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#pragma once
#include <Functions/JSONPath/Generator/IGenerator.h>
#include <Functions/JSONPath/Generator/VisitorJSONPathMemberAccess.h>
#include <Functions/JSONPath/Generator/VisitorJSONPathRange.h>
#include <Functions/JSONPath/Generator/VisitorJSONPathRoot.h>
#include <Functions/JSONPath/Generator/VisitorJSONPathStar.h>
#include <Functions/JSONPath/Generator/VisitorStatus.h>
#include <Functions/JSONPath/ASTs/ASTJSONPath.h>
namespace DB
{
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
}
template <typename JSONParser>
class GeneratorJSONPath : public IGenerator<JSONParser>
{
public:
/**
* Traverses children ASTs of ASTJSONPathQuery and creates a vector of corresponding visitors
* @param query_ptr_ pointer to ASTJSONPathQuery
*/
explicit GeneratorJSONPath(ASTPtr query_ptr_)
{
query_ptr = query_ptr_;
const auto * path = query_ptr->as<ASTJSONPath>();
if (!path)
{
throw Exception(ErrorCodes::LOGICAL_ERROR, "Invalid path");
}
const auto * query = path->jsonpath_query;
for (auto child_ast : query->children)
{
if (typeid_cast<ASTJSONPathRoot *>(child_ast.get()))
{
visitors.push_back(std::make_shared<VisitorJSONPathRoot<JSONParser>>(child_ast));
}
else if (typeid_cast<ASTJSONPathMemberAccess *>(child_ast.get()))
{
visitors.push_back(std::make_shared<VisitorJSONPathMemberAccess<JSONParser>>(child_ast));
}
else if (typeid_cast<ASTJSONPathRange *>(child_ast.get()))
{
visitors.push_back(std::make_shared<VisitorJSONPathRange<JSONParser>>(child_ast));
}
else if (typeid_cast<ASTJSONPathStar *>(child_ast.get()))
{
visitors.push_back(std::make_shared<VisitorJSONPathStar<JSONParser>>(child_ast));
}
}
}
const char * getName() const override { return "GeneratorJSONPath"; }
/**
* This method exposes API of traversing all paths, described by JSONPath,
* to SQLJSON Functions.
* Expected usage is to iteratively call this method from inside the function
* and to execute custom logic with received element or handle an error.
* On each such call getNextItem will yield next item into element argument
* and modify its internal state to prepare for next call.
*
* @param element root of JSON document
* @return is the generator exhausted
*/
VisitorStatus getNextItem(typename JSONParser::Element & element) override
{
while (true)
{
/// element passed to us actually is root, so here we assign current to root
auto current = element;
if (current_visitor < 0)
{
return VisitorStatus::Exhausted;
}
for (int i = 0; i < current_visitor; ++i)
{
visitors[i]->apply(current);
}
VisitorStatus status = VisitorStatus::Error;
for (size_t i = current_visitor; i < visitors.size(); ++i)
{
status = visitors[i]->visit(current);
current_visitor = static_cast<int>(i);
if (status == VisitorStatus::Error || status == VisitorStatus::Ignore)
{
break;
}
}
updateVisitorsForNextRun();
if (status != VisitorStatus::Ignore)
{
element = current;
return status;
}
}
}
private:
bool updateVisitorsForNextRun()
{
while (current_visitor >= 0 && visitors[current_visitor]->isExhausted())
{
visitors[current_visitor]->reinitialize();
current_visitor--;
}
if (current_visitor >= 0)
{
visitors[current_visitor]->updateState();
}
return current_visitor >= 0;
}
int current_visitor = 0;
ASTPtr query_ptr;
VisitorList<JSONParser> visitors;
};
}
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