add index creation to migration scripts (#4296)

and remove the one-off `run_non_transactional_migrations`.

For existing prod DBs this is a no-op; for fresh DBs the table is empty,
so a non-concurrent build is fine.

Will add a comment in the next release note about this so anyone using
this in prod can also create this index before performing the upgrade.

Author: jgao54

nexus/Cargo.lock

@@ -0,0 +1 @@
+CREATE INDEX IF NOT EXISTS idx_cdc_batches_flow_name_batch_id_open ON peerdb_stats.cdc_batches (flow_name, batch_id) WHERE end_time IS NULL;

nexus/catalog/migrations/V53__cdc_batches_open_index.sql

@@ -151,20 +151,6 @@ async fn run_migrations(client: &mut Client) -> anyhow::Result<()> {
             migration.version()
         );
     }
-    run_non_transactional_migrations(client).await?;
-    Ok(())
-}
-
-async fn run_non_transactional_migrations(client: &Client) -> anyhow::Result<()> {
-    const STATEMENTS: &[&str] = &[
-        "CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_cdc_batches_flow_name_batch_id_open ON peerdb_stats.cdc_batches (flow_name, batch_id) WHERE end_time IS NULL",
-    ];
-    for stmt in STATEMENTS {
-        client
-            .batch_execute(stmt)
-            .await
-            .with_context(|| format!("Failed to apply non-transactional migration: {stmt}"))?;
-    }
     Ok(())
 }