in favor of unified proceedings pursuant to a federal statute that is at issue in the case. See Colo. River, 424 U.S. at 819-20, 96 S.Ct. 1236 (finding abstention appropriate because the federal law at issue evinced a clear policy against piecemeal adjudication of river system water rights); cf. Moses H. Cone, 460 U.S. at 20, 103 S.Ct. 927 (finding abstention inappropriate because the Federal Arbitration Act requires piecemeal litigation if necessary to give effect to an arbitration agreement). But there are other reasons why the piecemeal litigation factor might loom large in a given case. On multiple occasions, we have found an exceptional basis that counsels in favor of abstention, even though no particular federal policy was in play. See, e.g., Rivera-Feliciano, 438 F.3d at 50 (<HOLDING>); Currie, 290 F.3d at 10 (finding a risk of
holding that entry of judgment in the underlying litigation does not moot an appeal from a denial of a motion to intervene if one of the parties keeps the underlying litigation live by pursuing an appeal holding that in determining whether diversity jurisdiction exists in petition to compel arbitration district court was correct in looking only to citizenship of parties in action before it  parties who signed arbitration agreement  and that nondiverse agents in underlying state case were not indispensable parties as any potential prejudice resulting from piecemeal litigation is overcome by faas strong bias in favor of arbitration holding that in light of the many underlying unresolved issues of puerto rican law it would be better to avoid piecemeal litigation holding that statute would be applied retroactively when to do so would better effect the remedial intentions of the legislature in enacting it holding that district courts are required to compel arbitration of claims subject to arbitration clause even if the result is piecemeal litigation