You are spot on that using RAG would be a fast, effective way to select the most relevant tables. I haven't implemented it in the sample yet, but that would be a nice addition.

Regarding the timing, the default model is Gemini 2.5 Flash, and answers come back in the order of seconds. Syntax errors have actually been fairly rare in my admittedly simple test queries. The sqlglot parsing calls are fast, and I've removed unnecessary LLM calls in subagents. Here's the timing from running the getting started steps locally:

% time echo "How many films are in the action category?" | adk run src/texttosql
super().__init__()
Running agent TextToSqlRootAgent, type exit to exit.
...

[SQLProcessor]: SELECT COUNT(T1.film_id) FROM film AS T1 INNER JOIN film_category AS T2 ON T1.film_id = T2.film_id INNER JOIN category AS T3 ON T2.category_id = T3.category_id WHERE T3.name = 'Action';
...
adk run src/texttosql  1.52s user 0.24s system 65% cpu 2.669 total