add database schema versioning to the HLR database

Make use of pragma user_version to store our database schema version.
The present schema is now identitifed as 'version 0', which is also
the default value for databases on which we never ran the statement
'pragma user_version' before.

Only bootstrap the database if it hasn't been bootstrapped yet.
Previously, bootstrap SQL statements ran every time osmo-hlr
opened the database, and any errors were being ignored in SQL.
Instead, we now first run a query which checks whether tables
already exist, and only create them if necessary.
This change will allow future schema updates to work properly.

Prepare for future schema upgrades by adding a new command-line
option which enables upgrades. This option defaults to 'false'
in order to avoid accidental upgrades.

Change-Id: I8aeaa9a404b622657cbc7138106f38aa6ad8d01b
Related: OS#2838

1 files changed, 99 insertions, 13 deletions

diff --git a/src/db.c b/src/db.c
index bcf83c6..df52f9b 100644
--- a/src/db.c
+++ b/src/db.c
@@ -27,6 +27,8 @@
 #include "db.h"
 #include "db_bootstrap.h"
 
+#define CURRENT_SCHEMA_VERSION	0
+
 #define SEL_COLUMNS \
 	"id," \
 	"imsi," \
@@ -197,36 +199,90 @@ static int db_bootstrap(struct db_context *dbc)
 	for (i = 0; i < ARRAY_SIZE(stmt_bootstrap_sql); i++) {
 		int rc;
 		sqlite3_stmt *stmt;
-
-		rc = sqlite3_prepare_v2(dbc->db, stmt_bootstrap_sql[i], -1,
-					&stmt, NULL);
+		rc = sqlite3_prepare_v2(dbc->db, stmt_bootstrap_sql[i], -1, &stmt, NULL);
 		if (rc != SQLITE_OK) {
-			LOGP(DDB, LOGL_ERROR, "Unable to prepare SQL statement '%s'\n",
-			     stmt_bootstrap_sql[i]);
+			LOGP(DDB, LOGL_ERROR, "Unable to prepare SQL statement '%s'\n", stmt_bootstrap_sql[i]);
 			return rc;
 		}
 
-		/* execute the statement */
 		rc = sqlite3_step(stmt);
 		db_remove_reset(stmt);
 		sqlite3_finalize(stmt);
 		if (rc != SQLITE_DONE) {
 			LOGP(DDB, LOGL_ERROR, "Cannot bootstrap database: SQL error: (%d) %s,"
 			     " during stmt '%s'",
-			     rc, sqlite3_errmsg(dbc->db),
-			     stmt_bootstrap_sql[i]);
+			     rc, sqlite3_errmsg(dbc->db), stmt_bootstrap_sql[i]);
 			return rc;
 		}
 	}
 	return SQLITE_OK;
 }
 
-struct db_context *db_open(void *ctx, const char *fname, bool enable_sqlite_logging)
+/* https://www.sqlite.org/fileformat2.html#storage_of_the_sql_database_schema */
+static bool db_table_exists(struct db_context *dbc, const char *table_name)
+{
+	const char *table_exists_sql = "SELECT name FROM sqlite_master WHERE type='table' AND name=?";
+	sqlite3_stmt *stmt;
+	int rc;
+
+	rc = sqlite3_prepare_v2(dbc->db, table_exists_sql, -1, &stmt, NULL);
+	if (rc != SQLITE_OK) {
+		LOGP(DDB, LOGL_ERROR, "Unable to prepare SQL statement '%s'\n", table_exists_sql);
+		return false;
+	}
+
+	if (!db_bind_text(stmt, NULL, table_name))
+		return false;
+
+	rc = sqlite3_step(stmt);
+	db_remove_reset(stmt);
+	sqlite3_finalize(stmt);
+	return (rc == SQLITE_ROW);
+}
+
+/* Indicate whether the database is initialized with tables for schema version 0.
+ * We only check for the 'subscriber' table here because Neels said so. */
+static bool db_is_bootstrapped_v0(struct db_context *dbc)
+{
+	if (!db_table_exists(dbc, "subscriber")) {
+		LOGP(DDB, LOGL_DEBUG, "Table 'subscriber' not found in database '%s'\n", dbc->fname);
+		return false;
+	}
+
+	return true;
+}
+
+static int db_get_user_version(struct db_context *dbc)
+{
+	const char *user_version_sql = "PRAGMA user_version";
+	sqlite3_stmt *stmt;
+	int version, rc;
+
+	rc = sqlite3_prepare_v2(dbc->db, user_version_sql, -1, &stmt, NULL);
+	if (rc != SQLITE_OK) {
+		LOGP(DDB, LOGL_ERROR, "Unable to prepare SQL statement '%s'\n", user_version_sql);
+		return -1;
+	}
+	rc = sqlite3_step(stmt);
+	if (rc == SQLITE_ROW) {
+		version = sqlite3_column_int(stmt, 0);
+	} else {
+		LOGP(DDB, LOGL_ERROR, "SQL statement '%s' failed: %d\n", user_version_sql, rc);
+		version = -1;
+	}
+
+	db_remove_reset(stmt);
+	sqlite3_finalize(stmt);
+	return version;
+}
+
+struct db_context *db_open(void *ctx, const char *fname, bool enable_sqlite_logging, bool allow_upgrade)
 {
 	struct db_context *dbc = talloc_zero(ctx, struct db_context);
 	unsigned int i;
 	int rc;
 	bool has_sqlite_config_sqllog = false;
+	int version;
 
 	LOGP(DDB, LOGL_NOTICE, "using database: %s\n", fname);
 	LOGP(DDB, LOGL_INFO, "Compiled against SQLite3 lib version %s\n", SQLITE_VERSION);
@@ -275,10 +331,40 @@ struct db_context *db_open(void *ctx, const char *fname, bool enable_sqlite_logg
 		LOGP(DDB, LOGL_ERROR, "Unable to set Write-Ahead Logging: %s\n",
 			err_msg);
 
-	rc = db_bootstrap(dbc);
-	if (rc != SQLITE_OK) {
-		LOGP(DDB, LOGL_ERROR, "Failed to bootstrap DB: (rc=%d) %s\n",
-			rc, sqlite3_errmsg(dbc->db));
+	version = db_get_user_version(dbc);
+	if (version < 0) {
+		LOGP(DDB, LOGL_ERROR, "Unable to read user version number from database '%s'\n", dbc->fname);
+		goto out_free;
+	}
+
+	/* An empty database will always report version zero. */
+	if (version == 0 && !db_is_bootstrapped_v0(dbc)) {
+		LOGP(DDB, LOGL_NOTICE, "Missing database tables detected; Bootstrapping database '%s'\n", dbc->fname);
+		rc = db_bootstrap(dbc);
+		if (rc != SQLITE_OK) {
+			LOGP(DDB, LOGL_ERROR, "Failed to bootstrap DB: (rc=%d) %s\n",
+			     rc, sqlite3_errmsg(dbc->db));
+			goto out_free;
+		}
+	}
+
+	LOGP(DDB, LOGL_NOTICE, "Database '%s' has HLR DB schema version %d\n", dbc->fname, version);
+
+	if (version < CURRENT_SCHEMA_VERSION && allow_upgrade) {
+		/* Future version upgrades will happen here. */
+	}
+
+	if (version != CURRENT_SCHEMA_VERSION) {
+		if (version < CURRENT_SCHEMA_VERSION) {
+			LOGP(DDB, LOGL_NOTICE, "HLR DB schema version %d is outdated\n", version);
+			if (!allow_upgrade) {
+				LOGP(DDB, LOGL_ERROR, "Not upgrading HLR database to schema version %d; "
+				     "use the --db-upgrade option to allow HLR database upgrades\n",
+				     CURRENT_SCHEMA_VERSION);
+			}
+		} else
+			LOGP(DDB, LOGL_ERROR, "HLR DB schema version %d is unknown\n", version);
+
 		goto out_free;
 	}