[odb-users] Creating schema and adding tables without dropping data
ellav at checkpoint.com
Wed Apr 20 03:52:17 EDT 2016
I'm using 2.3.0 version & sqlite
I wanted to implement the following scenario:
1. Check if sqlite db file exists:
a. Does not exist :
i. Create new file with all tables that have the "db object" pragma.
i. Add the new tables without erasing data from old tables
I started with the first one, but seems that the file is not being created.
This is the field : odb::database *m_db;
Create function: void Init_OneDB(const std::string &_db_name, long _mode = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE);
Implementation: m_db = new odb::sqlite::database("TEST_ONE_DB",_mode);
Although the file does not exist, an empty file is not being created.
a. I thought of using schema_catalog::exists(*m_db) but it returns true.
b. I thought of persisting dummy entity but I get crash : terminate called after throwing an instance of 'odb::sqlite::database_exception'
what(): 1 (0): no such table: person.
c. I looked at the example of schema/embedded and creating it by using query on person & creating schema if exception is being caught.
That worked but how can it be implemented when a file exists, but new tables should be inserted.
For example : my sqlite file contains person table. If the sqlite file does not exit - > the query fails -> I reach the catch exception and use the schema_catalog::create_schema.
Now I added a new table : person2. How can I "merge" it? The code will query person->see that it exits -> and won't use create_schema -> person2 will not be added.
On the other hand, if I always use create_schema - I will delete all my data.
m_db = new odb::sqlite::database("TEST_ONE_DB",_mode);
typedef odb::query<CPerson> query;
typedef odb::result<CPerson> result;
odb::transaction t (m_db->begin ());
catch(const odb::exception& e)
std::cout << "***** CREATING SCHEMA ****** " << std::endl;
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