/**
 * Compare expression tokens while preserving quoted values and identifier case.
 * SQL the lexer cannot read (e.g. an unterminated quote) falls back to its
 * normalizeSQLFragment form, encoded as a JSON string so it never equals a token
 * list.
 */
export declare function sqlExpressionFingerprint(value: string): string;
/**
 * Whether `expression` is the default ClickHouse stores for a bare EPHEMERAL
 * column. ClickHouse synthesizes defaultValueOfTypeName('<type as written>');
 * the literal keeps alias spellings (BIGINT, TEXT) that system.columns.type
 * canonicalizes, so any single string literal counts.
 */
export declare function isSyntheticEphemeralDefault(expression: string): boolean;
/**
 * Canonical one-line form of a SQL fragment: a view or materialized view `as`,
 * `partitionBy`, `ttl`, a skip index expression, a projection, a dictionary
 * `source`/`layout`/`lifetime`, or the same clauses read back from ClickHouse.
 *
 * Comments are dropped and every run of whitespace becomes one space, inside
 * string literals too. Comments must go before the newlines do: a `--`, `//`,
 * `# ` or `#!` comment ends at its newline, so on a single line it would swallow
 * the rest of the fragment and the `;` the renderer appends after it (#232).
 * Comment syntax is ClickHouse's, from the shared lexer: markers inside string
 * literals, quoted identifiers and heredocs are text, and an unterminated block
 * comment or string is kept as written for ClickHouse to report.
 *
 * A dropped comment leaves one space, so the tokens around it never fuse: a
 * minus, an empty block comment and a minus become `- -`, not a `--` comment.
 * Text without comments or a stray `#` normalizes exactly as a plain
 * whitespace collapse would, and the result is stable: normalizing it again
 * changes nothing.
 */
export declare function normalizeSQLFragment(value: string): string;
/**
 * SQL text without its comments, trimmed. Unlike normalizeSQLFragment, all
 * other text stays as written, including whitespace inside string literals.
 * chkit renders a column default expression on one line of a CREATE or ALTER
 * statement, where a `--` comment would swallow the `,`, `COMMENT`, `CODEC` or
 * `;` after it (#234).
 *
 * A run of whitespace and comments that holds a comment becomes one space, so
 * the tokens around it never fuse, or a newline after a stray `#`, for the
 * reason normalizeSQLFragment gives. A stray `#` at the end is followed by a
 * newline too: the ` COMMENT` or ` CODEC` rendered after it would otherwise
 * turn it into a `# ` comment that hides them. An unterminated block comment
 * or string is kept as written for ClickHouse to report.
 */
export declare function stripSQLComments(value: string): string;
export declare function normalizeEngine(engine: string): string;
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