Add aggregate function support to BigQuery query_table API

[wbssbw]

Summary

Extends the query_table BigQuery API to support aggregate column functions (COUNT, MAX, MIN).
Previously, columns were plain strings; they are now typed Column structs that carry an optional ColumnFunction.
When a function is specified, the generated SQL wraps the column identifier accordingly (e.g., COUNT(col)).

Changes

Code

• runtime/plaid-stl/src/gcp/bigquery.rs: Added Column struct with identifier: String and function: Option<ColumnFunction>; added ColumnFunction enum (Count, Max, Min) with Display impl; updated QueryTableRequest.columns from Vec<String> to Vec<Column>; updated query_table signature to accept Vec<Column>.
• runtime/plaid/src/apis/gcp/bigquery.rs: Updated build_query_string parameter from &[String] to &[Column]; identifier validation and column-list construction now read col.identifier and optionally emit FUNCTION(identifier) syntax.

Rationale

Aggregate functions are a common need when querying tables. Encoding the function in the column type keeps the query-building logic centralized and validated server-side, avoiding raw SQL injection risks from caller-supplied function strings.

Security Considerations

Identifier validation now operates on col.identifier as before, ensuring that only allowlisted or validated identifiers pass through. The ColumnFunction enum is a closed set of known-safe SQL keywords rendered via Display, so no user-supplied function names reach the generated SQL. No authentication or authorization surface changes.

Breaking Changes

query_table and QueryTableRequest now require Vec<Column> instead of Vec<String> / impl Iterator<Item = impl Display>. Callers must be updated to construct Column values; a plain column with no function is Column { identifier: "col".into(), function: None }.

[Copilot]

Pull request overview

Extends the BigQuery query_table API to allow selecting aggregate column functions (COUNT, MAX, MIN) by introducing a typed Column model (identifier + optional function) and updating SQL generation accordingly.

Changes:

• Introduced Column and ColumnFunction in plaid-stl, and changed QueryTableRequest.columns to Vec<Column>.
• Updated the runtime BigQuery API to validate Column.identifier and render FUNCTION(\identifier`)` when a function is present.
• Updated the runtime result-mapping loop to iterate over Column values instead of raw strings.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated 4 comments.

File	Description
runtime/plaid/src/apis/gcp/bigquery.rs	Accepts Column inputs, validates identifiers via Column.identifier, and renders aggregate function syntax in generated SQL.
runtime/plaid-stl/src/gcp/bigquery.rs	Adds the Column / ColumnFunction request types and updates the public query_table API surface to use them.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 6 changed files in this pull request and generated 1 comment.