From f35c5f3664005983f9732efc141c0e92a5874b2d Mon Sep 17 00:00:00 2001
From: Harshit Joshi <harshit.j@greedygame.com>
Date: Mon, 26 Aug 2024 23:47:09 +0530
Subject: [PATCH] adds postgres version to the schema cache.

---
 crates/pg_schema_cache/src/lib.rs          |  1 +
 crates/pg_schema_cache/src/schema_cache.rs |  8 +++-
 crates/pg_schema_cache/src/versions.rs     | 43 ++++++++++++++++++++++
 3 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 crates/pg_schema_cache/src/versions.rs

diff --git a/crates/pg_schema_cache/src/lib.rs b/crates/pg_schema_cache/src/lib.rs
index f1e020a5..aed612c6 100644
--- a/crates/pg_schema_cache/src/lib.rs
+++ b/crates/pg_schema_cache/src/lib.rs
@@ -4,6 +4,7 @@
 #![feature(future_join)]
 
 mod functions;
+mod versions;
 mod schema_cache;
 mod schemas;
 mod tables;
diff --git a/crates/pg_schema_cache/src/schema_cache.rs b/crates/pg_schema_cache/src/schema_cache.rs
index 639393a2..cf17697c 100644
--- a/crates/pg_schema_cache/src/schema_cache.rs
+++ b/crates/pg_schema_cache/src/schema_cache.rs
@@ -6,6 +6,7 @@ use crate::functions::Function;
 use crate::schemas::Schema;
 use crate::tables::Table;
 use crate::types::PostgresType;
+use crate::versions::Version;
 
 #[derive(Debug, Clone, Default)]
 pub struct SchemaCache {
@@ -13,6 +14,7 @@ pub struct SchemaCache {
     pub tables: Vec<Table>,
     pub functions: Vec<Function>,
     pub types: Vec<PostgresType>,
+    pub versions: Vec<Version>,
 }
 
 impl SchemaCache {
@@ -21,11 +23,12 @@ impl SchemaCache {
     }
 
     pub async fn load(pool: &PgPool) -> SchemaCache {
-        let (schemas, tables, functions, types) = join!(
+        let (schemas, tables, functions, types, versions) = join!(
             Schema::load(pool),
             Table::load(pool),
             Function::load(pool),
-            PostgresType::load(pool)
+            PostgresType::load(pool),
+            Version::load(pool),
         )
         .await;
 
@@ -34,6 +37,7 @@ impl SchemaCache {
             tables,
             functions,
             types,
+            versions,
         }
     }
 
diff --git a/crates/pg_schema_cache/src/versions.rs b/crates/pg_schema_cache/src/versions.rs
new file mode 100644
index 00000000..eff70f14
--- /dev/null
+++ b/crates/pg_schema_cache/src/versions.rs
@@ -0,0 +1,43 @@
+use sqlx::PgPool;
+
+use crate::schema_cache::SchemaCacheItem;
+
+#[derive(Debug, Clone, Default)]
+pub struct Version {
+    pub version: Option<String>,
+    pub version_num: Option<i64>,
+    pub active_connections: Option<i64>,
+    pub max_connections: Option<i64>,
+}
+
+impl SchemaCacheItem for Version {
+    type Item = Version;
+
+    async fn load(pool: &PgPool) -> Vec<Version> {
+        sqlx::query_as!(
+            Version,
+            r#"select
+  version(),
+  current_setting('server_version_num') :: int8 AS version_num,
+  (
+    select
+      count(*) :: int8 AS active_connections
+    FROM
+      pg_stat_activity
+  ) AS active_connections,
+  current_setting('max_connections') :: int8 AS max_connections;"#
+        )
+        .fetch_all(pool)
+        .await
+        .unwrap()
+    }
+
+    /*
+    Sample Output:
+    -[ RECORD 1 ]------+--------------------------------------------------------------------------------------------------------------------------
+    version            | PostgreSQL 15.7 (Debian 15.7-1.pgdg120+1) on aarch64-unknown-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit
+    version_num        | 150007
+    active_connections | 8
+    max_connections    | 100
+    */
+}