Add assertion for mismatch of result set column count in MySQL and SQLite

This is useful for detecting native views that happened to have stray data
members. Also update comment in PostgreSQL.

1 files changed, 7 insertions, 0 deletions

diff --git a/odb/sqlite/statement.cxx b/odb/sqlite/statement.cxx
index 6417b3a..9071f68 100644
--- a/odb/sqlite/statement.cxx
+++ b/odb/sqlite/statement.cxx
@@ -114,6 +114,13 @@ namespace odb
     bool statement::
     bind_result (const bind* p, size_t n, bool truncated)
     {
+      // Make sure that the number of columns in the result returned by
+      // the database matches the number that we expect. A common cause
+      // of this assertion is a native view with a number of data members
+      // not matching the number of columns in the SELECT-list.
+      //
+      assert (static_cast<size_t> (sqlite3_data_count (stmt_)) == n);
+
       bool r (true);
 
       for (size_t i (0); i < n; ++i)