Refactor database initialization: rename create_tables to init_db, add initialization check, and create _initialized table to prevent re-execution.

Author: Adriano Sanges

init_db.py

@@ -2,60 +2,66 @@
 
 import os
 
-def create_tables(conn):
-    dirname = os.path.dirname(os.path.abspath(__file__))
-    filename = os.path.join(dirname, 'data', 'QI_1106117_1_20241_VALORI.csv')
-    filename_luoghi = os.path.join(dirname, 'data', 'QI_1106117_1_20241_ZONE.csv')
-    create_prezzi_statement = f"CREATE OR REPLACE TABLE prezzi AS select * from '{filename}'"
-    create_luoghi_statement = f"CREATE OR REPLACE TABLE luoghi AS select * from '{filename_luoghi}'"
-    create_joined_data_statement = """
-    CREATE OR REPLACE TABLE joined_data AS
-SELECT
-    p.Area_territoriale,
-    p.Regione,
-    p.Prov,
-    p.Comune_ISTAT,
-    p.Comune_cat,
-    p.Sez,
-    p.Comune_amm,
-    p.Comune_descrizione,
-    p.Fascia,
-    p.Zona,
-    p.LinkZona,
-    p.Cod_Tip,
-    p.Descr_Tipologia,
-    p.Stato,
-    p.Stato_prev,
-    p.Compr_min,
-    p.Compr_max,
-    p.Sup_NL_compr,
-    p.Loc_min,
-    p.Loc_max,
-    p.Sup_NL_loc,
-    p.column21,
-    l.Zona_Descr,
-    l.Cod_tip_prev,
-    l.Descr_tip_prev,
-    l.Stato_prev AS Stato_prev_luoghi,
-    l.Microzona,
-    l.column16
-FROM
-    prezzi AS p
-LEFT JOIN
-    luoghi AS l
-ON
-    p.Area_territoriale = l.Area_territoriale AND
-    p.Regione = l.Regione AND
-    p.Prov = l.Prov AND
-    p.Comune_ISTAT = l.Comune_ISTAT AND
-    p.Comune_cat = l.Comune_cat AND
-    p.Sez = l.Sez AND
-    p.Comune_amm = l.Comune_amm AND
-    p.Comune_descrizione = l.Comune_descrizione AND
-    p.Fascia = l.Fascia AND
-    p.Zona = l.Zona AND
-    p.LinkZona = l.LinkZona;
-    """
-    conn.sql(create_prezzi_statement)
-    conn.sql(create_luoghi_statement)
-    conn.sql(create_joined_data_statement)
+def init_db(conn):
+    try:
+        conn.execute("SELECT 1 FROM _initialized LIMIT 1")
+    except:
+        dirname = os.path.dirname(os.path.abspath(__file__))
+        filename = os.path.join(dirname, 'data', 'QI_1106117_1_20241_VALORI.csv')
+        filename_luoghi = os.path.join(dirname, 'data', 'QI_1106117_1_20241_ZONE.csv')
+        create_prezzi_statement = f"CREATE OR REPLACE TABLE prezzi AS select * from '{filename}'"
+        create_luoghi_statement = f"CREATE OR REPLACE TABLE luoghi AS select * from '{filename_luoghi}'"
+        create_joined_data_statement = """
+        CREATE OR REPLACE TABLE joined_data AS
+        SELECT
+            p.Area_territoriale,
+            p.Regione,
+            p.Prov,
+            p.Comune_ISTAT,
+            p.Comune_cat,
+            p.Sez,
+            p.Comune_amm,
+            p.Comune_descrizione,
+            p.Fascia,
+            p.Zona,
+            p.LinkZona,
+            p.Cod_Tip,
+            p.Descr_Tipologia,
+            p.Stato,
+            p.Stato_prev,
+            p.Compr_min,
+            p.Compr_max,
+            p.Sup_NL_compr,
+            p.Loc_min,
+            p.Loc_max,
+            p.Sup_NL_loc,
+            p.column21,
+            l.Zona_Descr,
+            l.Cod_tip_prev,
+            l.Descr_tip_prev,
+            l.Stato_prev AS Stato_prev_luoghi,
+            l.Microzona,
+            l.column16
+        FROM
+            prezzi AS p
+        LEFT JOIN
+            luoghi AS l
+        ON
+            p.Area_territoriale = l.Area_territoriale AND
+            p.Regione = l.Regione AND
+            p.Prov = l.Prov AND
+            p.Comune_ISTAT = l.Comune_ISTAT AND
+            p.Comune_cat = l.Comune_cat AND
+            p.Sez = l.Sez AND
+            p.Comune_amm = l.Comune_amm AND
+            p.Comune_descrizione = l.Comune_descrizione AND
+            p.Fascia = l.Fascia AND
+            p.Zona = l.Zona AND
+            p.LinkZona = l.LinkZona;
+        """
+        conn.sql(create_prezzi_statement)
+        conn.sql(create_luoghi_statement)
+        conn.sql(create_joined_data_statement)
+        conn.execute("CREATE TABLE _initialized (initialized_at TIMESTAMP);")
+        conn.execute("INSERT INTO _initialized VALUES (CURRENT_TIMESTAMP);")
+

main.py

@@ -2,7 +2,7 @@
 
 import duckdb
 import streamlit as st
-from init_db import create_tables
+from init_db import init_db
 
 @st.cache_data(hash_funcs={duckdb.DuckDBPyConnection: id})
 def get_regioni(conn):
@@ -19,7 +19,7 @@ def main():
     """
     try:
         conn = duckdb.connect(database = "dati-immobiliari.duckdb")
-        create_tables(conn)
+        init_db(conn)
 
         st.set_page_config(layout="wide")
         st.title("Dati immobiliari")