Method PrepareScalarExpression

be/src/benchmarks/expr-benchmark.cc:94–154

Create ExprTestData for a given query. Returned *test_data contains valid ExprTestData* in which eval_ is already opened. Assumes 'query' is a constant query.

  // Returned *test_data contains valid ExprTestData* in which eval_ is already opened.
  // Assumes 'query' is a constant query.
  Status PrepareScalarExpression(const string& query, ExprTestData** test_data) {
    TExecRequest request;
    TQueryCtx query_ctx;
    query_ctx.__set_session(session_state_);
    query_ctx.client_request.__set_stmt(query);
    query_ctx.client_request.__set_query_options(query_options_);
    string dummy_hostname = "";
    NetworkAddressPB dummy_addr;
    ImpalaServer::PrepareQueryContext(dummy_hostname, dummy_addr, &query_ctx);

    RuntimeState* state = pool_.Add(new RuntimeState(query_ctx, &exec_env_));
    TPlanFragment* fragment = state->obj_pool()->Add(new TPlanFragment());
    PlanFragmentCtxPB* fragment_ctx = state->obj_pool()->Add(new PlanFragmentCtxPB());

    FragmentState* fragment_state = state->obj_pool()->Add(
        new FragmentState(state->query_state(), *fragment, *fragment_ctx));
    RETURN_IF_ERROR(frontend_.GetExecRequest(query_ctx, &request));

    // For query "select 1 + 1", planner will return query plan:
    //
    // F00:PLAN FRAGMENT [UNPARTITIONED] hosts=1 instances=1
    // |  Per-Host Resources: mem-estimate=4.00MB mem-reservation=4.00MB thread-reservation=1
    // PLAN-ROOT SINK
    // |  output exprs: 1 + 1
    // |  mem-estimate=4.00MB mem-reservation=4.00MB spill-buffer=2.00MB thread-reservation=0
    // |
    // 00:UNION
    //    constant-operands=1
    //    mem-estimate=0B mem-reservation=0B thread-reservation=0
    //    tuple-ids=0 row-size=2B cardinality=1
    //
    // However, the TExpr for the scalar expression is not in the output_sink's
    // output_exprs. Instead, it is in the union node's const_expr_lists.
    const TQueryExecRequest& query_request = request.query_exec_request;
    TUnionNode union_node =
        query_request.plan_exec_info[0].fragments[0].plan.nodes[0].union_node;
    vector<TExpr> texprs = union_node.const_expr_lists[0];
    DCHECK_EQ(texprs.size(), 1);

    ScalarExpr* expr;
    RETURN_IF_ERROR(
        ScalarExpr::Create(texprs[0], RowDescriptor(), fragment_state, &expr));
    ScalarExprEvaluator* eval;
    RETURN_IF_ERROR(ScalarExprEvaluator::Create(
        *expr, state, state->obj_pool(), &expr_perm_pool_, &expr_results_pool_, &eval));

    // UDFs which cannot be interpreted need to be handled by codegen.
    // This follow examples from fe-support.cc
    if (fragment_state->ScalarExprNeedsCodegen()) {
      RETURN_IF_ERROR(fragment_state->CreateCodegen());
      LlvmCodeGen* codegen = fragment_state->codegen();
      DCHECK(codegen != NULL);
      RETURN_IF_ERROR(fragment_state->CodegenScalarExprs());
      codegen->EnableOptimizations(true);
      RETURN_IF_ERROR(codegen->FinalizeModule());
    }
    RETURN_IF_ERROR(eval->Open(state));