sqlite - Database Is Locked

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This error code occurs when you try to do to incompatible things with a database at the same time from the same database connection. For example, if you are in the middle of a SELECT statement and you try to DROP one of the tables being read by the SELECT, you will get an SQLITE_LOCKED error. Here is an example (using Tcl):

   db eval {SELECT rowid FROM ex1} {
     if {$rowid==10} {
       db eval {DROP TABLE ex1}  ;# will give SQLITE_LOCKED error
     }
   }

Note that an SQLITE_LOCKED error is distinct from SQLITE_BUSY (5). SQLITE_BUSY means that another database connection (probably in another process) is using the database in a way that prevents you from using it. SQLITE_LOCKED means the source of contention is internal and comes from the same database connection that received the SQLITE_LOCKED error.

Here are other reasons for getting an SQLITE_LOCKED error:

1. Trying to CREATE or DROP a table or index while a SELECT statement is still pending.
   • Sometimes people think they have finished with a SELECT statement because sqlite3_step() has returned SQLITE_DONE. But the SELECT is not really complete until sqlite3_reset() or sqlite3_finalize() have been called.

2. Trying to write to a table while a SELECT is active on that same table.
   • As of check-in [3355] (2006-08-16 after version 3.3.7) this is now allowed.