"""Drop redundant secondary indexes duplicating a named idx_* / unique index.

The DB review found five non-unique secondary indexes that duplicate an existing
index on the same column: the auto-named ix_* from a column index=True alongside
a named idx_* in __table_args__ (communications.assetid, and the hostname on
computers/networkdevices/printers), plus idx_usb_serial duplicating the
serialnumber unique index on usbdevices. Each redundant pair costs insert/update
maintenance with zero read benefit. The models had the redundant index source
removed; this drops the live duplicates so the schema matches the models.

Idempotent (skips a missing table/index); real downgrade recreates them.

Revision ID: 7d25_drop_redundant_indexes
Revises: 7d24_customfield_searchable
Create Date: 2026-07-13

"""
from alembic import op
import sqlalchemy as sa


revision = '7d25_drop_redundant_indexes'
down_revision = '7d24_customfield_searchable'
branch_labels = None
depends_on = None

# (table, index name, columns, unique) - columns/unique used only to recreate on
# downgrade. All non-unique; the surviving idx_* / unique index still covers each.
_REDUNDANT = [
    ('communications', 'ix_communications_assetid', ['assetid'], False),
    ('computers', 'ix_computers_hostname', ['hostname'], False),
    ('networkdevices', 'ix_networkdevices_hostname', ['hostname'], False),
    ('printers', 'ix_printers_hostname', ['hostname'], False),
    ('usbdevices', 'idx_usb_serial', ['serialnumber'], False),
]


def _index_names(insp, table):
    return {i['name'] for i in insp.get_indexes(table)}


def upgrade():
    bind = op.get_bind()
    insp = sa.inspect(bind)
    tables = set(insp.get_table_names())
    for table, name, _cols, _unique in _REDUNDANT:
        if table in tables and name in _index_names(insp, table):
            op.drop_index(name, table_name=table)


def downgrade():
    bind = op.get_bind()
    insp = sa.inspect(bind)
    tables = set(insp.get_table_names())
    for table, name, cols, unique in _REDUNDANT:
        if table in tables and name not in _index_names(insp, table):
            op.create_index(name, table, cols, unique=unique)
