opToPartList, topOps, topSelOps, opParseCtx, joinContext, topToTable,
loadTableWork, loadFileWork, ctx, idToTableNameMap, destTableId, uCtx,
listMapJoinOpsNoReducer, groupOpToInputTables, prunedPartitions,
opToSamplePruner, globalLimitCtx, nameToSplitSample, inputs, rootTasks);
Optimizer optm = new Optimizer();
optm.setPctx(pCtx);
optm.initialize(conf);
pCtx = optm.optimize();
init(pCtx);
qb = pCtx.getQB();
// At this point we have the complete operator tree
// from which we want to find the reduce operator