Function ExecInitQual

src/backend/executor/execExpr.c:220–295

* ExecInitQual: prepare a qual for execution by ExecQual * * Prepares for the evaluation of a conjunctive boolean expression (qual list * with implicit AND semantics) that returns true if none of the * subexpressions are false. * * We must return true if the list is empty. Since that's a very common case, * we optimize it a bit further by translating to a NULL ExprState pointer * rather t

 * get selected.
 */
ExprState *
ExecInitQual(List *qual, PlanState *parent)
{
	ExprState  *state;
	ExprEvalStep scratch = {0};
	List	   *adjust_jumps = NIL;
	ListCell   *lc;

	/* short-circuit (here and in ExecQual) for empty restriction list */
	if (qual == NIL)
		return NULL;

	Assert(IsA(qual, List));

	state = makeNode(ExprState);
	state->expr = (Expr *) qual;
	state->parent = parent;
	state->ext_params = NULL;

	/* mark expression as to be used with ExecQual() */
	state->flags = EEO_FLAG_IS_QUAL;

	/* Insert EEOP_*_FETCHSOME steps as needed */
	ExecInitExprSlots(state, (Node *) qual);

	/*
	 * ExecQual() needs to return false for an expression returning NULL. That
	 * allows us to short-circuit the evaluation the first time a NULL is
	 * encountered.  As qual evaluation is a hot-path this warrants using a
	 * special opcode for qual evaluation that's simpler than BOOL_AND (which
	 * has more complex NULL handling).
	 */
	scratch.opcode = EEOP_QUAL;

	/*
	 * We can use ExprState's resvalue/resnull as target for each qual expr.
	 */
	scratch.resvalue = &state->resvalue;
	scratch.resnull = &state->resnull;

	foreach(lc, qual)
	{
		Expr	   *node = (Expr *) lfirst(lc);

		/* first evaluate expression */
		ExecInitExprRec(node, state, &state->resvalue, &state->resnull);

		/* then emit EEOP_QUAL to detect if it's false (or null) */
		scratch.d.qualexpr.jumpdone = -1;
		ExprEvalPushStep(state, &scratch);
		adjust_jumps = lappend_int(adjust_jumps,
								   state->steps_len - 1);
	}

	/* adjust jump targets */
	foreach(lc, adjust_jumps)
	{
		ExprEvalStep *as = &state->steps[lfirst_int(lc)];