Bug Description

A clear and concise description of the bug.

Environment

• pg_textsearch: 0.5.1
• PostgreSQL: 18.3 (Postgres.app) on aarch64-apple-darwin23.6.0, compiled by Apple clang 15.0.0
• Platform: macOS, Apple Silicon (arm64)

Steps to Reproduce

Minimal reproduction

Any of these three sequences crash the server:

-- (1) ROLLBACK TO SAVEPOINT after BM25 scan
CREATE TEMP TABLE t (id serial, body text);
INSERT INTO t VALUES (DEFAULT, 'hello world'), (DEFAULT, 'foo bar baz');
CREATE INDEX t_idx ON t USING bm25(body) WITH (text_config = 'english');
SAVEPOINT sp1;
SELECT body <@> 'hello' FROM t LIMIT 1;
ROLLBACK TO SAVEPOINT sp1;   -- server crashes here

-- (2) Plain ROLLBACK after BM25 scan (same result)
BEGIN;
CREATE TEMP TABLE t2 (id serial, body text);
INSERT INTO t2 VALUES (DEFAULT, 'hello world');
CREATE INDEX t2_idx ON t2 USING bm25(body) WITH (text_config = 'english');
SELECT body <@> 'hello' FROM t2 LIMIT 1;
ROLLBACK;                     -- server crashes here

Expected Behavior

Server to not crash.

Actual Behavior

Result in both cases:

server closed the connection unexpectedly
  This probably means the server terminated abnormally
  before or while processing the request.
connection to server was lost

Secondary effects

1. Connection corruption in application code — when psycopg3 uses a nested transaction (savepoint) to isolate the BM25 query, it logs ResourceOwnerEnlarge called
   after release started during the savepoint rollback before the crash fully propagates. The connection ends up in [INERROR] state, is returned to the pool, and the
   pool's rollback attempt also fails — discarding the connection and returning a 500 to the client.
2. Index TOAST corruption after repeated crashes — after the server crashes, subsequent queries against the index fail with:
   INFO: Recovering pg_textsearch index NNNN from disk
   ERROR: missing chunk number 2 for toast value NNNNN in pg_toast_NNNNN
3. The index must be dropped and recreated (DROP INDEX … ; CREATE INDEX … USING bm25 …).

Additional Context

n/a