fix: translate named parameters for PostgreSQL

[olavloite]

Named parameters in the SQL string were not translated to PostgreSQL-style query parameters before sending these to Spanner. This made it impossible to use named query parameters with PostgreSQL-dialect databases.

This change also fixes an issue that PostgreSQL-style query parameters had to be used in order, and an issue that using a wrong value for a named parameter would not cause an error, and instead just silently send a null value for the parameter to Spanner.

Fixes #738
Fixes #601
Fixes #730

[gemini-code-assist]

Summary of Changes

Hello @olavloite, 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 enhances the handling of SQL query parameters, particularly for PostgreSQL-dialect databases. It introduces the capability to correctly translate named parameters into the PostgreSQL-specific indexed format, which was previously a blocker for using named parameters with this dialect. Furthermore, it improves parameter validation by explicitly erroring on missing named parameter values instead of silently substituting nulls, and relaxes the ordering requirement for PostgreSQL-style parameters. The changes also enforce a single parameter style per statement to maintain clarity and prevent unexpected behavior.

Highlights

• PostgreSQL Named Parameter Translation: Implemented the translation of named parameters (e.g., @param) in SQL queries to PostgreSQL-style indexed parameters (e.g., $1) when using a PostgreSQL-dialect database. This enables the use of named parameters which were previously unsupported.
• Improved Parameter Validation: Fixed an issue where providing an incorrect named parameter value would silently result in a null value being sent to Spanner. The system now correctly returns an InvalidArgument error in such cases, preventing silent data issues.
• Flexible PostgreSQL Parameter Ordering: Resolved a limitation where PostgreSQL-style query parameters previously had to be used in sequential order. They can now be provided in any order, improving usability.
• Enforced Single Parameter Style: Added validation to ensure that SQL statements do not mix different parameter styles (named, positional, or indexed) within a single query. This prevents ambiguity and potential errors.

Changelog

• conn.go
  • Updated PrepareContext to correctly receive and utilize the new namedParamsToIndexedParam map from the parser.
  • Ensured that the original SQL query string is retained for statement preparation, rather than the potentially modified string from parameter parsing, to maintain consistency.
• driver_with_mockserver_test.go
  • Corrected test assertions and comments in TestQueryWithReusedPositionalParameter to reflect accurate parameter values.
• parser/statement_parser.go
  • Introduced maps package for map operations.
  • Extended statementsCacheEntry to store the namedParamsToIndexedParam map for caching PostgreSQL parameter translations.
  • Added engineSupportsNamedParametersWithPrefix to abstract dialect-specific parameter prefix rules.
  • Modified ParseParameters to return the new namedParamsToIndexedParam map, specifically for PostgreSQL dialect.
  • Refactored calculateFindParamsResult to implement the translation logic for named parameters to PostgreSQL indexed parameters, manage parameter style conflicts, and update caching mechanisms.
  • Implemented strict validation to disallow mixing of named, positional, and indexed parameter styles within a single SQL statement.
• stmt.go
  • Added fmt and strconv imports.
  • Modified prepareSpannerStmt to process the namedParamsToIndexedParam map, translating internal parameter names back to their original named form for error messages.
  • Enhanced error messages for missing parameters to display the user-friendly named parameter (e.g., @id) instead of the internal p1 representation.
• stmt_with_mockserver_test.go
  • Added imports for database/sql and databasepb.
  • Introduced TestMissingNamedParam to specifically test the new error handling for missing named parameters.
  • Created a paramTest struct and wantErrOrExecErr helper to streamline parameter test definitions.
  • Added comprehensive test suites (TestPositionalParametersWithGoogleSQL, TestNamedParametersWithGoogleSQL, TestIndexedParametersWithPG, TestNamedParametersWithPG, TestPositionalParametersWithPG) to validate parameter parsing, translation, and error handling across different dialects and parameter styles.

Activity

• The author, olavloite, initiated this pull request to address several long-standing issues related to SQL parameter handling, as indicated by the referenced issues PostgreSQL positional argument must be used in order #738, Support named parameters with PostgreSQL-dialect databases #601, and fix: validate named parameters are present in arguments #730.
• The changes involve significant refactoring of the SQL parser and statement preparation logic, along with the addition of extensive new test cases to ensure correctness and prevent regressions.

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[gemini-code-assist]

Code Review

This pull request introduces a fix for translating named parameters for PostgreSQL-dialect databases. The changes correctly handle the translation of @name style parameters to PostgreSQL's $n style, fix an issue with out-of-order parameter usage, and ensure that an error is thrown for missing named parameters instead of silently sending a null value. The implementation involves significant updates to the SQL statement parser, including a new parameter translation mechanism and more robust validation of parameter styles. The accompanying tests are comprehensive and cover a wide range of scenarios for both GoogleSQL and PostgreSQL dialects, providing strong confidence in the correctness of the solution. The changes are well-structured and I have no further suggestions for improvement.

[olavloite]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a significant and well-implemented fix for handling named parameters in PostgreSQL-dialect databases. The changes correctly translate named parameters to PostgreSQL-style parameters, address issues with parameter ordering, and improve error handling for missing parameters. The logic is complex but appears correct, and it is backed by a comprehensive set of new tests that cover various scenarios and edge cases. The code is clean and the changes are consistent across the affected files. Overall, this is a high-quality contribution that improves the usability and correctness of the Spanner driver for PostgreSQL users.

[bhatt4982]

LGTM...