impl(bigtable): improve query execution refresh and retry

[scotthart]

• Introduces separate retry traits, policy, and option, QueryPlanRefreshFunctionRetry, for query plan refresh attempts which have a broader definition of transient errors.
• Renames QueryPlanRefreshRetry to ExecuteQueryPlanRefreshRetry to be more precise and differentiate it from QueryPlanRefreshFunctionRetry.
• Adds a wrapper class, QueryPlanRefreshingPartialResultSource, that handles the query plan refresh logic and recreating the PartialResultSource if necessary depending on when in the stream creation/processing the query plan refresh is indicated.
• Updated PartialResultSetSouce::resume_token_ documentation to match Bigtable implementation.
• Enables all the Bigtable ExecuteQuery conformance tests that we currently plan to support.

[gemini-code-assist]

Summary of Changes

Hello @scotthart, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the robustness and clarity of Bigtable's query execution by enhancing its query plan refresh and retry mechanisms. It introduces a more granular approach to handling transient errors during query plan refreshes and centralizes the refresh logic within a dedicated class. These changes lead to a more resilient system, better organized code, and expanded test coverage for Bigtable's ExecuteQuery functionality.

Highlights

• Refined Query Plan Refresh Retry Policies: Introduced a new, distinct retry trait, policy, and option (QueryPlanRefreshFunctionRetry) specifically for internal query plan refresh attempts, allowing for a broader definition of transient errors (including kInternal). The existing query plan refresh retry mechanism has been renamed to ExecuteQueryPlanRefreshRetry for clarity, differentiating between the overall query execution retry and the internal refresh function's retry.
• Centralized Query Plan Refresh Logic: A new wrapper class, QueryPlanRefreshingPartialResultSource, has been added to encapsulate and manage the complex logic for query plan refreshing and the recreation of PartialResultSource instances. This streamlines the ExecuteQuery implementation by abstracting the retry loop and refresh handling.
• Enhanced Conformance Test Coverage: More Bigtable ExecuteQuery conformance tests have been enabled, indicating improved stability and correctness of the query execution and refresh mechanisms. This expands the scope of supported scenarios and ensures better adherence to Bigtable's expected behavior.
• Updated resume_token_ Documentation: The documentation for PartialResultSetSource::resume_token_ has been updated to accurately reflect the Bigtable implementation details, providing clearer guidance on its purpose and behavior during query resumption and retries.

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[gemini-code-assist]

Code Review

This pull request significantly improves the query execution and retry logic. The introduction of the QueryPlanRefreshingPartialResultSource class is a great refactoring that encapsulates the complex logic for handling query plan refreshes, making the ExecuteQuery method much cleaner. The renaming of various policies and traits for clarity, and the addition of a separate retry policy for the query plan refresh function, are also welcome improvements. The changes look solid and improve the robustness and maintainability of the code. I have a couple of minor suggestions for improving code style and consistency.

[diegomarquezp]

I suspected there was a better place for this check. How is it being handled now?

[scotthart]

It's part of the different Retry traits defined in retry_traits.h. Unfortunately, refreshing query plans as part of streaming the query results requires a total of 3 different retry traits depending on what operation is occurring.

[codecov]

Codecov Report

❌ Patch coverage is 74.82517% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.94%. Comparing base (45fe5af) to head (a3347de).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ogle/cloud/bigtable/tests/data_integration_test.cc	0.00%	18 Missing ⚠️
google/cloud/bigtable/internal/retry_traits.h	0.00%	7 Missing ⚠️
...le/cloud/bigtable/internal/data_connection_impl.cc	92.40%	6 Missing ⚠️
google/cloud/bigtable/retry_policy.h	76.92%	3 Missing ⚠️
...oud/bigtable/internal/partial_result_set_source.cc	71.42%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15788      +/-   ##
==========================================
- Coverage   92.94%   92.94%   -0.01%     
==========================================
  Files        2454     2454              
  Lines      226878   226946      +68     
==========================================
+ Hits       210879   210933      +54     
- Misses      15999    16013      +14     

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