Function CheckForAssertViolations

src/backend/executor/nodeAssertOp.c:27–64

* Check for assert violations and error out, if any. */

 * Check for assert violations and error out, if any.
 */
static void
CheckForAssertViolations(AssertOpState* node, TupleTableSlot* slot)
{
	AssertOp* plannode = (AssertOp*) node->ps.plan;
	ExprContext* econtext = node->ps.ps_ExprContext;
	ResetExprContext(econtext);
	/* Arrange for econtext's scan tuple to be the tuple under test */
	econtext->ecxt_outertuple = slot;
	/*
	 * Run in short-lived per-tuple context while computing expressions.
	 */
	MemoryContext oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
	StringInfoData errorString;
	initStringInfo(&errorString);

	ExprState *clause = node->ps.qual;
	bool isNull = false;
	Datum expr_value = ExecEvalExpr(clause, econtext, &isNull);

	if (!isNull && !DatumGetBool(expr_value))
	{
		Value *valErrorMessage = (Value*) list_nth(plannode->errmessage, 0);

		Assert(NULL != valErrorMessage && IsA(valErrorMessage, String) &&
				0 < strlen(strVal(valErrorMessage)));

		appendStringInfo(&errorString, "%s\n", strVal(valErrorMessage));

		ereport(ERROR,
				(errcode(plannode->errcode),
				 errmsg("one or more assertions failed"),
				 errdetail("%s", errorString.data)));
	}

	pfree(errorString.data);
	MemoryContextSwitchTo(oldContext);
	ResetExprContext(econtext);
}

/*
 * Evaluate Constraints (in node->ps.qual) and project output TupleTableSlot.