fix timestamp updates, instead of reinserting

schemas/database/010_latest_insertion_timestamp.sql

@@ -1,3 +1,6 @@
 CREATE TABLE latest_insertion_timestamp (
-    insertion_timestamp TIMESTAMPTZ
+    Lock char(1)                NOT NULL DEFAULT 'X',
+    insertion_timestamp         TIMESTAMPTZ,
+    constraint PK_T2            PRIMARY KEY (Lock),
+    constraint CK_T2_Locked     CHECK (Lock='X')
 );

src/database/mod.rs

@@ -369,8 +369,9 @@ impl Database {
     pub async fn get_latest_insertion_timestamp(&self) -> Result<Option<DateTime<Utc>>, Error> {
         let query = sqlx::query(
             r#"
-            SELECT insertion_timestamp FROM latest_insertion_timestamp
-            "#,
+            SELECT insertion_timestamp 
+            FROM latest_insertion_timestamp 
+            WHERE Lock = 'X';"#,
         );
 
         let row = self.pool.fetch_optional(query).await?;
@@ -555,8 +556,10 @@ impl Database {
     ) -> Result<(), Error> {
         let query = sqlx::query(
             r#"
-            INSERT INTO latest_insertion_timestamp (insertion_timestamp)
-            VALUES ($1)
+            INSERT INTO latest_insertion_timestamp (Lock, insertion_timestamp)
+            VALUES ('X', $1)
+            ON CONFLICT (Lock)
+            DO UPDATE SET insertion_timestamp = EXCLUDED.insertion_timestamp;
             "#,
         )
         .bind(insertion_timestamp);

src/task_monitor/tasks/process_identities.rs

@@ -1,11 +1,9 @@
 use std::sync::Arc;
-use std::time::{Duration, SystemTime};
+use std::time::Duration;
 
 use anyhow::{Context, Result as AnyhowResult};
 use chrono::{DateTime, Utc};
 use ethers::types::U256;
-use futures_util::TryFutureExt;
-use oz_api::data;
 use ruint::Uint;
 use semaphore::merkle_tree::Proof;
 use semaphore::poseidon_tree::Branch;