ClickHouse/dbms/Interpreters/CollectJoinOnKeysVisitor.cpp

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#include <Parsers/queryToString.h>
#include <Interpreters/CollectJoinOnKeysVisitor.h>
#include <Interpreters/IdentifierSemantic.h>
#include <Interpreters/AnalyzedJoin.h>
namespace DB
{
namespace ErrorCodes
{
extern const int INVALID_JOIN_ON_EXPRESSION;
extern const int AMBIGUOUS_COLUMN_NAME;
extern const int LOGICAL_ERROR;
}
void CollectJoinOnKeysMatcher::Data::addJoinKeys(const ASTPtr & left_ast, const ASTPtr & right_ast,
const std::pair<size_t, size_t> & table_no)
{
ASTPtr left = left_ast->clone();
ASTPtr right = right_ast->clone();
if (table_no.first == 1 || table_no.second == 2)
analyzed_join.addOnKeys(left, right);
else if (table_no.first == 2 || table_no.second == 1)
analyzed_join.addOnKeys(right, left);
else
throw Exception("Cannot detect left and right JOIN keys. JOIN ON section is ambiguous.",
ErrorCodes::AMBIGUOUS_COLUMN_NAME);
has_some = true;
}
void CollectJoinOnKeysMatcher::Data::addAsofJoinKeys(const ASTPtr & left_ast, const ASTPtr & right_ast,
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const std::pair<size_t, size_t> & table_no, const ASOF::Inequality & inequality)
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{
if (table_no.first == 1 || table_no.second == 2)
{
asof_left_key = left_ast->clone();
asof_right_key = right_ast->clone();
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analyzed_join.setAsofInequality(inequality);
}
else if (table_no.first == 2 || table_no.second == 1)
{
asof_left_key = right_ast->clone();
asof_right_key = left_ast->clone();
analyzed_join.setAsofInequality(ASOF::reverseInequality(inequality));
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}
}
void CollectJoinOnKeysMatcher::Data::asofToJoinKeys()
{
if (!asof_left_key || !asof_right_key)
throw Exception("No inequality in ASOF JOIN ON section.", ErrorCodes::INVALID_JOIN_ON_EXPRESSION);
addJoinKeys(asof_left_key, asof_right_key, {1, 2});
}
void CollectJoinOnKeysMatcher::visit(const ASTFunction & func, const ASTPtr & ast, Data & data)
{
if (func.name == "and")
return; /// go into children
if (func.name == "equals")
{
ASTPtr left = func.arguments->children.at(0);
ASTPtr right = func.arguments->children.at(1);
auto table_numbers = getTableNumbers(ast, left, right, data);
data.addJoinKeys(left, right, table_numbers);
return;
}
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ASOF::Inequality inequality = ASOF::getInequality(func.name);
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if (data.is_asof && (inequality != ASOF::Inequality::None))
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{
if (data.asof_left_key || data.asof_right_key)
throwSyntaxException("ASOF JOIN expects exactly one inequality in ON section, unexpected " + queryToString(ast) + ".");
ASTPtr left = func.arguments->children.at(0);
ASTPtr right = func.arguments->children.at(1);
auto table_numbers = getTableNumbers(ast, left, right, data);
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data.addAsofJoinKeys(left, right, table_numbers, inequality);
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return;
}
throwSyntaxException("Expected equals expression, got " + queryToString(ast) + ".");
}
void CollectJoinOnKeysMatcher::getIdentifiers(const ASTPtr & ast, std::vector<const ASTIdentifier *> & out)
{
if (const auto * ident = ast->as<ASTIdentifier>())
{
if (IdentifierSemantic::getColumnName(*ident))
out.push_back(ident);
return;
}
for (const auto & child : ast->children)
getIdentifiers(child, out);
}
std::pair<size_t, size_t> CollectJoinOnKeysMatcher::getTableNumbers(const ASTPtr & expr, const ASTPtr & left_ast, const ASTPtr & right_ast,
Data & data)
{
std::vector<const ASTIdentifier *> left_identifiers;
std::vector<const ASTIdentifier *> right_identifiers;
getIdentifiers(left_ast, left_identifiers);
getIdentifiers(right_ast, right_identifiers);
size_t left_idents_table = getTableForIdentifiers(left_identifiers, data);
size_t right_idents_table = getTableForIdentifiers(right_identifiers, data);
if (left_idents_table && left_idents_table == right_idents_table)
{
auto left_name = queryToString(*left_identifiers[0]);
auto right_name = queryToString(*right_identifiers[0]);
throwSyntaxException("In expression " + queryToString(expr) + " columns " + left_name + " and " + right_name
+ " are from the same table but from different arguments of equal function.");
}
return std::make_pair(left_idents_table, right_idents_table);
}
const ASTIdentifier * CollectJoinOnKeysMatcher::unrollAliases(const ASTIdentifier * identifier, const Aliases & aliases)
{
if (identifier->compound())
return identifier;
UInt32 max_attempts = 100;
for (auto it = aliases.find(identifier->name); it != aliases.end();)
{
const ASTIdentifier * parent = identifier;
identifier = it->second->as<ASTIdentifier>();
if (!identifier)
break; /// not a column alias
if (identifier == parent)
break; /// alias to itself with the same name: 'a as a'
if (identifier->compound())
break; /// not an alias. Break to prevent cycle through short names: 'a as b, t1.b as a'
it = aliases.find(identifier->name);
if (!max_attempts--)
throw Exception("Cannot unroll aliases for '" + identifier->name + "'", ErrorCodes::LOGICAL_ERROR);
}
return identifier;
}
/// @returns 1 if identifiers belongs to left table, 2 for right table and 0 if unknown. Throws on table mix.
/// Place detected identifier into identifiers[0] if any.
size_t CollectJoinOnKeysMatcher::getTableForIdentifiers(std::vector<const ASTIdentifier *> & identifiers, const Data & data)
{
size_t table_number = 0;
for (auto & ident : identifiers)
{
const ASTIdentifier * identifier = unrollAliases(ident, data.aliases);
if (!identifier)
continue;
/// Column name could be cropped to a short form in TranslateQualifiedNamesVisitor.
/// In this case it saves membership in IdentifierSemantic.
auto opt = IdentifierSemantic::getMembership(*identifier);
size_t membership = opt ? (*opt + 1) : 0;
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if (!membership)
{
const String & name = identifier->name;
bool in_left_table = data.left_table.hasColumn(name);
bool in_right_table = data.right_table.hasColumn(name);
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if (in_left_table && in_right_table)
{
/// Relax ambiguous check for multiple JOINs
if (auto original_name = IdentifierSemantic::uncover(*identifier))
{
auto match = IdentifierSemantic::canReferColumnToTable(*original_name, data.right_table.table);
if (match == IdentifierSemantic::ColumnMatch::NoMatch)
in_right_table = false;
in_left_table = !in_right_table;
}
else
throw Exception("Column '" + name + "' is ambiguous", ErrorCodes::AMBIGUOUS_COLUMN_NAME);
}
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if (in_left_table)
membership = 1;
if (in_right_table)
membership = 2;
}
if (membership && table_number == 0)
{
table_number = membership;
std::swap(ident, identifiers[0]); /// move first detected identifier to the first position
}
if (membership && membership != table_number)
{
throw Exception("Invalid columns in JOIN ON section. Columns "
+ identifiers[0]->getAliasOrColumnName() + " and " + ident->getAliasOrColumnName()
+ " are from different tables.", ErrorCodes::INVALID_JOIN_ON_EXPRESSION);
}
}
return table_number;
}
[[noreturn]] void CollectJoinOnKeysMatcher::throwSyntaxException(const String & msg)
{
throw Exception("Invalid expression for JOIN ON. " + msg +
" Supported syntax: JOIN ON Expr([table.]column, ...) = Expr([table.]column, ...) "
"[AND Expr([table.]column, ...) = Expr([table.]column, ...) ...]",
ErrorCodes::INVALID_JOIN_ON_EXPRESSION);
}
}