feat: schedule & query jobs efficiently in batches

src/scraper/scheduler.rs

@@ -6,7 +6,7 @@ use sqlx::PgPool;
 use std::sync::Arc;
 use std::time::Duration;
 use tokio::time;
-use tracing::{error, info, debug, trace};
+use tracing::{debug, error, info, trace};
 
 /// Periodically analyzes data and enqueues prioritized scrape jobs.
 pub struct Scheduler {
@@ -40,42 +40,76 @@ impl Scheduler {
     async fn schedule_jobs(&self) -> Result<()> {
         // For now, we will implement a simple baseline scheduling strategy:
         // 1. Get a list of all subjects from the Banner API.
-        // 2. For each subject, check if an active (not locked, not completed) job already exists.
-        // 3. If no job exists, create a new, low-priority job to be executed in the near future.
+        // 2. Query existing jobs for all subjects in a single query.
+        // 3. Create new jobs only for subjects that don't have existing jobs.
         let term = Term::get_current().inner().to_string();
 
         debug!(term = term, "Enqueuing subject jobs");
 
         let subjects = self.banner_api.get_subjects("", &term, 1, 500).await?;
-        debug!(subject_count = subjects.len(), "Retrieved subjects from API");
+        debug!(
+            subject_count = subjects.len(),
+            "Retrieved subjects from API"
+        );
 
-        for subject in subjects {
-            let payload = json!({ "subject": subject.code });
+        // Create payloads for all subjects
+        let subject_payloads: Vec<_> = subjects
+            .iter()
+            .map(|subject| json!({ "subject": subject.code }))
+            .collect();
 
-            let existing_job: Option<(i32,)> = sqlx::query_as(
-                "SELECT id FROM scrape_jobs WHERE target_type = $1 AND target_payload = $2 AND locked_at IS NULL"
-            )
-            .bind(TargetType::Subject)
-            .bind(&payload)
-            .fetch_optional(&self.db_pool)
-            .await?;
+        // Query existing jobs for all subjects in a single query
+        let existing_jobs: Vec<(serde_json::Value,)> = sqlx::query_as(
+            "SELECT target_payload FROM scrape_jobs 
+             WHERE target_type = $1 AND target_payload = ANY($2) AND locked_at IS NULL",
+        )
+        .bind(TargetType::Subject)
+        .bind(&subject_payloads)
+        .fetch_all(&self.db_pool)
+        .await?;
 
-            if existing_job.is_some() {
-                trace!(subject = subject.code, "Job already exists, skipping");
-                continue;
+        // Convert to a HashSet for efficient lookup
+        let existing_payloads: std::collections::HashSet<String> = existing_jobs
+            .into_iter()
+            .map(|(payload,)| payload.to_string())
+            .collect();
+
+        // Filter out subjects that already have jobs and prepare new jobs
+        let new_jobs: Vec<_> = subjects
+            .into_iter()
+            .filter_map(|subject| {
+                let payload = json!({ "subject": subject.code });
+                let payload_str = payload.to_string();
+
+                if existing_payloads.contains(&payload_str) {
+                    trace!(subject = subject.code, "Job already exists, skipping");
+                    None
+                } else {
+                    Some((payload, subject.code))
+                }
+            })
+            .collect();
+
+        // Insert all new jobs in a single batch
+        if !new_jobs.is_empty() {
+            let now = chrono::Utc::now();
+            let mut tx = self.db_pool.begin().await?;
+
+            for (payload, subject_code) in new_jobs {
+                sqlx::query(
+                    "INSERT INTO scrape_jobs (target_type, target_payload, priority, execute_at) VALUES ($1, $2, $3, $4)"
+                )
+                .bind(TargetType::Subject)
+                .bind(&payload)
+                .bind(ScrapePriority::Low)
+                .bind(now)
+                .execute(&mut *tx)
+                .await?;
+
+                debug!(subject = subject_code, "New job enqueued for subject");
             }
 
-            sqlx::query(
-                "INSERT INTO scrape_jobs (target_type, target_payload, priority, execute_at) VALUES ($1, $2, $3, $4)"
-            )
-            .bind(TargetType::Subject)
-            .bind(&payload)
-            .bind(ScrapePriority::Low)
-            .bind(chrono::Utc::now())
-            .execute(&self.db_pool)
-            .await?;
-
-            debug!(subject = subject.code, "New job enqueued for subject");
+            tx.commit().await?;
         }
 
         debug!("Job scheduling complete");