Function plan_merge

nodedb-sql/src/planner/merge.rs:22–67

Plan a `MERGE INTO target USING source ON ... WHEN ... THEN ...` statement.

(stmt: &ast::Statement, catalog: &dyn SqlCatalog)

/// Plan a `MERGE INTO target USING source ON ... WHEN ... THEN ...` statement.
pub fn plan_merge(stmt: &ast::Statement, catalog: &dyn SqlCatalog) -> Result<Vec<SqlPlan>> {
    let ast::Statement::Merge(merge) = stmt else {
        return Err(SqlError::Parse {
            detail: "expected MERGE statement".into(),
        });
    };

    if merge.clauses.is_empty() {
        return Err(SqlError::Parse {
            detail: "MERGE statement requires at least one WHEN arm".into(),
        });
    }

    // ── Resolve target ──
    let (target_name, target_alias) = extract_table_factor_name_alias(&merge.table)?;
    // The ON clause uses the alias (or table name if no alias) as the qualifier.
    let target_ref = target_alias.as_deref().unwrap_or(target_name.as_str());
    let target_info = catalog
        .get_collection(DatabaseId::DEFAULT, &target_name)?
        .ok_or_else(|| SqlError::UnknownTable {
            name: target_name.clone(),
        })?;

    // ── Resolve source ──
    let source_plan = plan_merge_source(&merge.source, catalog)?;
    let source_alias = merge_source_alias(&merge.source, &source_plan);

    // ── Parse ON clause into equi-join columns ──
    let (target_join_col, source_join_col) =
        extract_merge_equijoin(&merge.on, target_ref, &source_alias)?;

    // ── Convert WHEN clauses ──
    let clauses = convert_merge_clauses(&merge.clauses, target_ref, &source_alias)?;

    // ── Dispatch to engine rules ──
    let rules = engine_rules::resolve_engine_rules(target_info.engine);
    rules.plan_merge(MergeParams {
        collection: target_name,
        source: Box::new(source_plan),
        target_join_col,
        source_join_col,
        source_alias,
        clauses,
        returning: false,
    })
}

// ── Source planning ────────────────────────────────────────────────────────