chore: add extensions to schema cache

crates/pgt_schema_cache/src/extensions.rs

@@ -0,0 +1,22 @@
+use sqlx::PgPool;
+
+use crate::schema_cache::SchemaCacheItem;
+
+#[derive(Debug, Default)]
+pub struct Extension {
+    pub name: String,
+    pub schema: Option<String>,
+    pub default_version: String,
+    pub installed_version: Option<String>,
+    pub comment: Option<String>,
+}
+
+impl SchemaCacheItem for Extension {
+    type Item = Extension;
+
+    async fn load(pool: &PgPool) -> Result<Vec<Extension>, sqlx::Error> {
+        sqlx::query_file_as!(Extension, "src/queries/extensions.sql")
+            .fetch_all(pool)
+            .await
+    }
+}

crates/pgt_schema_cache/src/lib.rs

@@ -3,6 +3,7 @@
 #![allow(dead_code)]
 
 mod columns;
+mod extensions;
 mod functions;
 mod policies;
 mod roles;
@@ -14,6 +15,7 @@ mod types;
 mod versions;
 
 pub use columns::*;
+pub use extensions::Extension;
 pub use functions::{Behavior, Function, FunctionArg, FunctionArgs, ProcKind};
 pub use policies::{Policy, PolicyCommand};
 pub use roles::*;

crates/pgt_schema_cache/src/queries/extensions.sql

@@ -0,0 +1,10 @@
+SELECT
+  e.name as "name!",
+  n.nspname AS schema,
+  e.default_version as "default_version!",
+  x.extversion AS installed_version,
+  e.comment
+FROM
+  pg_available_extensions() e(name, default_version, comment)
+  LEFT JOIN pg_extension x ON e.name = x.extname
+  LEFT JOIN pg_namespace n ON x.extnamespace = n.oid

crates/pgt_schema_cache/src/schema_cache.rs

@@ -49,14 +49,6 @@ impl SchemaCache {
         })
     }
 
-    /// Applies an AST node to the repository
-    ///
-    /// For example, alter table add column will add the column to the table if it does not exist
-    /// yet
-    pub fn mutate(&mut self) {
-        unimplemented!();
-    }
-
     pub fn find_table(&self, name: &str, schema: Option<&str>) -> Option<&Table> {
         self.tables
             .iter()