Minor cleanups in the BRIN code

BRIN bloom and minmax-multi opclasses were somewhat inconsistent when
dealing with bool variables, assigning to them Datum values etc. While
not a bug, it makes the code harder to understand, so fix that.

While at it, update an incorrect comment copied to bloom opclass from
minmax, talking about strategies not supported by bloom.

Reviewed-by: Heikki Linnakangas
Discussion: https://postgr.es/m/0e1f3350-c9cf-ab62-43a5-5dae314de89c%40enterprisedb.com

src/backend/access/brin/brin_bloom.c

@@ -574,7 +574,7 @@ brin_bloom_consistent(PG_FUNCTION_ARGS)
 	Oid			colloid = PG_GET_COLLATION();
 	AttrNumber	attno;
 	Datum		value;
-	Datum		matches;
+	bool		matches;
 	FmgrInfo   *finfo;
 	uint32		hashValue;
 	BloomFilter *filter;
@@ -584,6 +584,10 @@ brin_bloom_consistent(PG_FUNCTION_ARGS)
 
 	Assert(filter);
 
+	/*
+	 * Assume all scan keys match. We'll be searching for a scan key eliminating
+	 * the page range (we can stop on the first such key).
+	 */
 	matches = true;
 
 	for (keyno = 0; keyno < nkeys; keyno++)
@@ -601,9 +605,8 @@ brin_bloom_consistent(PG_FUNCTION_ARGS)
 			case BloomEqualStrategyNumber:
 
 				/*
-				 * In the equality case (WHERE col = someval), we want to
-				 * return the current page range if the minimum value in the
-				 * range <= scan key, and the maximum value >= scan key.
+				 * We want to return the current page range if the bloom filter
+				 * seems to contain the value.
 				 */
 				finfo = bloom_get_procinfo(bdesc, attno, PROCNUM_HASH);
 
@@ -614,7 +617,7 @@ brin_bloom_consistent(PG_FUNCTION_ARGS)
 			default:
 				/* shouldn't happen */
 				elog(ERROR, "invalid strategy number %d", key->sk_strategy);
-				matches = 0;
+				matches = false;
 				break;
 		}
 
@@ -622,7 +625,7 @@ brin_bloom_consistent(PG_FUNCTION_ARGS)
 			break;
 	}
 
-	PG_RETURN_DATUM(matches);
+	PG_RETURN_BOOL(matches);
 }
 
 /*

src/backend/access/brin/brin_minmax_multi.c

@@ -2602,7 +2602,7 @@ brin_minmax_multi_consistent(PG_FUNCTION_ARGS)
 
 		for (keyno = 0; keyno < nkeys; keyno++)
 		{
-			Datum		matches;
+			bool		matches;
 			ScanKey		key = keys[keyno];
 
 			/* NULL keys are handled and filtered-out in bringetbitmap */
@@ -2618,7 +2618,7 @@ brin_minmax_multi_consistent(PG_FUNCTION_ARGS)
 					finfo = minmax_multi_get_strategy_procinfo(bdesc, attno, subtype,
 															   key->sk_strategy);
 					/* first value from the array */
-					matches = FunctionCall2Coll(finfo, colloid, minval, value);
+					matches = DatumGetBool(FunctionCall2Coll(finfo, colloid, minval, value));
 					break;
 
 				case BTEqualStrategyNumber:
@@ -2664,18 +2664,18 @@ brin_minmax_multi_consistent(PG_FUNCTION_ARGS)
 					finfo = minmax_multi_get_strategy_procinfo(bdesc, attno, subtype,
 															   key->sk_strategy);
 					/* last value from the array */
-					matches = FunctionCall2Coll(finfo, colloid, maxval, value);
+					matches = DatumGetBool(FunctionCall2Coll(finfo, colloid, maxval, value));
 					break;
 
 				default:
 					/* shouldn't happen */
 					elog(ERROR, "invalid strategy number %d", key->sk_strategy);
-					matches = 0;
+					matches = false;
 					break;
 			}
 
 			/* the range has to match all the scan keys */
-			matching &= DatumGetBool(matches);
+			matching &= matches;
 
 			/* once we find a non-matching key, we're done */
 			if (!matching)
@@ -2686,7 +2686,7 @@ brin_minmax_multi_consistent(PG_FUNCTION_ARGS)
 		 * have we found a range matching all scan keys? if yes, we're done
 		 */
 		if (matching)
-			PG_RETURN_DATUM(BoolGetDatum(true));
+			PG_RETURN_BOOL(true);
 	}
 
 	/*
@@ -2703,7 +2703,7 @@ brin_minmax_multi_consistent(PG_FUNCTION_ARGS)
 
 		for (keyno = 0; keyno < nkeys; keyno++)
 		{
-			Datum		matches;
+			bool		matches;
 			ScanKey		key = keys[keyno];
 
 			/* we've already dealt with NULL keys at the beginning */
@@ -2723,18 +2723,18 @@ brin_minmax_multi_consistent(PG_FUNCTION_ARGS)
 
 					finfo = minmax_multi_get_strategy_procinfo(bdesc, attno, subtype,
 															   key->sk_strategy);
-					matches = FunctionCall2Coll(finfo, colloid, val, value);
+					matches = DatumGetBool(FunctionCall2Coll(finfo, colloid, val, value));
 					break;
 
 				default:
 					/* shouldn't happen */
 					elog(ERROR, "invalid strategy number %d", key->sk_strategy);
-					matches = 0;
+					matches = false;
 					break;
 			}
 
 			/* the range has to match all the scan keys */
-			matching &= DatumGetBool(matches);
+			matching &= matches;
 
 			/* once we find a non-matching key, we're done */
 			if (!matching)
@@ -2743,10 +2743,10 @@ brin_minmax_multi_consistent(PG_FUNCTION_ARGS)
 
 		/* have we found a range matching all scan keys? if yes, we're done */
 		if (matching)
-			PG_RETURN_DATUM(BoolGetDatum(true));
+			PG_RETURN_BOOL(true);
 	}
 
-	PG_RETURN_DATUM(BoolGetDatum(false));
+	PG_RETURN_BOOL(false);
 }
 
 /*