File: stores/pg/src/vector/index.ts, line 1109-1113
What happens: describeIndex acquires a single client via this.pool.connect(), then uses Promise.all to run three queries simultaneously on that one client. The pg library only supports one in-flight query per client -- the second and third calls trigger the deprecation warning: "Calling client.query() when the client is already executing a query is deprecated and will be removed in pg@9.0."
When it fires: On startup, during the constructor's background cache warmup (cacheWarmupPromise), which calls getIndexInfo -> describeIndex for every existing vector index.
Suggested fix: Either run the three queries sequentially (await each), or use this.pool.query() instead of client.query() so the pool assigns separate connections for parallel execution.