ClickHouse/src/Parsers/TokenIterator.cpp

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#include <Parsers/TokenIterator.h>
namespace DB
{
const Token & Tokens::operator[](size_t index)
{
if (likely(index < data.size()))
return data[index];
while (data.empty() || !data.back().isEnd())
{
Token token = lexer.nextToken();
if (token.isSignificant())
{
data.emplace_back(std::move(token));
if (index < data.size())
return data[index];
}
}
return data.back();
}
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UnmatchedParentheses checkUnmatchedParentheses(TokenIterator begin)
{
/// We have just two kind of parentheses: () and [].
UnmatchedParentheses stack;
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/// We have to iterate through all tokens until the end to avoid false positive "Unmatched parentheses" error
/// when parser failed in the middle of the query.
for (TokenIterator it = begin; it.isValid(); ++it)
{
if (it->type == TokenType::OpeningRoundBracket || it->type == TokenType::OpeningSquareBracket)
{
stack.push_back(*it);
}
else if (it->type == TokenType::ClosingRoundBracket || it->type == TokenType::ClosingSquareBracket)
{
if (stack.empty())
{
/// Excessive closing bracket.
stack.push_back(*it);
return stack;
}
else if ((stack.back().type == TokenType::OpeningRoundBracket && it->type == TokenType::ClosingRoundBracket)
|| (stack.back().type == TokenType::OpeningSquareBracket && it->type == TokenType::ClosingSquareBracket))
{
/// Valid match.
stack.pop_back();
}
else
{
/// Closing bracket type doesn't match opening bracket type.
stack.push_back(*it);
return stack;
}
}
}
/// If stack is not empty, we have unclosed brackets.
return stack;
}
}