xb

Custom JOINs Guide (English)

English version of xb/doc/CUSTOM_JOINS_GUIDE.md. It explains how to extend xb’s JOIN DSL for dialect-specific syntax such as ClickHouse GLOBAL JOIN or ASOF JOIN.

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Built-in JOIN catalog

const (
    inner_join      = "INNER JOIN"
    left_join       = "LEFT JOIN"
    right_join      = "RIGHT JOIN"
    cross_join      = "CROSS JOIN"
    asof_join       = "ASOF JOIN"
    global_join     = "GLOBAL JOIN"
    full_outer_join = "FULL OUTER JOIN"
)

Use FromX(func(*FromBuilder)) with JOIN(kind) helpers to compose multi-step pipelines.

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Adding your own JOIN

func LATERAL() xb.JOIN {
    return func() string {
        return "LATERAL JOIN"
    }
}

• Return a closure so the builder can call it lazily.
• Register short helper methods (func (fb *FromBuilder) Lateral(...)) if you need extra configuration.

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Best practices

• Keep JOIN helpers pure; they should only format SQL keywords.
• Reuse Cond(func(*ON)) to define predicates; this keeps auto-filtering intact.
• For dialect-specific hints (GLOBAL, FINAL, etc.) expose them via FromX configuration so the rest of the chain stays portable.

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Examples

• Multi-join pipeline mixing subqueries and ON clauses.
• Custom join that injects optimizer hints.
• Cross-shard join that enforces tenant filters inside every ON block.

Refer to doc/en/BUILDER_BEST_PRACTICES.md for more patterns.

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