Remove mergeHyperLogLog.

It's buggy.  If somebody needs this later, they'll need to put back
a non-buggy vesion of it.

Discussion: CAM3SWZT-i6R9JU5YXa8MJUou2_r3LfGJZpQ9tYa1BYxfkj0=cQ@mail.gmail.com
Discussion: CAM3SWZRUOLsYoTT83QgdUy9D8ehYWm_nvbrrfcOOzikiRfFY7g@mail.gmail.com

Peter Geoghegan

src/backend/lib/hyperloglog.c

@@ -220,28 +220,6 @@ estimateHyperLogLog(hyperLogLogState *cState)
 	return result;
 }
 
-/*
- * Merges the estimate from one HyperLogLog state to another, returning the
- * estimate of their union.
- *
- * The number of registers in each must match.
- */
-void
-mergeHyperLogLog(hyperLogLogState *cState, const hyperLogLogState *oState)
-{
-	int			r;
-
-	if (cState->nRegisters != oState->nRegisters)
-		elog(ERROR, "number of registers mismatch: %zu != %zu",
-			 cState->nRegisters, oState->nRegisters);
-
-	for (r = 0; r < cState->nRegisters; ++r)
-	{
-		cState->hashesArr[r] = Max(cState->hashesArr[r], oState->hashesArr[r]);
-	}
-}
-
-
 /*
  * Worker for addHyperLogLog().
  *

src/include/lib/hyperloglog.h

@@ -63,7 +63,6 @@ extern void initHyperLogLog(hyperLogLogState *cState, uint8 bwidth);
 extern void initHyperLogLogError(hyperLogLogState *cState, double error);
 extern void addHyperLogLog(hyperLogLogState *cState, uint32 hash);
 extern double estimateHyperLogLog(hyperLogLogState *cState);
-extern void mergeHyperLogLog(hyperLogLogState *cState, const hyperLogLogState *oState);
 extern void freeHyperLogLog(hyperLogLogState *cState);
 
 #endif   /* HYPERLOGLOG_H */