Hi everyone,
I have a DB migration question. I have a table called "employees" and it has a
UNIQUE constraint on "employee_email". With some new features being requested,
I need to relax the constraint and have a new constraint on "employee_email" +
"employee_number". Since SQLite ALTER table command can't modify an existing
constraint, I have thought about creating a new table with the new constraint
and then copying everything from old table to new table and afterwards dumping
the old table. It does work but my question is what is the fastest and most
memory efficient way to copy data from old table to new table?
Currently we are using:
sql = "INSERT INTO {} SELECT * FROM {}".format(totable, fromtable)
cur.execute(sql)
So, a single line statement can copy from old to new. But will this work fine
even if I have 100s of thousands of records in old table? Or will this load
pretty much entire data into memory and then copy to new?
Looking for other optimal ways to copy data from one table to another if this
is not optimal.
Thanks,
Vikas
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