rawsql-ts
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[beta]High-performance SQL parser and AST analyzer written in TypeScript. Provides fast parsing and advanced transformation capabilities.
108 lines • 4.69 kB
JavaScript
import { WithClause } from "../models/Clause";
import { TokenType } from "../models/Lexeme";
import { SqlTokenizer } from "./SqlTokenizer";
import { CommonTableParser } from "./CommonTableParser";
/**
* Parser for SQL WITH clauses (Common Table Expressions - CTEs).
* Parses only the WITH clause portion of SQL, not the entire query.
*
* **Note**: For most use cases, use `SelectQueryParser` which provides more comprehensive SQL parsing.
* This parser should only be used for the special case where you need to analyze only the WITH clause portion.
*
* @example
* ```typescript
* // Parses only the WITH clause, not the following SELECT
* const sql = "WITH recursive_cte AS (SELECT 1 as n UNION SELECT n+1 FROM recursive_cte WHERE n < 10)";
* const withClause = WithClauseParser.parse(sql);
* console.log(withClause.recursive); // true
* console.log(withClause.tables.length); // 1
* ```
*/
export class WithClauseParser {
/**
* Parses a SQL string containing only a WITH clause into a WithClause AST.
* The input should contain only the WITH clause, not the subsequent main query.
*
* @param query - The SQL string containing only the WITH clause
* @returns The parsed WithClause object
* @throws Error if the syntax is invalid or there are unexpected tokens after the WITH clause
*
* @example
* ```typescript
* // Correct: Only the WITH clause
* const sql = "WITH users_data AS (SELECT id, name FROM users)";
* const withClause = WithClauseParser.parse(sql);
*
* // Error: Contains SELECT after WITH clause
* // const badSql = "WITH users_data AS (SELECT id, name FROM users) SELECT * FROM users_data";
* ```
*/
static parse(query) {
const tokenizer = new SqlTokenizer(query); // Initialize tokenizer
const lexemes = tokenizer.readLexmes(); // Get tokens
// Parse
const result = this.parseFromLexeme(lexemes, 0);
// Error if there are remaining tokens
if (result.newIndex < lexemes.length) {
throw new Error(`Syntax error: Unexpected token "${lexemes[result.newIndex].value}" at position ${result.newIndex}. The WITH clause is complete but there are additional tokens.`);
}
return result.value;
}
/**
* Parses a WITH clause from an array of lexemes starting at the specified index.
*
* @param lexemes - Array of lexemes to parse from
* @param index - Starting index in the lexemes array
* @returns Object containing the parsed WithClause and the new index position
* @throws Error if the syntax is invalid or WITH keyword is not found
*
* @example
* ```typescript
* const tokenizer = new SqlTokenizer("WITH cte AS (SELECT 1)");
* const lexemes = tokenizer.readLexmes();
* const result = WithClauseParser.parseFromLexeme(lexemes, 0);
* console.log(result.value.tables.length); // 1
* console.log(result.newIndex); // position after the WITH clause
* ```
*/
static parseFromLexeme(lexemes, index) {
let idx = index;
// Capture comments from the WITH keyword
const withTokenComments = idx < lexemes.length ? lexemes[idx].comments : null;
// Expect WITH keyword
if (idx < lexemes.length && lexemes[idx].value.toLowerCase() === "with") {
idx++;
}
else {
throw new Error(`Syntax error at position ${idx}: Expected WITH keyword.`);
}
// Check for RECURSIVE keyword
const recursive = idx < lexemes.length && lexemes[idx].value.toLowerCase() === "recursive";
if (recursive) {
idx++;
}
// Parse CTEs
const tables = [];
// Parse first CTE (required)
const firstCte = CommonTableParser.parseFromLexeme(lexemes, idx);
tables.push(firstCte.value);
idx = firstCte.newIndex;
// Parse additional CTEs (optional)
while (idx < lexemes.length && (lexemes[idx].type & TokenType.Comma)) {
idx++; // Skip comma
// Capture comments that may be before the next CTE name
// Check if there are tokens before the CTE name that might have comments
const cteResult = CommonTableParser.parseFromLexeme(lexemes, idx);
tables.push(cteResult.value);
idx = cteResult.newIndex;
}
// Create WITH clause with comments
const withClause = new WithClause(recursive, tables);
withClause.comments = withTokenComments;
return {
value: withClause,
newIndex: idx
};
}
}
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