db: support mode where we don't want to create the db.

diff --git a/db/common.h b/db/common.h
index 05436ef6..1ffd2634 100644
--- a/db/common.h
+++ b/db/common.h
@@ -183,7 +183,7 @@ struct db_config {
 	u64 (*last_insert_id_fn)(struct db_stmt *stmt);
 	size_t (*count_changes_fn)(struct db_stmt *stmt);
 
-	bool (*setup_fn)(struct db *db);
+	bool (*setup_fn)(struct db *db, bool create);
 	void (*teardown_fn)(struct db *db);
 
 	bool (*vacuum_fn)(struct db *db);
diff --git a/db/db_postgres.c b/db/db_postgres.c
index 68cfd956..ae9785c6 100644
--- a/db/db_postgres.c
+++ b/db/db_postgres.c
@@ -14,7 +14,7 @@
 #define INT4OID			23
 #define TEXTOID			25
 
-static bool db_postgres_setup(struct db *db)
+static bool db_postgres_setup(struct db *db, bool create)
 {
 	size_t prefix_len = strlen("postgres://");
 
diff --git a/db/db_sqlite3.c b/db/db_sqlite3.c
index 171c0e06..c34acc51 100644
--- a/db/db_sqlite3.c
+++ b/db/db_sqlite3.c
@@ -98,20 +98,23 @@ static const char *db_sqlite3_fmt_error(struct db_stmt *stmt)
 		       sqlite3_errmsg(conn2sql(stmt->db->conn)));
 }
 
-static bool db_sqlite3_setup(struct db *db)
+static bool db_sqlite3_setup(struct db *db, bool create)
 {
 	char *filename;
 	char *sep;
 	char *backup_filename = NULL;
 	sqlite3_stmt *stmt;
 	sqlite3 *sql;
-	int err, flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE;
-
+	int err, flags;
 	struct db_sqlite3 *wrapper;
 
 	if (!strstarts(db->filename, "sqlite3://") || strlen(db->filename) < 10)
 		db_fatal(db, "Could not parse the wallet DSN: %s", db->filename);
 
+	flags = SQLITE_OPEN_READWRITE;
+	if (create)
+		flags |= SQLITE_OPEN_CREATE;
+
 	/* Strip the scheme from the dsn. */
 	filename = db->filename + strlen("sqlite3://");
 	/* Look for a replica specification.  */
@@ -126,8 +129,11 @@ static bool db_sqlite3_setup(struct db *db)
 	db->conn = wrapper;
 
 	err = sqlite3_open_v2(filename, &sql, flags, NULL);
-
 	if (err != SQLITE_OK) {
+		/* Note: even on error, the sql connection is allocated! */
+		sqlite3_close(sql);
+		if (!create)
+			return false;
 		db_fatal(db, "failed to open database %s: %s", filename,
 			 sqlite3_errstr(err));
 	}
diff --git a/db/utils.c b/db/utils.c
index 70389907..155efbd4 100644
--- a/db/utils.c
+++ b/db/utils.c
@@ -333,6 +333,7 @@ void db_warn(const struct db *db, const char *fmt, ...)
 
 struct db *db_open_(const tal_t *ctx, const char *filename,
 		    bool developer,
+		    bool create,
 		    void (*errorfn)(void *arg, bool fatal, const char *fmt, va_list ap),
 		    void *arg)
 {
@@ -356,7 +357,6 @@ struct db *db_open_(const tal_t *ctx, const char *filename,
 	if (!db->queries)
 		db_fatal(db, "Unable to find DB queries for %s", db->config->name);
 
-	tal_add_destructor(db, destroy_db);
 	db->in_transaction = NULL;
 	db->changes = NULL;
 
@@ -365,10 +365,15 @@ struct db *db_open_(const tal_t *ctx, const char *filename,
 
 	trace_span_start("db_setup", db);
 	db_prepare_for_changes(db);
-	if (db->config->setup_fn && !db->config->setup_fn(db))
-		db_fatal(db, "Error calling DB setup: %s", db->error);
+	if (!db->config->setup_fn(db, create)) {
+		if (create)
+			db_fatal(db, "Error calling DB setup: %s", db->error);
+		trace_span_end(db);
+		return tal_free(db);
+	}
 	db_report_changes(db, NULL, 0);
 	trace_span_end(db);
 
+	tal_add_destructor(db, destroy_db);
 	return db;
 }
diff --git a/db/utils.h b/db/utils.h
index 0cb699ee..859741f8 100644
--- a/db/utils.h
+++ b/db/utils.h
@@ -83,15 +83,16 @@ struct db_stmt *db_prepare_v2_(const char *location, struct db *db,
 			       const char *query_id);
 
 /**
- * db_open - Open or create a database
+ * db_open - Open or create (if create set) a database
  */
-#define db_open(ctx, filename, developer, errfn, arg)		\
-	db_open_((ctx), (filename), (developer),			\
+#define db_open(ctx, filename, developer, create, errfn, arg)		\
+	db_open_((ctx), (filename), (developer), (create),		\
 		 typesafe_cb_postargs(void, void *, (errfn), (arg),	\
 				      bool, const char *, va_list),		\
 		 (arg))
 
 struct db *db_open_(const tal_t *ctx, const char *filename, bool developer,
+		    bool create,
 		    void (*errorfn)(void *arg, bool fatal, const char *fmt, va_list ap),
 		    void *arg);
 
diff --git a/wallet/db.c b/wallet/db.c
index c97d2960..faae6161 100644
--- a/wallet/db.c
+++ b/wallet/db.c
@@ -1171,7 +1171,7 @@ static void db_error(struct lightningd *ld, bool fatal, const char *fmt, va_list
 struct db *db_setup(const tal_t *ctx, struct lightningd *ld,
 		    const struct ext_key *bip32_base)
 {
-	struct db *db = db_open(ctx, ld->wallet_dsn, ld->developer,
+	struct db *db = db_open(ctx, ld->wallet_dsn, ld->developer, true,
 				db_error, ld);
 	bool migrated;
 
diff --git a/wallet/test/run-db.c b/wallet/test/run-db.c
index d9a99d8f..a010a1b0 100644
--- a/wallet/test/run-db.c
+++ b/wallet/test/run-db.c
@@ -427,7 +427,7 @@ static struct db *create_test_db(void)
 
 	dsn = tal_fmt(NULL, "sqlite3://%s", filename);
 	tal_free(filename);
-	db = db_open(NULL, dsn, true, db_error, (struct lightningd *)NULL);
+	db = db_open(NULL, dsn, true, true, db_error, (struct lightningd *)NULL);
 	db->data_version = 0;
 	db->report_changes_fn = NULL;
 
diff --git a/wallet/test/run-wallet.c b/wallet/test/run-wallet.c
index 2caa7d9e..31c8f91b 100644
--- a/wallet/test/run-wallet.c
+++ b/wallet/test/run-wallet.c
@@ -1348,7 +1348,7 @@ static struct wallet *create_test_wallet(struct lightningd *ld, const tal_t *ctx
 	close(fd);
 
 	dsn = tal_fmt(NULL, "sqlite3://%s", filename);
-	w->db = db_open(w, dsn, true, test_error, ld);
+	w->db = db_open(w, dsn, true, true, test_error, ld);
 	w->db->report_changes_fn = NULL;
 	tal_free(dsn);
 	tal_add_destructor2(w, cleanup_test_wallet, filename);