate::types::BinOper;
@@ -10,6 +11,7 @@ pub(crate) mod expr;
 pub(crate) mod extension;
 pub(crate) mod func;
 pub(crate) mod interval;
+pub(crate) mod ltree;
 pub(crate) mod types;
 
 /// Binary operator

src/table/column.rs

@@ -52,6 +52,7 @@ pub enum ColumnType {
     Cidr,
     Inet,
     MacAddr,
+    LTree,
 }
 
 impl PartialEq for ColumnType {
@@ -558,6 +559,13 @@ impl ColumnDef {
         self
     }
 
+    /// Set column type as `ltree`
+    /// This is only supported on Postgres.
+    pub fn ltree(&mut self) -> &mut Self {
+        self.types = Some(ColumnType::LTree);
+        self
+    }
+
     /// Set constraints as SimpleExpr
     ///
     /// ```

tests/mysql/query.rs

@@ -995,8 +995,7 @@ fn select_58() {
             .and_where(Expr::col(Char::Character).like(LikeExpr::new("A").escape('\\')))
             .build(MysqlQueryBuilder),
         (
-            r#"SELECT `character` FROM `character` WHERE `character` LIKE ? ESCAPE '\\'"#
-                .to_owned(),
+            r"SELECT `character` FROM `character` WHERE `character` LIKE ? ESCAPE '\\'".to_owned(),
             Values(vec!["A".into()])
         )
     );

tests/postgres/table.rs

@@ -597,3 +597,27 @@ fn alter_with_check_constraint() {
         r#"ALTER TABLE "glyph" ADD COLUMN "aspect" integer NOT NULL DEFAULT 101 CHECK ("aspect" > 100)"#,
     );
 }
+
+#[test]
+fn create_16() {
+    assert_eq!(
+        Table::create()
+            .table(Glyph::Table)
+            .col(
+                ColumnDef::new(Glyph::Id)
+                    .integer()
+                    .not_null()
+                    .auto_increment()
+                    .primary_key()
+            )
+            .col(ColumnDef::new(Glyph::Tokens).ltree())
+            .to_string(PostgresQueryBuilder),
+        [
+            r#"CREATE TABLE "glyph" ("#,
+            r#""id" serial NOT NULL PRIMARY KEY,"#,
+            r#""tokens" ltree"#,
+            r#")"#,
+        ]
+        .join(" ")
+    );
+}