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590 -> 537
92 lines
2.8 KiB
C++
92 lines
2.8 KiB
C++
#include <Common/typeid_cast.h>
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#include <Parsers/ASTFunction.h>
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#include <Parsers/ASTExpressionList.h>
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#include <Interpreters/OptimizeIfChains.h>
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#include <IO/WriteHelpers.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 NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
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extern const int UNEXPECTED_AST_STRUCTURE;
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}
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void OptimizeIfChainsVisitor::visit(ASTPtr & current_ast)
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{
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if (!current_ast)
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return;
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for (ASTPtr & child : current_ast->children)
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{
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/// Fallthrough cases
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const auto * function_node = child->as<ASTFunction>();
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if (!function_node || function_node->name != "if" || !function_node->arguments)
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{
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visit(child);
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continue;
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}
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const auto * function_args = function_node->arguments->as<ASTExpressionList>();
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if (!function_args || function_args->children.size() != 3 || !function_args->children[2])
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{
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visit(child);
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continue;
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}
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const auto * else_arg = function_args->children[2]->as<ASTFunction>();
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if (!else_arg || else_arg->name != "if")
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{
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visit(child);
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continue;
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}
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/// The case of:
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/// if(cond, a, if(...))
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auto chain = ifChain(child);
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std::reverse(chain.begin(), chain.end());
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child->as<ASTFunction>()->name = "multiIf";
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child->as<ASTFunction>()->arguments->children = std::move(chain);
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}
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}
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ASTs OptimizeIfChainsVisitor::ifChain(const ASTPtr & child)
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{
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const auto * function_node = child->as<ASTFunction>();
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if (!function_node || !function_node->arguments)
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throw Exception("Unexpected AST for function 'if'", ErrorCodes::UNEXPECTED_AST_STRUCTURE);
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const auto * function_args = function_node->arguments->as<ASTExpressionList>();
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if (!function_args || function_args->children.size() != 3)
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throw Exception("Wrong number of arguments for function 'if' (" + toString(function_args->children.size()) + " instead of 3)",
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ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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const auto * else_arg = function_args->children[2]->as<ASTFunction>();
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/// Recursively collect arguments from the innermost if ("head-recursion").
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/// Arguments will be returned in reverse order.
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if (else_arg && else_arg->name == "if")
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{
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auto cur = ifChain(function_node->arguments->children[2]);
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cur.push_back(function_node->arguments->children[1]);
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cur.push_back(function_node->arguments->children[0]);
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return cur;
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}
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else
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{
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ASTs end;
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end.reserve(3);
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end.push_back(function_node->arguments->children[2]);
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end.push_back(function_node->arguments->children[1]);
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end.push_back(function_node->arguments->children[0]);
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return end;
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}
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}
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}
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