"""Phase 1 — confirm pgvector activation on memory_associative.

Migration 004 created the embedding column as vector(1536) and added the
IVFFlat index.  This migration is the Phase-1 checkpoint:
  1. Ensures the pgvector extension is enabled (idempotent).
  2. Ensures the canonical Phase-1 IVFFlat index exists under the name
     memory_associative_embedding_idx (creates it only if absent).

Revision ID: 005
Revises: 9a1f2d0b6c7e
Create Date: 2026-04-15
"""

from __future__ import annotations

from typing import Sequence, Union

from alembic import op

revision: str = "005"
down_revision: Union[str, None] = "e04100e88ace"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    # Ensure pgvector extension is enabled (also done in 004, idempotent).
    op.execute("CREATE EXTENSION IF NOT EXISTS vector;")

    # Ensure the canonical Phase-1 IVFFlat index exists.
    # 004 may have created ix_memory_associative_embedding; this adds the
    # Phase-1 name memory_associative_embedding_idx if it is missing.
    op.execute(
        """
        DO $$
        BEGIN
            IF NOT EXISTS (
                SELECT 1
                FROM   pg_indexes
                WHERE  tablename  = 'memory_associative'
                  AND  indexname  = 'memory_associative_embedding_idx'
            ) THEN
                CREATE INDEX memory_associative_embedding_idx
                ON memory_associative
                USING ivfflat (embedding vector_cosine_ops)
                WITH  (lists = 100);
            END IF;
        END $$;
        """
    )


def downgrade() -> None:
    op.execute("DROP INDEX IF EXISTS memory_associative_embedding_idx;")