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sql/run_queries.py

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+"""Execute bundled analytical SQL against SQLite read-only, write real CSVs."""
+import argparse
+import csv
+from pathlib import Path
+import sqlite3
+
+QUERY_NAMES = ('top_categories', 'daily_dynamics', 'anomalies')
+
+
+def run_queries(db, output):
+    output = Path(output)
+    output.mkdir(parents=True, exist_ok=True)
+    uri = Path(db).resolve().as_uri() + '?mode=ro'
+    counts = {}
+    with sqlite3.connect(uri, uri=True) as connection:
+        # One read snapshot keeps reports mutually consistent if a writer runs.
+        connection.execute('BEGIN')
+        for name in QUERY_NAMES:
+            sql = (Path(__file__).parent / f'{name}.sql').read_text(encoding='utf-8')
+            cursor = connection.execute(sql)
+            rows = cursor.fetchall()
+            with (output / f'{name}.csv').open('w', encoding='utf-8', newline='') as stream:
+                writer = csv.writer(stream)
+                writer.writerow([column[0] for column in cursor.description])
+                writer.writerows(rows)
+            counts[name] = len(rows)
+    return counts
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('--db', type=Path, required=True)
+    parser.add_argument('--output', type=Path, required=True)
+    args = parser.parse_args()
+    print(run_queries(args.db, args.output))