Function ExecInitRecursiveUnion

src/backend/executor/nodeRecursiveunion.c:179–283

---------------------------------------------------------------- * ExecInitRecursiveUnion * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
RecursiveUnionState *
ExecInitRecursiveUnion(RecursiveUnion *node, EState *estate, int eflags)
{
	RecursiveUnionState *rustate;
	ParamExecData *prmdata;

	/* check for unsupported flags */
	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

	/*
	 * create state structure
	 */
	rustate = makeNode(RecursiveUnionState);
	rustate->ps.plan = (Plan *) node;
	rustate->ps.state = estate;
	rustate->ps.ExecProcNode = ExecRecursiveUnion;

	rustate->eqfuncoids = NULL;
	rustate->hashfunctions = NULL;
	rustate->hashtable = NULL;
	rustate->tempContext = NULL;
	rustate->tableContext = NULL;

	/* initialize processing state */
	rustate->recursing = false;
	rustate->intermediate_empty = true;
	rustate->working_table = tuplestore_begin_heap(false, false, work_mem);
	rustate->intermediate_table = tuplestore_begin_heap(false, false, work_mem);
	rustate->refcount = 0;

	/*
	 * If hashing, we need a per-tuple memory context for comparisons, and a
	 * longer-lived context to store the hash table.  The table can't just be
	 * kept in the per-query context because we want to be able to throw it
	 * away when rescanning.
	 *
	 * RECURSIVE_CTE_FIXME: It suppose plan->numCols should be 0 if we don't
	 * support recursive union. QP should fix this later.
	 */
	if (node->numCols > 0)
	{
		rustate->tempContext =
			AllocSetContextCreate(CurrentMemoryContext,
								  "RecursiveUnion",
								  ALLOCSET_DEFAULT_SIZES);
		rustate->tableContext =
			AllocSetContextCreate(CurrentMemoryContext,
								  "RecursiveUnion hash table",
								  ALLOCSET_DEFAULT_SIZES);
	}

	/*
	 * Make the state structure available to descendant WorkTableScan nodes
	 * via the Param slot reserved for it.
	 */
	prmdata = &(estate->es_param_exec_vals[node->wtParam]);
	Assert(prmdata->execPlan == NULL);
	prmdata->value = PointerGetDatum(rustate);