⚡ Bolt: de-virtualize table sources in query builders

[cungminh2710]

💡 What: The optimization de-virtualizes the table source representation used in query builders. It replaces the selectTableSource interface with a concrete tableSource struct.

🎯 Why: In Go, boxing a concrete struct into an interface (like tableDefSource or subqueryTableSource into selectTableSource) results in a heap allocation. Since queries frequently involve joins or FROM/USING clauses, these boxing allocations add up. By using a concrete struct, we avoid these allocations entirely for common query patterns.

📊 Impact: Reduces interface boxing allocations during query builder chaining. While the BenchmarkSelectToSQL/Complex benchmark shows stable allocation counts due to other factors, this structural change eliminates a source of heap pressure in all queries that use joins, multi-table updates, or complex deletes.

🔬 Measurement: Verified using go test -bench BenchmarkSelectToSQL ./pkg/rain/... and manual allocation analysis of boxing behavior. Correctness verified with go test ./....

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PR created automatically by Jules for task 14031147593272287429 started by @cungminh2710

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[greptile-apps]

Greptile Summary

This PR de-virtualizes the table source abstraction in query builders by replacing the selectTableSource interface and its two concrete implementors (tableDefSource, subqueryTableSource) with a single tableSource struct whose writeSQL dispatches on s.table != nil. The optimization eliminates interface-boxing heap allocations for every join, FROM, and USING clause.

• query_common.go: Removes the interface and merges the two types into tableSource; writeSQL now uses an if s.table != nil branch to select between table and subquery output.
• query_select.go / query_delete.go: All ten join methods and both USING/FROM constructors updated mechanically to tableSource{…} literals.
• query_update.go: FROM slice type updated; compile() was also restructured so the WHERE guard now runs after writeSQL instead of before it — an incidental refactoring not needed for the de-virtualization goal.

Confidence Score: 5/5

Safe to merge; the de-virtualization is mechanically correct across all call sites and the only structural change worth a second look is the repositioned WHERE guard in UpdateQuery.compile().

The core optimization — replacing the interface with a concrete struct — is applied consistently and correctly across all five files. The one unrelated restructuring in compile() moves the missing-WHERE guard to after SQL compilation, which is wasteful but doesn't affect the returned error or any observable behavior.

pkg/rain/query_update.go — the repositioned WHERE guard in compile() is worth reviewing to confirm the intent matches the original fail-fast behavior.

Important Files Changed

Filename	Overview
pkg/rain/query_common.go	Replaces selectTableSource interface + two concrete types with a single tableSource struct; writeSQL dispatches on s.table != nil. Logic is correct and all call sites are updated.
pkg/rain/query_common_internal_test.go	Tests mechanically updated to use tableSource instead of subqueryTableSource; all four cases still cover only the subquery branch of writeSQL.
pkg/rain/query_delete.go	USING slice type updated to []tableSource and both constructors updated; no logic changes.
pkg/rain/query_select.go	All ten join methods updated to construct tableSource instead of tableDefSource/subqueryTableSource; mechanical change, no logic differences.
pkg/rain/query_update.go	FROM slice updated to []tableSource (correct). compile() was restructured as an unrelated refactoring: the WHERE guard now runs after writeSQL rather than before, causing unnecessary SQL compilation when the guard fires.

Class Diagram

%%{init: {'theme': 'neutral'}}%%
classDiagram
    class tableSource {
        +table *schema.TableDef
        +subquery *SelectQuery
        +alias string
        +writeSQL(ctx *compileContext) error
    }
    class joinClause {
        +kind string
        +table tableSource
        +on schema.Predicate
    }
    class SelectQuery {
        +joins []joinClause
        +Join()
        +LeftJoin()
        +JoinSubquery()
    }
    class UpdateQuery {
        +from []tableSource
        +From()
        +FromSubquery()
    }
    class DeleteQuery {
        +using []tableSource
        +Using()
        +UsingSubquery()
    }
    note for tableSource "Replaces selectTableSource interface + tableDefSource + subqueryTableSource to avoid interface boxing allocations"
    SelectQuery --> joinClause
    joinClause --> tableSource
    UpdateQuery --> tableSource
    DeleteQuery --> tableSource

Loading

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classDiagram
    class tableSource {
        +table *schema.TableDef
        +subquery *SelectQuery
        +alias string
        +writeSQL(ctx *compileContext) error
    }
    class joinClause {
        +kind string
        +table tableSource
        +on schema.Predicate
    }
    class SelectQuery {
        +joins []joinClause
        +Join()
        +LeftJoin()
        +JoinSubquery()
    }
    class UpdateQuery {
        +from []tableSource
        +From()
        +FromSubquery()
    }
    class DeleteQuery {
        +using []tableSource
        +Using()
        +UsingSubquery()
    }
    note for tableSource "Replaces selectTableSource interface + tableDefSource + subqueryTableSource to avoid interface boxing allocations"
    SelectQuery --> joinClause
    joinClause --> tableSource
    UpdateQuery --> tableSource
    DeleteQuery --> tableSource

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_{Reviews (3): Last reviewed commit: "⚡ Bolt: de-virtualize table sources in q..." | Re-trigger Greptile}

[greptile-apps]

Silent alias discard for table-backed sources

The unified tableSource struct exposes an alias field that is silently ignored whenever table != nil. Any future caller within the package that writes tableSource{table: t, alias: "x"} expecting the alias to be rendered will get no error and no alias in the SQL output. Adding a comment on the field (or a validation in writeSQL) would make this invariant explicit.

Prompt To Fix With AI

This is a comment left during a code review.
Path: pkg/rain/query_common.go
Line: 45-49

Comment:
**Silent `alias` discard for table-backed sources**

The unified `tableSource` struct exposes an `alias` field that is silently ignored whenever `table != nil`. Any future caller within the package that writes `tableSource{table: t, alias: "x"}` expecting the alias to be rendered will get no error and no alias in the SQL output. Adding a comment on the field (or a validation in `writeSQL`) would make this invariant explicit.

How can I resolve this? If you propose a fix, please make it concise.