rawsql-ts
Version:
[beta]High-performance SQL parser and AST analyzer written in TypeScript. Provides fast parsing and advanced transformation capabilities.
109 lines • 4.56 kB
JavaScript
import { Distinct, DistinctOn, SelectClause, SelectItem } from "../models/Clause";
import { TokenType } from "../models/Lexeme";
import { ColumnReference } from "../models/ValueComponent";
import { SqlTokenizer } from "./SqlTokenizer";
import { ValueParser } from "./ValueParser";
export class SelectClauseParser {
// Parse SQL string to AST (was: parse)
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 SELECT clause is complete but there are additional tokens.`);
}
return result.value;
}
// Parse from lexeme array (was: parse)
static parseFromLexeme(lexemes, index) {
let idx = index;
let distinct = null;
if (lexemes[idx].value !== 'select') {
throw new Error(`Syntax error at position ${idx}: Expected 'SELECT' keyword but found "${lexemes[idx].value}". SELECT clauses must start with the SELECT keyword.`);
}
idx++;
if (idx < lexemes.length && lexemes[idx].value === 'distinct') {
idx++;
distinct = new Distinct();
}
else if (idx < lexemes.length && lexemes[idx].value === 'distinct on') {
idx++;
const argument = ValueParser.parseArgument(TokenType.OpenParen, TokenType.CloseParen, lexemes, idx);
distinct = new DistinctOn(argument.value);
idx = argument.newIndex;
}
const items = [];
const item = SelectItemParser.parseItem(lexemes, idx);
items.push(item.value);
idx = item.newIndex;
while (idx < lexemes.length && (lexemes[idx].type & TokenType.Comma)) {
idx++;
const item = SelectItemParser.parseItem(lexemes, idx);
items.push(item.value);
idx = item.newIndex;
}
if (items.length === 0) {
throw new Error(`Syntax error at position ${index}: No select items found. The SELECT clause requires at least one expression to select.`);
}
else {
const clause = new SelectClause(items, distinct);
return { value: clause, newIndex: idx };
}
}
}
// Extracted SelectItemParser for parsing individual select items
export class SelectItemParser {
/**
* Parses a single select item from a SQL string.
* @param query The SQL string representing a select item (e.g. 'id as user_id').
* @returns The parsed SelectItem instance.
*/
static parse(query) {
const tokenizer = new SqlTokenizer(query);
const lexemes = tokenizer.readLexmes();
const result = this.parseItem(lexemes, 0);
if (result.newIndex < lexemes.length) {
throw new Error(`Syntax error: Unexpected token "${lexemes[result.newIndex].value}" at position ${result.newIndex}. The select item is complete but there are additional tokens.`);
}
return result.value;
}
/**
* Parses a single select item from lexemes.
* @param lexemes The array of lexemes.
* @param index The starting index.
* @returns An object containing the SelectItem and the new index.
*/
static parseItem(lexemes, index) {
let idx = index;
const parsedValue = ValueParser.parseFromLexeme(lexemes, idx);
const value = parsedValue.value;
idx = parsedValue.newIndex;
if (idx < lexemes.length && lexemes[idx].value === 'as') {
// Skip 'AS' keyword
idx++;
}
if (idx < lexemes.length && (lexemes[idx].type & TokenType.Identifier)) {
const alias = lexemes[idx].value;
idx++;
return {
value: new SelectItem(value, alias),
newIndex: idx,
};
}
else if (value instanceof ColumnReference && value.column.name !== "*") {
// nameless select item
return {
value: new SelectItem(value, value.column.name),
newIndex: idx,
};
}
// nameless select item
return {
value: new SelectItem(value),
newIndex: idx,
};
}
}
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