sqlite3_vtab
—
Virtual Table Instance Object
Every virtual table module implementation uses a subclass of this object to
describe a particular instance of the virtual table. Each subclass will be
tailored to the specific needs of the module implementation. The purpose of
this superclass is to define certain fields that are common to all module
implementations.
Virtual tables methods can set an error message by assigning a
string obtained from sqlite3_mprintf() to zErrMsg. The method should take
care that any prior string is freed by a call to sqlite3_free() prior to
assigning a new string to zErrMsg. After the error message is delivered up
to the client application, the string will be automatically freed by
sqlite3_free() and the zErrMsg field will be zeroed.