"""add ivfflat index for knowledge chunk embedding

Revision ID: add_kb_chunk_ivfflat_index
Revises: add_pg_trgm_text_indexes
Create Date: 2026-03-11
"""

from __future__ import annotations

from alembic import op


revision = "add_kb_chunk_ivfflat_index"
down_revision = "add_pg_trgm_text_indexes"
branch_labels = None
depends_on = None


def _is_postgresql() -> bool:
    bind = op.get_bind()
    return str(getattr(getattr(bind, "dialect", None), "name", "")).lower().startswith("postgres")


def upgrade() -> None:
    if not _is_postgresql():
        return

    op.execute(
        """
        CREATE INDEX IF NOT EXISTS ix_knowledge_chunks_embedding_ivfflat
        ON knowledge_base_chunks
        USING ivfflat (embedding vector_cosine_ops)
        WITH (lists = 100)
        """
    )


def downgrade() -> None:
    if not _is_postgresql():
        return

    op.execute("DROP INDEX IF EXISTS ix_knowledge_chunks_embedding_ivfflat")