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https://github.com/ClickHouse/ClickHouse.git
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239 lines
7.3 KiB
C++
239 lines
7.3 KiB
C++
#include <Common/typeid_cast.h>
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#include <Columns/ColumnConst.h>
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#include <DataTypes/DataTypesNumber.h>
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#include <Parsers/IAST.h>
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#include <Parsers/ASTFunction.h>
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#include <Parsers/ASTIdentifier.h>
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#include <Parsers/ASTLiteral.h>
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#include <Parsers/ASTSelectQuery.h>
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#include <Parsers/ASTExpressionList.h>
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#include <Interpreters/TreeRewriter.h>
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#include <Interpreters/InDepthNodeVisitor.h>
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#include <IO/WriteBufferFromString.h>
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#include <Storages/transformQueryForExternalDatabase.h>
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#include <Storages/MergeTree/KeyCondition.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int LOGICAL_ERROR;
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}
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namespace
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{
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/// Everything except numbers is put as string literal.
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class ReplacingConstantExpressionsMatcherNumOrStr
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{
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public:
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using Data = Block;
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static bool needChildVisit(ASTPtr &, const ASTPtr &)
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{
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return true;
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}
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static void visit(ASTPtr & node, Block & block_with_constants)
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{
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if (!node->as<ASTFunction>())
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return;
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std::string name = node->getColumnName();
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if (block_with_constants.has(name))
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{
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auto result = block_with_constants.getByName(name);
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if (!isColumnConst(*result.column))
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return;
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if (result.column->isNullAt(0))
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{
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node = std::make_shared<ASTLiteral>(Field());
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}
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else if (isNumber(result.type))
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{
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node = std::make_shared<ASTLiteral>(assert_cast<const ColumnConst &>(*result.column).getField());
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}
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else
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{
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/// Everything except numbers is put as string literal. This is important for Date, DateTime, UUID.
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const IColumn & inner_column = assert_cast<const ColumnConst &>(*result.column).getDataColumn();
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WriteBufferFromOwnString out;
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result.type->serializeAsText(inner_column, 0, out, FormatSettings());
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node = std::make_shared<ASTLiteral>(out.str());
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}
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}
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}
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};
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class DropAliasesMatcher
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{
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public:
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struct Data {};
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Data data;
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static bool needChildVisit(ASTPtr &, const ASTPtr &)
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{
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return true;
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}
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static void visit(ASTPtr & node, Data)
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{
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if (!node->tryGetAlias().empty())
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node->setAlias({});
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}
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};
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void replaceConstantExpressions(ASTPtr & node, const Context & context, const NamesAndTypesList & all_columns)
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{
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auto syntax_result = TreeRewriter(context).analyze(node, all_columns);
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Block block_with_constants = KeyCondition::getBlockWithConstants(node, syntax_result, context);
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InDepthNodeVisitor<ReplacingConstantExpressionsMatcherNumOrStr, true> visitor(block_with_constants);
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visitor.visit(node);
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}
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void dropAliases(ASTPtr & node)
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{
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DropAliasesMatcher::Data data;
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InDepthNodeVisitor<DropAliasesMatcher, true> visitor(data);
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visitor.visit(node);
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}
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bool isCompatible(const IAST & node)
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{
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if (const auto * function = node.as<ASTFunction>())
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{
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if (function->parameters) /// Parametric aggregate functions
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return false;
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if (!function->arguments)
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throw Exception("Logical error: function->arguments is not set", ErrorCodes::LOGICAL_ERROR);
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String name = function->name;
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if (!(name == "and"
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|| name == "or"
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|| name == "not"
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|| name == "equals"
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|| name == "notEquals"
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|| name == "less"
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|| name == "greater"
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|| name == "lessOrEquals"
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|| name == "greaterOrEquals"
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|| name == "like"
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|| name == "notLike"
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|| name == "in"
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|| name == "notIn"
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|| name == "tuple"))
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return false;
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/// A tuple with zero or one elements is represented by a function tuple(x) and is not compatible,
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/// but a normal tuple with more than one element is represented as a parenthesized expression (x, y) and is perfectly compatible.
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if (name == "tuple" && function->arguments->children.size() <= 1)
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return false;
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/// If the right hand side of IN is an identifier (example: x IN table), then it's not compatible.
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if ((name == "in" || name == "notIn")
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&& (function->arguments->children.size() != 2
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|| function->arguments->children[1]->as<ASTIdentifier>()))
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return false;
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for (const auto & expr : function->arguments->children)
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if (!isCompatible(*expr))
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return false;
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return true;
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}
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if (const auto * literal = node.as<ASTLiteral>())
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{
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/// Foreign databases often have no support for Array. But Tuple literals are passed to support IN clause.
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return literal->value.getType() != Field::Types::Array;
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}
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return node.as<ASTIdentifier>();
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}
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}
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String transformQueryForExternalDatabase(
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const SelectQueryInfo & query_info,
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const NamesAndTypesList & available_columns,
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IdentifierQuotingStyle identifier_quoting_style,
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const String & database,
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const String & table,
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const Context & context)
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{
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auto clone_query = query_info.query->clone();
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const Names used_columns = query_info.syntax_analyzer_result->requiredSourceColumns();
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auto select = std::make_shared<ASTSelectQuery>();
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select->replaceDatabaseAndTable(database, table);
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auto select_expr_list = std::make_shared<ASTExpressionList>();
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for (const auto & name : used_columns)
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select_expr_list->children.push_back(std::make_shared<ASTIdentifier>(name));
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select->setExpression(ASTSelectQuery::Expression::SELECT, std::move(select_expr_list));
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/** If there was WHERE,
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* copy it to transformed query if it is compatible,
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* or if it is AND expression,
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* copy only compatible parts of it.
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*/
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ASTPtr original_where = clone_query->as<ASTSelectQuery &>().where();
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if (original_where)
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{
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replaceConstantExpressions(original_where, context, available_columns);
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if (isCompatible(*original_where))
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{
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select->setExpression(ASTSelectQuery::Expression::WHERE, std::move(original_where));
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}
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else if (const auto * function = original_where->as<ASTFunction>())
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{
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if (function->name == "and")
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{
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bool compatible_found = false;
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auto new_function_and = makeASTFunction("and");
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for (const auto & elem : function->arguments->children)
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{
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if (isCompatible(*elem))
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{
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new_function_and->arguments->children.push_back(elem);
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compatible_found = true;
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}
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}
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if (new_function_and->arguments->children.size() == 1)
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new_function_and->name = "";
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if (compatible_found)
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select->setExpression(ASTSelectQuery::Expression::WHERE, std::move(new_function_and));
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}
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}
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}
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ASTPtr select_ptr = select;
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dropAliases(select_ptr);
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WriteBufferFromOwnString out;
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IAST::FormatSettings settings(out, true);
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settings.identifier_quoting_style = identifier_quoting_style;
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settings.always_quote_identifiers = identifier_quoting_style != IdentifierQuotingStyle::None;
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select->format(settings);
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return out.str();
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}
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}
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