mirror of
https://github.com/ClickHouse/ClickHouse.git
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142 lines
4.3 KiB
C++
142 lines
4.3 KiB
C++
#include <Core/NamesAndTypes.h>
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#include <Interpreters/Context.h>
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#include <Interpreters/SyntaxAnalyzer.h>
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#include <Interpreters/ExpressionAnalyzer.h>
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#include <Interpreters/ExpressionActions.h>
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#include <Interpreters/IdentifierSemantic.h>
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#include <Parsers/ASTIdentifier.h>
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#include <Parsers/ASTExpressionList.h>
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#include <Parsers/ASTLiteral.h>
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#include <Parsers/ASTFunction.h>
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#include <Parsers/ASTSelectQuery.h>
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#include <Columns/ColumnsNumber.h>
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#include <Columns/ColumnsCommon.h>
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#include <Storages/VirtualColumnUtils.h>
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#include <IO/WriteHelpers.h>
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#include <Common/typeid_cast.h>
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namespace DB
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{
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namespace
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{
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/// Verifying that the function depends only on the specified columns
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bool isValidFunction(const ASTPtr & expression, const NameSet & columns)
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{
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for (const auto & child : expression->children)
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if (!isValidFunction(child, columns))
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return false;
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if (auto opt_name = IdentifierSemantic::getColumnName(expression))
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return columns.count(*opt_name);
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return true;
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}
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/// Extract all subfunctions of the main conjunction, but depending only on the specified columns
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void extractFunctions(const ASTPtr & expression, const NameSet & columns, std::vector<ASTPtr> & result)
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{
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const auto * function = expression->as<ASTFunction>();
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if (function && function->name == "and")
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{
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for (const auto & child : function->arguments->children)
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extractFunctions(child, columns, result);
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}
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else if (isValidFunction(expression, columns))
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{
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result.push_back(expression->clone());
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}
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}
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/// Construct a conjunction from given functions
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ASTPtr buildWhereExpression(const ASTs & functions)
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{
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if (functions.empty())
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return nullptr;
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if (functions.size() == 1)
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return functions[0];
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return makeASTFunction("and", functions);
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}
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}
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namespace VirtualColumnUtils
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{
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void rewriteEntityInAst(ASTPtr ast, const String & column_name, const Field & value, const String & func)
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{
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auto & select = ast->as<ASTSelectQuery &>();
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if (!select.with())
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select.setExpression(ASTSelectQuery::Expression::WITH, std::make_shared<ASTExpressionList>());
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if (func.empty())
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{
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auto literal = std::make_shared<ASTLiteral>(value);
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literal->alias = column_name;
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literal->prefer_alias_to_column_name = true;
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select.with()->children.push_back(literal);
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}
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else
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{
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auto literal = std::make_shared<ASTLiteral>(value);
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literal->prefer_alias_to_column_name = true;
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auto function = makeASTFunction(func, literal);
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function->alias = column_name;
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function->prefer_alias_to_column_name = true;
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select.with()->children.push_back(function);
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}
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}
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void filterBlockWithQuery(const ASTPtr & query, Block & block, const Context & context)
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{
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const auto & select = query->as<ASTSelectQuery &>();
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if (!select.where() && !select.prewhere())
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return;
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NameSet columns;
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for (const auto & it : block.getNamesAndTypesList())
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columns.insert(it.name);
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/// We will create an expression that evaluates the expressions in WHERE and PREWHERE, depending only on the existing columns.
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std::vector<ASTPtr> functions;
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if (select.where())
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extractFunctions(select.where(), columns, functions);
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if (select.prewhere())
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extractFunctions(select.prewhere(), columns, functions);
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ASTPtr expression_ast = buildWhereExpression(functions);
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if (!expression_ast)
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return;
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/// Let's analyze and calculate the expression.
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auto syntax_result = SyntaxAnalyzer(context).analyze(expression_ast, block.getNamesAndTypesList());
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ExpressionAnalyzer analyzer(expression_ast, syntax_result, context);
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ExpressionActionsPtr actions = analyzer.getActions(false);
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Block block_with_filter = block;
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actions->execute(block_with_filter);
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/// Filter the block.
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String filter_column_name = expression_ast->getColumnName();
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ColumnPtr filter_column = block_with_filter.getByName(filter_column_name).column->convertToFullColumnIfConst();
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const IColumn::Filter & filter = typeid_cast<const ColumnUInt8 &>(*filter_column).getData();
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for (size_t i = 0; i < block.columns(); ++i)
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{
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ColumnPtr & column = block.safeGetByPosition(i).column;
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column = column->filter(filter, -1);
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}
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}
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}
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}
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