ClickHouse/src/Interpreters/evaluateConstantExpression.cpp
Ivan 1d170f5745
ASTTableIdentifier Part #1: improve internal representation of ASTIdentifier name (#16149)
* Use only |name_parts| as primary name source

* Restore legacy logic for table restoration

* Fix build

* Fix tests

* Add pytest server config

* Fix tests

* Fixes due to review
2020-10-24 21:46:10 +03:00

353 lines
11 KiB
C++

#include <Interpreters/evaluateConstantExpression.h>
#include <Columns/ColumnConst.h>
#include <Columns/ColumnsNumber.h>
#include <Core/Block.h>
#include <DataTypes/DataTypesNumber.h>
#include <Interpreters/Context.h>
#include <Interpreters/convertFieldToType.h>
#include <Interpreters/ExpressionActions.h>
#include <Interpreters/ExpressionAnalyzer.h>
#include <Interpreters/TreeRewriter.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ExpressionElementParsers.h>
#include <TableFunctions/TableFunctionFactory.h>
#include <Common/typeid_cast.h>
#include <Interpreters/ReplaceQueryParameterVisitor.h>
#include <Poco/Util/AbstractConfiguration.h>
namespace DB
{
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
extern const int BAD_ARGUMENTS;
}
std::pair<Field, std::shared_ptr<const IDataType>> evaluateConstantExpression(const ASTPtr & node, const Context & context)
{
NamesAndTypesList source_columns = {{ "_dummy", std::make_shared<DataTypeUInt8>() }};
auto ast = node->clone();
ReplaceQueryParameterVisitor param_visitor(context.getQueryParameters());
param_visitor.visit(ast);
String name = ast->getColumnName();
auto syntax_result = TreeRewriter(context).analyze(ast, source_columns);
ExpressionActionsPtr expr_for_constant_folding = ExpressionAnalyzer(ast, syntax_result, context).getConstActions();
/// There must be at least one column in the block so that it knows the number of rows.
Block block_with_constants{{ ColumnConst::create(ColumnUInt8::create(1, 0), 1), std::make_shared<DataTypeUInt8>(), "_dummy" }};
expr_for_constant_folding->execute(block_with_constants);
if (!block_with_constants || block_with_constants.rows() == 0)
throw Exception("Logical error: empty block after evaluation of constant expression for IN, VALUES or LIMIT", ErrorCodes::LOGICAL_ERROR);
if (!block_with_constants.has(name))
throw Exception("Element of set in IN, VALUES or LIMIT is not a constant expression (result column not found): " + name, ErrorCodes::BAD_ARGUMENTS);
const ColumnWithTypeAndName & result = block_with_constants.getByName(name);
const IColumn & result_column = *result.column;
/// Expressions like rand() or now() are not constant
if (!isColumnConst(result_column))
throw Exception("Element of set in IN, VALUES or LIMIT is not a constant expression (result column is not const): " + name, ErrorCodes::BAD_ARGUMENTS);
return std::make_pair(result_column[0], result.type);
}
ASTPtr evaluateConstantExpressionAsLiteral(const ASTPtr & node, const Context & context)
{
/// If it's already a literal.
if (node->as<ASTLiteral>())
return node;
return std::make_shared<ASTLiteral>(evaluateConstantExpression(node, context).first);
}
ASTPtr evaluateConstantExpressionOrIdentifierAsLiteral(const ASTPtr & node, const Context & context)
{
if (const auto * id = node->as<ASTIdentifier>())
return std::make_shared<ASTLiteral>(id->name());
return evaluateConstantExpressionAsLiteral(node, context);
}
ASTPtr evaluateConstantExpressionForDatabaseName(const ASTPtr & node, const Context & context)
{
ASTPtr res = evaluateConstantExpressionOrIdentifierAsLiteral(node, context);
auto & literal = res->as<ASTLiteral &>();
if (literal.value.safeGet<String>().empty())
{
String current_database = context.getCurrentDatabase();
if (current_database.empty())
{
/// Table was created on older version of ClickHouse and CREATE contains not folded expression.
/// Current database is not set yet during server startup, so we cannot evaluate it correctly.
literal.value = context.getConfigRef().getString("default_database", "default");
}
else
literal.value = current_database;
}
return res;
}
namespace
{
using Conjunction = ColumnsWithTypeAndName;
using Disjunction = std::vector<Conjunction>;
Disjunction analyzeEquals(const ASTIdentifier * identifier, const Field & value, const ExpressionActionsPtr & expr)
{
if (!identifier || value.isNull())
{
return {};
}
for (const auto & name_and_type : expr->getRequiredColumnsWithTypes())
{
const auto & name = name_and_type.name;
const auto & type = name_and_type.type;
if (name == identifier->name())
{
ColumnWithTypeAndName column;
Field converted = convertFieldToType(value, *type);
if (converted.isNull())
return {};
column.column = type->createColumnConst(1, converted);
column.name = name;
column.type = type;
return {{std::move(column)}};
}
}
return {};
}
Disjunction analyzeEquals(const ASTIdentifier * identifier, const ASTLiteral * literal, const ExpressionActionsPtr & expr)
{
if (!identifier || !literal)
{
return {};
}
return analyzeEquals(identifier, literal->value, expr);
}
Disjunction andDNF(const Disjunction & left, const Disjunction & right)
{
if (left.empty())
{
return right;
}
Disjunction result;
for (const auto & conjunct1 : left)
{
for (const auto & conjunct2 : right)
{
Conjunction new_conjunct{conjunct1};
new_conjunct.insert(new_conjunct.end(), conjunct2.begin(), conjunct2.end());
result.emplace_back(new_conjunct);
}
}
return result;
}
Disjunction analyzeFunction(const ASTFunction * fn, const ExpressionActionsPtr & expr)
{
if (!fn)
{
return {};
}
// TODO: enumerate all possible function names!
if (fn->name == "equals")
{
const auto * left = fn->arguments->children.front().get();
const auto * right = fn->arguments->children.back().get();
const auto * identifier = left->as<ASTIdentifier>() ? left->as<ASTIdentifier>() : right->as<ASTIdentifier>();
const auto * literal = left->as<ASTLiteral>() ? left->as<ASTLiteral>() : right->as<ASTLiteral>();
return analyzeEquals(identifier, literal, expr);
}
else if (fn->name == "in")
{
const auto * left = fn->arguments->children.front().get();
const auto * right = fn->arguments->children.back().get();
const auto * identifier = left->as<ASTIdentifier>();
Disjunction result;
if (const auto * tuple_func = right->as<ASTFunction>(); tuple_func && tuple_func->name == "tuple")
{
const auto * tuple_elements = tuple_func->children.front()->as<ASTExpressionList>();
for (const auto & child : tuple_elements->children)
{
const auto * literal = child->as<ASTLiteral>();
const auto dnf = analyzeEquals(identifier, literal, expr);
if (dnf.empty())
{
return {};
}
result.insert(result.end(), dnf.begin(), dnf.end());
}
}
else if (const auto * tuple_literal = right->as<ASTLiteral>();
tuple_literal && tuple_literal->value.getType() == Field::Types::Tuple)
{
const auto & tuple = tuple_literal->value.get<const Tuple &>();
for (const auto & child : tuple)
{
const auto dnf = analyzeEquals(identifier, child, expr);
if (dnf.empty())
{
return {};
}
result.insert(result.end(), dnf.begin(), dnf.end());
}
}
else
{
return {};
}
return result;
}
else if (fn->name == "or")
{
const auto * args = fn->children.front()->as<ASTExpressionList>();
if (!args)
{
return {};
}
Disjunction result;
for (const auto & arg : args->children)
{
const auto dnf = analyzeFunction(arg->as<ASTFunction>(), expr);
if (dnf.empty())
{
return {};
}
result.insert(result.end(), dnf.begin(), dnf.end());
}
return result;
}
else if (fn->name == "and")
{
const auto * args = fn->children.front()->as<ASTExpressionList>();
if (!args)
{
return {};
}
Disjunction result;
for (const auto & arg : args->children)
{
const auto dnf = analyzeFunction(arg->as<ASTFunction>(), expr);
if (dnf.empty())
{
continue;
}
result = andDNF(result, dnf);
}
return result;
}
return {};
}
}
std::optional<Blocks> evaluateExpressionOverConstantCondition(const ASTPtr & node, const ExpressionActionsPtr & target_expr)
{
Blocks result;
// TODO: `node` may be always-false literal.
if (const auto * fn = node->as<ASTFunction>())
{
const auto dnf = analyzeFunction(fn, target_expr);
if (dnf.empty())
{
return {};
}
auto has_required_columns = [&target_expr](const Block & block) -> bool
{
for (const auto & name : target_expr->getRequiredColumns())
{
bool has_column = false;
for (const auto & column_name : block.getNames())
{
if (column_name == name)
{
has_column = true;
break;
}
}
if (!has_column)
return false;
}
return true;
};
for (const auto & conjunct : dnf)
{
Block block(conjunct);
// Block should contain all required columns from `target_expr`
if (!has_required_columns(block))
{
return {};
}
target_expr->execute(block);
if (block.rows() == 1)
{
result.push_back(block);
}
else if (block.rows() == 0)
{
// filter out cases like "WHERE a = 1 AND a = 2"
continue;
}
else
{
// FIXME: shouldn't happen
return {};
}
}
}
return {result};
}
}