Add support for the PostgreSQL hstore extension

src/backend/mysql/table.rs

@@ -94,6 +94,7 @@ impl TableBuilder for MysqlQueryBuilder {
                 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."),
+                ColumnType::Hstore => unimplemented!("Hstore is not available in MySQL."),
             }
         )
         .unwrap();

src/backend/postgres/table.rs

@@ -78,6 +78,7 @@ impl TableBuilder for PostgresQueryBuilder {
                 ColumnType::MacAddr => "macaddr".into(),
                 ColumnType::Year => unimplemented!("Year is not available in Postgres."),
                 ColumnType::LTree => "ltree".into(),
+                ColumnType::Hstore => "hstore".into(),
             }
         )
         .unwrap()

src/backend/sqlite/table.rs

@@ -191,6 +191,7 @@ impl SqliteQueryBuilder {
                 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."),
+                ColumnType::Hstore => unimplemented!("Hstore is not available in Sqlite."),
             }
         )
         .unwrap()

src/extension/postgres/hstore.rs

@@ -0,0 +1,45 @@
+use crate::Iden;
+
+/// PostgreSQL `hstore` extension type.
+///
+/// `hstore` provides semi-structured data support by storing key/value pairs in a single column.
+///
+/// See [the Postgres manual, Appendix F, Section 18][PG.F.18]
+///
+/// [PG.F.18]: https://www.postgresql.org/docs/current/hstore.html
+///
+/// ### Note: Requires Postgres 8.3+
+/// The `hstore` extension was first added in PostgreSQL 8.3.
+///
+/// # PostgreSQL Reference
+/// The following set of SQL statements can be used to create a table with a `hstore` column.
+///
+/// ```ignore
+/// create table users (username varchar primary key, password varchar, additional_data hstore);
+/// create index idx_gist on users using gist (additional_data); -- Sets GIST index support.
+/// create index idx_gin on users using gin (additional_data);   -- Sets GIN index support.
+///
+/// insert into users values ('[email protected]', '@super_secret_1', 'department=>IT');
+/// -- additional_data contains department => IT.
+/// update users set additional_data['equipment_issued'] = null where username = '[email protected]';
+/// -- additional_data now contains equipment_issued => null, department => IT.
+///
+/// select * from users;
+/// select * from users where additional_data['department'] = 'IT';
+/// select * from users where additional_data->'department' = 'IT'; -- Alternate form.
+/// ```
+///
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct PgHstore;
+
+impl Iden for PgHstore {
+    fn unquoted(&self, s: &mut dyn std::fmt::Write) {
+        write!(s, "hstore").unwrap();
+    }
+}
+
+impl From<PgHstore> for String {
+    fn from(l: PgHstore) -> Self {
+        l.to_string()
+    }
+}

src/extension/postgres/mod.rs

@@ -1,6 +1,7 @@
 pub use expr::*;
 pub use extension::*;
 pub use func::*;
+pub use hstore::*;
 pub use ltree::*;
 pub use types::*;
 
@@ -9,6 +10,7 @@ use crate::types::BinOper;
 pub(crate) mod expr;
 pub(crate) mod extension;
 pub(crate) mod func;
+pub(crate) mod hstore;
 pub(crate) mod interval;
 pub(crate) mod ltree;
 pub(crate) mod types;

src/table/column.rs

@@ -54,6 +54,7 @@ pub trait IntoColumnDef {
 /// | Inet                  | N/A               | inet                        | N/A                          |
 /// | MacAddr               | N/A               | macaddr                     | N/A                          |
 /// | LTree                 | N/A               | ltree                       | N/A                          |
+/// | Hstore                | N/A               | hstore                      | N/A                          |
 #[non_exhaustive]
 #[derive(Debug, Clone)]
 pub enum ColumnType {
@@ -98,6 +99,7 @@ pub enum ColumnType {
     Inet,
     MacAddr,
     LTree,
+    Hstore,
 }
 
 /// Length for var-char/binary; default to 255
@@ -638,6 +640,37 @@ impl ColumnDef {
         self
     }
 
+    /// Set column type as `hstore`
+    /// This is only supported on Postgres.
+    ///
+    /// ```
+    /// use sea_query::{tests_cfg::*, *};
+    /// assert_eq!(
+    ///     Table::create()
+    ///         .table(Glyph::Table)
+    ///         .col(
+    ///             ColumnDef::new(Glyph::Id)
+    ///                 .integer()
+    ///                 .not_null()
+    ///                 .auto_increment()
+    ///                 .primary_key()
+    ///         )
+    ///         .col(ColumnDef::new(Glyph::Tokens).hstore())
+    ///         .to_string(PostgresQueryBuilder),
+    ///     [
+    ///         r#"CREATE TABLE "glyph" ("#,
+    ///         r#""id" serial NOT NULL PRIMARY KEY,"#,
+    ///         r#""tokens" hstore"#,
+    ///         r#")"#,
+    ///     ]
+    ///     .join(" ")
+    /// );
+    /// ```
+    pub fn hstore(&mut self) -> &mut Self {
+        self.types = Some(ColumnType::Hstore);
+        self
+    }
+
     /// Set constraints as SimpleExpr
     ///
     /// ```