Method _save_table

django/db/models/base.py:1061–1196

Do the heavy-lifting involved in saving. Update or insert the data for a single table.

(
        self,
        raw=False,
        cls=None,
        force_insert=False,
        force_update=False,
        using=None,
        update_fields=None,
    )

        return inserted

    def _save_table(
        self,
        raw=False,
        cls=None,
        force_insert=False,
        force_update=False,
        using=None,
        update_fields=None,
    ):
        """
        Do the heavy-lifting involved in saving. Update or insert the data
        for a single table.
        """
        meta = cls._meta
        pk_fields = meta.pk_fields
        non_pks_non_generated = [
            f
            for f in meta.local_concrete_fields
            if f not in pk_fields and not f.generated
        ]

        if update_fields:
            non_pks_non_generated = [
                f
                for f in non_pks_non_generated
                if f.name in update_fields or f.attname in update_fields
            ]

        if not self._is_pk_set(meta):
            pk_val = meta.pk.get_pk_value_on_save(self)
            setattr(self, meta.pk.attname, pk_val)
        pk_set = self._is_pk_set(meta)
        if not pk_set and (force_update or update_fields):
            raise ValueError("Cannot force an update in save() with no primary key.")
        updated = False
        # Skip an UPDATE when adding an instance and primary key has a default.
        if (
            not raw
            and not force_insert
            and not force_update
            and self._state.adding
            and all(f.has_default() or f.has_db_default() for f in meta.pk_fields)
        ):
            force_insert = True
        # If possible, try an UPDATE. If that doesn't update anything, do an
        # INSERT.
        if pk_set and not force_insert:
            base_qs = cls._base_manager.using(using)
            values = [
                (
                    f,
                    None,
                    (getattr(self, f.attname) if raw else f.pre_save(self, False)),
                )
                for f in non_pks_non_generated
            ]
            forced_update = update_fields or force_update
            pk_val = self._get_pk_val(meta)