Spanner: PostgreSQL Dialect

[azulzaietz]

Describe the bug
When running commands against Spanner Database with PostgreSQL dialect, the tool returns an unclear error related to backticks (works fine for Spanner databases with GoogleSQL dialect).

What version of DVT are you using?
Ex: 8.5.2

What type of connections are you using for source and target?
AlloyDB for source, Spanner with PostgreSQL dialect for target

Steps to reproduce the behavior
1.

data-validation connections add --connection-name alloydb Postgres \
  --host 10.30.0.25 \
  --port 5432 \
  --user postgres \
  --password alloydb123 \
  --database test_v2

data-validation connections add \
--connection-name spanner Spanner \ 
--project-id reve-ai-26 \ 
--instance-id nodes-test \ 
--database-id postgres_2026-03-26_1607-774c

data-validation validate custom-query row -sc alloydb -tc spanner --source-query "SELECT * FROM public.my_table_01 LIMIT 50" --target-query "SELECT * FROM my_table_01 LIMIT 50" --primary-keys id --hash '*'

4. See error

Traceback (most recent call last):
  File "/home/admin_azulz_altostrat_com/venv/lib/python3.11/site-packages/google/api_core/grpc_helpers.py", line 149, in error_remapped_callable
    return _StreamingResponseIterator(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/admin_azulz_altostrat_com/venv/lib/python3.11/site-packages/google/api_core/grpc_helpers.py", line 71, in __init__
    self._stored_first_result = next(self._wrapped)
                                ^^^^^^^^^^^^^^^^^^^
  File "/home/admin_azulz_altostrat_com/venv/lib/python3.11/site-packages/grpc/_channel.py", line 538, in __next__
    return self._next()
           ^^^^^^^^^^^^
  File "/home/admin_azulz_altostrat_com/venv/lib/python3.11/site-packages/grpc/_channel.py", line 956, in _next
    raise self
grpc._channel._MultiThreadedRendezvous: <_MultiThreadedRendezvous of RPC that terminated with:
        status = StatusCode.INVALID_ARGUMENT
        details = "[ERROR] syntax error at or near "`""
        debug_error_string = "UNKNOWN:Error received from peer ipv4:74.125.135.95:443 {grpc_message:"[ERROR] syntax error at or near \"`\"", grpc_status:3}"
>

Screenshots

How are you executing DVT?
CLI commands on VM

Additional context
I believe this is occurring because DVT is configured to generate only GoogleSQL queries, which use backticks, while the PostgreSQL dialect does not support them