export declare function splitTopLevelComma(input: string): string[];
/**
 * Flattens key entries into one token per key part. An entry may hold several
 * comma-separated parts (`'id, toDate(ts)'`), but one that exactly names a
 * declared column is kept whole, since the name itself may contain a comma.
 */
export declare function normalizeKeyColumns(values: string[] | undefined, declaredColumns?: ReadonlySet<string>): string[];
/**
 * A key entry references a table column only when it is a bare identifier.
 * Anything else — function calls like `toDate(ts)`, arithmetic, or tuples — is
 * an expression that ClickHouse validates itself, so it must not be checked
 * against the table's declared column list.
 */
export declare function isPlainColumnReference(token: string): boolean;
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