feat(backend): search finds word prefixes, earlier versions and deleted messages, with filters and cursor paging

backend/migrations/versions/d8f1a6c3e5b7_message_search.py

@@ -0,0 +1,138 @@
+"""message search index outside the hypertable, versions searchable
+
+Revision ID: d8f1a6c3e5b7
+Revises: c9e2a7f4b1d8
+Create Date: 2026-10-19 03:00:00.000000
+
+"""
+
+from collections.abc import Sequence
+
+from alembic import op
+
+revision: str = "d8f1a6c3e5b7"
+down_revision: str | None = "c9e2a7f4b1d8"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+_VECTOR = """
+CREATE FUNCTION search_vector(body text) RETURNS tsvector
+LANGUAGE sql IMMUTABLE PARALLEL SAFE AS $$
+    SELECT to_tsvector('russian', translate(coalesce(body, ''), 'Ёё', 'Ее'))
+        || to_tsvector('simple', translate(coalesce(body, ''), 'Ёё', 'Ее'))
+$$
+"""
+
+_TABLE = """
+CREATE TABLE message_search (
+    account_id integer NOT NULL,
+    chat_id bigint NOT NULL,
+    message_id bigint NOT NULL,
+    date timestamptz NOT NULL,
+    sender_id bigint,
+    text text,
+    has_media boolean NOT NULL DEFAULT false,
+    edited_at timestamptz,
+    deleted_at timestamptz,
+    tsv tsvector GENERATED ALWAYS AS (search_vector(text)) STORED,
+    PRIMARY KEY (account_id, chat_id, message_id, date)
+)
+"""
+
+_BACKFILL = """
+INSERT INTO message_search (account_id, chat_id, message_id, date, sender_id,
+                            text, has_media, edited_at, deleted_at)
+SELECT account_id, chat_id, message_id, date, sender_id,
+       text, has_media, edited_at, deleted_at
+FROM messages
+"""
+
+_SYNC = """
+CREATE FUNCTION message_search_sync() RETURNS trigger LANGUAGE plpgsql AS $$
+BEGIN
+    IF TG_OP = 'DELETE' THEN
+        DELETE FROM message_search
+        WHERE account_id = OLD.account_id AND chat_id = OLD.chat_id
+          AND message_id = OLD.message_id AND date = OLD.date;
+        RETURN NULL;
+    END IF;
+    INSERT INTO message_search (account_id, chat_id, message_id, date,
+                                sender_id, text, has_media, edited_at,
+                                deleted_at)
+    VALUES (NEW.account_id, NEW.chat_id, NEW.message_id, NEW.date,
+            NEW.sender_id, NEW.text, NEW.has_media, NEW.edited_at,
+            NEW.deleted_at)
+    ON CONFLICT (account_id, chat_id, message_id, date) DO UPDATE SET
+        sender_id = EXCLUDED.sender_id,
+        text = EXCLUDED.text,
+        has_media = EXCLUDED.has_media,
+        edited_at = EXCLUDED.edited_at,
+        deleted_at = EXCLUDED.deleted_at;
+    RETURN NULL;
+END;
+$$
+"""
+
+_CHANGED = (
+    "OLD.text IS DISTINCT FROM NEW.text "
+    "OR OLD.sender_id IS DISTINCT FROM NEW.sender_id "
+    "OR OLD.has_media IS DISTINCT FROM NEW.has_media "
+    "OR OLD.edited_at IS DISTINCT FROM NEW.edited_at "
+    "OR OLD.deleted_at IS DISTINCT FROM NEW.deleted_at"
+)
+
+
+def upgrade() -> None:
+    op.execute(_VECTOR)
+    op.execute(_TABLE)
+    op.execute(_BACKFILL)
+    op.execute("CREATE INDEX ix_message_search_tsv ON message_search USING gin (tsv)")
+    op.execute(
+        "CREATE INDEX ix_message_search_recent ON message_search "
+        "(account_id, date DESC, chat_id DESC, message_id DESC)"
+    )
+    op.execute(
+        "CREATE INDEX ix_message_search_sender ON message_search "
+        "(account_id, sender_id, date DESC)"
+    )
+    op.execute(_SYNC)
+    op.execute(
+        "CREATE TRIGGER messages_search_insert AFTER INSERT ON messages "
+        "FOR EACH ROW EXECUTE FUNCTION message_search_sync()"
+    )
+    op.execute(
+        "CREATE TRIGGER messages_search_update AFTER UPDATE ON messages "
+        f"FOR EACH ROW WHEN ({_CHANGED}) EXECUTE FUNCTION message_search_sync()"
+    )
+    op.execute(
+        "CREATE TRIGGER messages_search_delete AFTER DELETE ON messages "
+        "FOR EACH ROW EXECUTE FUNCTION message_search_sync()"
+    )
+    op.execute(
+        "CREATE INDEX ix_message_versions_tsv ON message_versions USING gin "
+        "(search_vector(text))"
+    )
+    op.execute("DROP INDEX IF EXISTS ix_media_tsv")
+    op.execute(
+        "CREATE INDEX ix_media_tsv ON media USING gin (search_vector(extracted_text))"
+    )
+    op.execute("DROP INDEX IF EXISTS ix_messages_tsv")
+
+
+def downgrade() -> None:
+    op.execute(
+        "CREATE INDEX ix_messages_tsv ON messages USING gin "
+        "(to_tsvector('russian', coalesce(text, '')))"
+    )
+    op.execute("DROP INDEX IF EXISTS ix_media_tsv")
+    op.execute(
+        "CREATE INDEX ix_media_tsv ON media USING gin "
+        "(to_tsvector('russian', coalesce(extracted_text, '')))"
+    )
+    op.execute("DROP INDEX IF EXISTS ix_message_versions_tsv")
+    op.execute("DROP TRIGGER IF EXISTS messages_search_delete ON messages")
+    op.execute("DROP TRIGGER IF EXISTS messages_search_update ON messages")
+    op.execute("DROP TRIGGER IF EXISTS messages_search_insert ON messages")
+    op.execute("DROP FUNCTION IF EXISTS message_search_sync()")
+    op.execute("DROP TABLE IF EXISTS message_search")
+    op.execute("DROP FUNCTION IF EXISTS search_vector(text)")