OmniSciDB  cde582ebc3
 All Classes Namespaces Files Functions Variables Typedefs Enumerations Enumerator Friends Macros Groups Pages
SpeculativeTopN.h File Reference

Speculative top N algorithm. More...

#include <cstddef>
#include <cstdint>
#include <memory>
#include <mutex>
#include <stdexcept>
#include <unordered_map>
#include <vector>
+ Include dependency graph for SpeculativeTopN.h:
+ This graph shows which files directly or indirectly include this file:

Go to the source code of this file.


struct  SpeculativeTopNVal
struct  SpeculativeTopNEntry
class  SpeculativeTopNMap
class  SpeculativeTopNFailed
class  SpeculativeTopNBlacklist




bool use_speculative_top_n (const RelAlgExecutionUnit &, const QueryMemoryDescriptor &)

Detailed Description

Speculative top N algorithm.

Definition in file SpeculativeTopN.h.

Function Documentation

bool use_speculative_top_n ( const RelAlgExecutionUnit ra_exe_unit,
const QueryMemoryDescriptor query_mem_desc 

SpeculativeTopN sort is used when there are multiple already sorted results (when GPU sort is used on multiple devices, refer to GroupByAndAggregate::gpuCanHandleOrderEntries), and we want to pick top n elements (LIMIT caluse exists), and we have already chosen this algorithm when creating the proper work unit (refer to RelAlgExecutor::createSortInputWorkUnit).

Besides, we currently only support cases with 2 target expressions and only with COUNT aggregate (similar limitations exists in whether or not we support GPU sort).

Definition at line 189 of file SpeculativeTopN.cpp.

References SortInfo::algorithm, g_cluster, kCOUNT, SortInfo::limit, RelAlgExecutionUnit::sort_info, QueryMemoryDescriptor::sortOnGpu(), SpeculativeTopN, and RelAlgExecutionUnit::target_exprs.

Referenced by Executor::collectAllDeviceResults(), RelAlgExecutor::executeSort(), RelAlgExecutor::executeWorkUnit(), and QueryExecutionContext::launchGpuCode().

190  {
191  if (g_cluster) {
192  return false;
193  }
194  if (ra_exe_unit.target_exprs.size() != 2) {
195  return false;
196  }
197  for (const auto target_expr : ra_exe_unit.target_exprs) {
198  const auto agg_expr = dynamic_cast<const Analyzer::AggExpr*>(target_expr);
199  if (agg_expr && agg_expr->get_aggtype() != kCOUNT) {
200  return false;
201  }
202  }
203  return query_mem_desc.sortOnGpu() && ra_exe_unit.sort_info.limit &&
205 }
std::vector< Analyzer::Expr * > target_exprs
const SortAlgorithm algorithm
const size_t limit
Definition: sqldefs.h:77
bool g_cluster

+ Here is the call graph for this function:

+ Here is the caller graph for this function: