From 9f62d7d4c69baace366db5d85c398223a12e1ac0 Mon Sep 17 00:00:00 2001
From: ilya <ilya@cow.fi>
Date: Mon, 11 Dec 2023 11:31:21 +0000
Subject: [PATCH] Update large tables statistics (#2146)

# Description
After https://github.com/cowprotocol/services/pull/2135 is deployed in
staging, large tables row count metrics are not updated for hours.
Statistics come from `pg_class` table, which is randomly updated by the
DB itself according to internal thresholds. In order to guarantee
statistics update for large tables, a new background task with hourly
rate triggers `ANALYZE {large_table_name}`, which takes around 15s in
staging. That is still significantly faster compared to the initial
`SELECT COUNT(*)` query(150-600s).

# Changes
A new background task running each hour executes `ANALYZE` for each
large table.

## How to test
Logs observation
---
 crates/autopilot/src/database.rs | 37 ++++++++++++++++++++++++++++++--
 crates/autopilot/src/run.rs      |  5 +----
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/crates/autopilot/src/database.rs b/crates/autopilot/src/database.rs
index f641263cb5..54642ea9c8 100644
--- a/crates/autopilot/src/database.rs
+++ b/crates/autopilot/src/database.rs
@@ -12,8 +12,9 @@ mod quotes;
 pub mod recent_settlements;
 
 use {
-    sqlx::{PgConnection, PgPool},
+    sqlx::{Executor, PgConnection, PgPool},
     std::time::Duration,
+    tracing::Instrument,
 };
 
 #[derive(Debug, Clone)]
@@ -50,6 +51,15 @@ impl Postgres {
 
         Ok(())
     }
+
+    pub async fn update_large_tables_stats(&self) -> sqlx::Result<()> {
+        for &table in database::LARGE_TABLES {
+            let mut ex = self.0.acquire().await?;
+            analyze_table(&mut ex, table).await?;
+        }
+
+        Ok(())
+    }
 }
 
 async fn count_rows_in_table(ex: &mut PgConnection, table: &str) -> sqlx::Result<i64> {
@@ -62,6 +72,11 @@ async fn estimate_rows_in_table(ex: &mut PgConnection, table: &str) -> sqlx::Res
     sqlx::query_scalar(&query).fetch_one(ex).await
 }
 
+async fn analyze_table(ex: &mut PgConnection, table: &str) -> sqlx::Result<()> {
+    let query = format!("ANALYZE {table};");
+    ex.execute(sqlx::query(&query)).await.map(|_| ())
+}
+
 async fn count_unused_app_data(ex: &mut PgConnection) -> sqlx::Result<i64> {
     let query = r#"
         SELECT
@@ -99,7 +114,16 @@ impl Metrics {
     }
 }
 
-pub async fn database_metrics(db: Postgres) -> ! {
+pub fn run_database_metrics_work(db: Postgres) {
+    let span = tracing::info_span!("database_metrics");
+    // Spawn the task for updating large table statistics
+    tokio::spawn(update_large_tables_stats(db.clone()).instrument(span.clone()));
+
+    // Spawn the task for database metrics
+    tokio::task::spawn(database_metrics(db).instrument(span));
+}
+
+async fn database_metrics(db: Postgres) -> ! {
     loop {
         if let Err(err) = db.update_database_metrics().await {
             tracing::error!(?err, "failed to update table rows metric");
@@ -108,6 +132,15 @@ pub async fn database_metrics(db: Postgres) -> ! {
     }
 }
 
+async fn update_large_tables_stats(db: Postgres) -> ! {
+    loop {
+        if let Err(err) = db.update_large_tables_stats().await {
+            tracing::error!(?err, "failed to update large tables stats");
+        }
+        tokio::time::sleep(Duration::from_secs(60 * 60)).await;
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/crates/autopilot/src/run.rs b/crates/autopilot/src/run.rs
index 5a452f8218..8c294d24b2 100644
--- a/crates/autopilot/src/run.rs
+++ b/crates/autopilot/src/run.rs
@@ -97,10 +97,7 @@ pub async fn run(args: Arguments) {
     assert!(args.shadow.is_none(), "cannot run in shadow mode");
 
     let db = Postgres::new(args.db_url.as_str()).await.unwrap();
-    tokio::task::spawn(
-        crate::database::database_metrics(db.clone())
-            .instrument(tracing::info_span!("database_metrics")),
-    );
+    crate::database::run_database_metrics_work(db.clone());
 
     let http_factory = HttpClientFactory::new(&args.http_client);
     let web3 = shared::ethrpc::web3(