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110 lines
2.7 KiB
C++
110 lines
2.7 KiB
C++
#include <Parsers/ParserCase.h>
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#include <Parsers/ExpressionElementParsers.h>
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#include <Parsers/ExpressionListParsers.h>
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#include <Parsers/ASTFunction.h>
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#include <Parsers/ASTLiteral.h>
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#include <Core/Field.h>
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namespace DB
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{
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bool ParserCase::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
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{
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ParserKeyword s_case{"CASE"};
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ParserKeyword s_when{"WHEN"};
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ParserKeyword s_then{"THEN"};
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ParserKeyword s_else{"ELSE"};
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ParserKeyword s_end{ "END"};
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ParserExpressionWithOptionalAlias p_expr{false};
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if (!s_case.ignore(pos, expected))
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return false;
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auto old_pos = pos;
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bool has_case_expr = !s_when.ignore(pos, expected);
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pos = old_pos;
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ASTs args;
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auto parse_branches = [&]()
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{
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bool has_branch = false;
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while (s_when.ignore(pos, expected))
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{
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has_branch = true;
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ASTPtr expr_when;
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if (!p_expr.parse(pos, expr_when, expected))
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return false;
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args.push_back(expr_when);
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if (!s_then.ignore(pos, expected))
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return false;
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ASTPtr expr_then;
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if (!p_expr.parse(pos, expr_then, expected))
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return false;
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args.push_back(expr_then);
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}
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if (!has_branch)
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return false;
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ASTPtr expr_else;
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if (s_else.ignore(pos, expected))
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{
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if (!p_expr.parse(pos, expr_else, expected))
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return false;
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}
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else
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{
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Field field_with_null;
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ASTLiteral null_literal(field_with_null);
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expr_else = std::make_shared<ASTLiteral>(null_literal);
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}
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args.push_back(expr_else);
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return s_end.ignore(pos, expected);
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};
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if (has_case_expr)
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{
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ASTPtr case_expr;
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if (!p_expr.parse(pos, case_expr, expected))
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return false;
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args.push_back(case_expr);
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if (!parse_branches())
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return false;
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auto function_args = std::make_shared<ASTExpressionList>();
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function_args->children = std::move(args);
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auto function = std::make_shared<ASTFunction>();
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function->name = "caseWithExpression";
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function->arguments = function_args;
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function->children.push_back(function->arguments);
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node = function;
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}
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else
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{
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if (!parse_branches())
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return false;
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auto function_args = std::make_shared<ASTExpressionList>();
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function_args->children = std::move(args);
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auto function = std::make_shared<ASTFunction>();
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function->name = "multiIf";
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function->arguments = function_args;
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function->children.push_back(function->arguments);
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node = function;
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}
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return true;
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}
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}
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