prep statement, use join to exclude existing

app/lib/blob_entry_sample_exporter.rb

@@ -65,16 +65,26 @@ class BlobEntrySampleExporter
           bind_nums = batch.size.times.map { |idx| "$#{idx + 1}" }
 
           query = <<-SQL
-            INSERT INTO blob_entries_p
-            (
-                SELECT sha256, base_sha256, content_type, size, contents, created_at
-                FROM blob_entries
-                WHERE sha256 IN (#{bind_nums.join(", ")})
-                AND sha256 NOT IN (select sha256 from blob_entries_p)
+            INSERT INTO blob_entries_p (
+              SELECT
+                be.sha256,
+                be.base_sha256,
+                be.content_type,
+                be.size,
+                be.contents,
+                be.created_at
+              FROM
+                blob_entries be
+              LEFT JOIN
+                blob_entries_p bep ON be.sha256 = bep.sha256
+              WHERE
+                bep.sha256 IS NULL
+              AND
+                be.sha256 IN (#{bind_nums.join(", ")})
             ) RETURNING sha256
           SQL
 
-          result = connection.exec_query query, "SQL", binds
+          result = connection.exec_query query, "SQL", binds, prepare: true
           num_inserted = result.rows.length
           total_inserted += num_inserted
           num_inserted