From: Michael Tremer <michael.tremer@ipfire.org>
Date: Thu, 9 Dec 2021 15:57:20 +0000 (+0000)
Subject: db: Store a timestamp when the database was modified last
X-Git-Tag: 0.9.28~819
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7b4df7659e6f98f6bc662573ea539f4df22d290d;p=pakfire.git

db: Store a timestamp when the database was modified last

This is useful to detect whether things have changed since the database
was opened and whether things have to be re-read from it.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/libpakfire/db.c b/src/libpakfire/db.c
index 2edd73241..9deaca54e 100644
--- a/src/libpakfire/db.c
+++ b/src/libpakfire/db.c
@@ -50,6 +50,7 @@ struct pakfire_db {
 
 	sqlite3* handle;
 	int schema;
+	time_t last_modified_at;
 };
 
 static void logging_callback(void* data, int r, const char* msg) {
@@ -59,62 +60,6 @@ static void logging_callback(void* data, int r, const char* msg) {
 		sqlite3_errstr(r), msg);
 }
 
-static int pakfire_db_execute(struct pakfire_db* db, const char* stmt) {
-	int r;
-
-	DEBUG(db->pakfire, "Executing database query: %s\n", stmt);
-
-	do {
-		r = sqlite3_exec(db->handle, stmt, NULL, NULL, NULL);
-	} while (r == SQLITE_BUSY);
-
-	// Log any errors
-	if (r) {
-		ERROR(db->pakfire, "Database query failed: %s\n", sqlite3_errmsg(db->handle));
-	}
-
-	return r;
-}
-
-static int pakfire_db_begin_transaction(struct pakfire_db* db) {
-	return pakfire_db_execute(db, "BEGIN TRANSACTION");
-}
-
-static int pakfire_db_commit(struct pakfire_db* db) {
-	return pakfire_db_execute(db, "COMMIT");
-}
-
-static int pakfire_db_rollback(struct pakfire_db* db) {
-	return pakfire_db_execute(db, "ROLLBACK");
-}
-
-/*
-	This function performs any fast optimization and tries to truncate the WAL log file
-	to keep the database as compact as possible on disk.
-*/
-static void pakfire_db_optimize(struct pakfire_db* db) {
-	pakfire_db_execute(db, "PRAGMA optimize");
-	pakfire_db_execute(db, "PRAGMA wal_checkpoint = TRUNCATE");
-}
-
-static void pakfire_db_free(struct pakfire_db* db) {
-	if (db->handle) {
-		// Optimize the database before it is being closed
-		pakfire_db_optimize(db);
-
-		// Close database handle
-		int r = sqlite3_close(db->handle);
-		if (r != SQLITE_OK) {
-			ERROR(db->pakfire, "Could not close database handle: %s\n",
-				sqlite3_errmsg(db->handle));
-		}
-	}
-
-	pakfire_unref(db->pakfire);
-
-	free(db);
-}
-
 static sqlite3_value* pakfire_db_get(struct pakfire_db* db, const char* key) {
 	sqlite3_stmt* stmt = NULL;
 	sqlite3_value* val = NULL;
@@ -167,6 +112,8 @@ static int pakfire_db_set_int(struct pakfire_db* db, const char* key, int val) {
 	sqlite3_stmt* stmt = NULL;
 	int r;
 
+	DEBUG(db->pakfire, "Setting %s to '%d'\n", key, val);
+
 	const char* sql = "INSERT INTO settings(key, val) VALUES(?, ?) \
 		ON CONFLICT (key) DO UPDATE SET val = excluded.val";
 
@@ -207,6 +154,103 @@ ERROR:
 	return r;
 }
 
+static time_t pakfire_read_modification_time(struct pakfire_db* db) {
+	time_t t = 0;
+
+	// Fetch the value from the database
+	sqlite3_value* value = pakfire_db_get(db, "last_modified_at");
+	if (value) {
+		t = sqlite3_value_int64(value);
+		sqlite3_value_free(value);
+	} else {
+		DEBUG(db->pakfire, "Could not find last modification timestamp\n");
+	}
+
+	return t;
+}
+
+static int pakfire_update_modification_time(struct pakfire_db* db) {
+	// Get the current time in UTC
+	time_t t = time(NULL);
+
+	// Store it in the database
+	int r = pakfire_db_set_int(db, "last_modified_at", t);
+	if (r)
+		return r;
+
+	// Update the last modification timestamp
+	db->last_modified_at = t;
+
+	return r;
+}
+
+static int pakfire_db_execute(struct pakfire_db* db, const char* stmt) {
+	int r;
+
+	DEBUG(db->pakfire, "Executing database query: %s\n", stmt);
+
+	do {
+		r = sqlite3_exec(db->handle, stmt, NULL, NULL, NULL);
+	} while (r == SQLITE_BUSY);
+
+	// Log any errors
+	if (r) {
+		ERROR(db->pakfire, "Database query failed: %s\n", sqlite3_errmsg(db->handle));
+	}
+
+	return r;
+}
+
+static int pakfire_db_begin_transaction(struct pakfire_db* db) {
+	return pakfire_db_execute(db, "BEGIN TRANSACTION");
+}
+
+static int pakfire_db_commit(struct pakfire_db* db) {
+	/*
+		If the database was opened in read-write mode, we will store the
+		timestamp of the latest modification to compare whether the database
+		has been changed mid-transaction.
+	*/
+	if (db->mode == PAKFIRE_DB_READWRITE) {
+		int r = pakfire_update_modification_time(db);
+		if (r)
+			return r;
+	}
+
+	return pakfire_db_execute(db, "COMMIT");
+}
+
+static int pakfire_db_rollback(struct pakfire_db* db) {
+	return pakfire_db_execute(db, "ROLLBACK");
+}
+
+/*
+	This function performs any fast optimization and tries to truncate the WAL log file
+	to keep the database as compact as possible on disk.
+*/
+static void pakfire_db_optimize(struct pakfire_db* db) {
+	pakfire_db_execute(db, "PRAGMA optimize");
+	pakfire_db_execute(db, "PRAGMA wal_checkpoint = TRUNCATE");
+}
+
+static void pakfire_db_free(struct pakfire_db* db) {
+	if (db->handle) {
+		// Optimize the database before it is being closed
+		pakfire_db_optimize(db);
+
+		// Close database handle
+		int r = sqlite3_close(db->handle);
+		if (r != SQLITE_OK) {
+			ERROR(db->pakfire, "Could not close database handle: %s\n",
+				sqlite3_errmsg(db->handle));
+		}
+	}
+
+	pakfire_unref(db->pakfire);
+
+	free(db);
+}
+
 static int pakfire_db_get_schema(struct pakfire_db* db) {
 	sqlite3_value* value = pakfire_db_get(db, "schema");
 	if (!value)
@@ -419,6 +463,11 @@ static int pakfire_db_setup(struct pakfire_db* db) {
 		return 1;
 	}
 
+	// Read modification timestamp
+	db->last_modified_at = pakfire_read_modification_time(db);
+
+	DEBUG(db->pakfire, "The database was last modified at %ld\n", db->last_modified_at);
+
 	// Done when not in read-write mode
 	if (db->mode != PAKFIRE_DB_READWRITE)
 		return 0;