Class: TMMUpdater
function Prepare: Boolean;Fetches the target table schema from the server, validates the column
list and mode rules, creates (or validates) the local EDB buffer table,
and opens Table.
Returns True on success.
Errors are reported via OnLog;
LastError is not set by Prepare.
Must be called before Execute when
Table is nil or not active.
When Table is provided and already active,
Prepare validates the supplied table’s field types against
the server schema.
What to set before calling Prepare:
umInsert / umUpsert — set UpdateColumns
and TargetTable.
All non-AUTO_INCREMENT, non-GENERATED primary key columns must be listed
in UpdateColumns.umUpdate — set UpdateColumns
and TargetTable.
Prepare automatically adds primary key columns to the
buffer even when absent from UpdateColumns. At least one
non-PK column must be in UpdateColumns. When the target
table has no PRIMARY KEY, Where must be set
and every :param name in Where must appear in
UpdateColumns.