Support the old signature of BRIN consistent function

Commit a1c649d changed the signature of the BRIN consistent function
by adding a new required parameter.  Treating the parameter as optional,
which would make the change backwards incompatibile, was rejected with
the justification that there are few out-of-core extensions, so it's not
worth adding making the code more complex, and it's better to deal with
that in the extension.

But after further thought, that would be rather problematic, because
pg_upgrade simply dumps catalog contents and the same version of an
extension needs to work on both PostgreSQL versions. Supporting both
variants of the consistent function (with 3 or 4 arguments) makes that
possible.

The signature is not the only thing that changed, as commit 72ccf55
moved handling of IS [NOT] NULL keys from the support procedures. But
this change is backward compatible - handling the keys in exension is
unnecessary, but harmless. The consistent function will do a bit of
unnecessary work, but it should be very cheap.

This also undoes most of the changes to the existing opclasses (minmax
and inclusion), making them use the old signature again. This should
make backpatching simpler.

Catversion bump, because of changes in pg_amproc.

Author: Tomas Vondra <tomas.vondra@postgresql.org>
Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Reviewed-by: Mark Dilger <hornschnorter@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Masahiko Sawada <masahiko.sawada@enterprisedb.com>
Reviewed-by: John Naylor <john.naylor@enterprisedb.com>
Discussion: https://postgr.es/m/c1138ead-7668-f0e1-0638-c3be3237e812@2ndquadrant.com

Author: tvondra

doc/src/sgml/brin.sgml

@@ -476,6 +476,19 @@ typedef struct BrinOpcInfo
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><function>bool consistent(BrinDesc *bdesc, BrinValues *column,
+       ScanKey key)</function></term>
+    <listitem>
+     <para>
+      Returns whether the ScanKey is consistent with the given indexed
+      values for a range.
+      The attribute number to use is passed as part of the scan key.
+      This is an older backward-compatible variant of the consistent function.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><function>bool addValue(BrinDesc *bdesc, BrinValues *column,
        Datum newval, bool isnull)</function></term>

src/backend/access/brin/brin.c

@@ -634,26 +634,58 @@ bringetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
 						break;
 					}
 
+					/*
+					 * Collation from the first key (has to be the same for
+					 * all keys for the same attribue).
+					 */
+					collation = keys[attno - 1][0]->sk_collation;
+
 					/*
 					 * Check whether the scan key is consistent with the page
 					 * range values; if so, have the pages in the range added
 					 * to the output bitmap.
 					 *
-					 * XXX We simply use the collation from the first key (it
-					 * has to be the same for all keys for the same attribue).
+					 * The opclass may or may not support processing of multiple
+					 * scan keys. We can determine that based on the number of
+					 * arguments - functions with extra parameter (number of scan
+					 * keys) do support this, otherwise we have to simply pass the
+					 * scan keys one by one.
 					 */
-					collation = keys[attno - 1][0]->sk_collation;
-
-					/* Check all keys at once */
-					add = FunctionCall4Coll(&consistentFn[attno - 1],
-											collation,
-											PointerGetDatum(bdesc),
-											PointerGetDatum(bval),
-											PointerGetDatum(keys[attno - 1]),
-											Int32GetDatum(nkeys[attno - 1]));
-					addrange = DatumGetBool(add);
-					if (!addrange)
-						break;
+					if (consistentFn[attno - 1].fn_nargs >= 4)
+					{
+						/* Check all keys at once */
+						add = FunctionCall4Coll(&consistentFn[attno - 1],
+												collation,
+												PointerGetDatum(bdesc),
+												PointerGetDatum(bval),
+												PointerGetDatum(keys[attno - 1]),
+												Int32GetDatum(nkeys[attno - 1]));
+						addrange = DatumGetBool(add);
+					}
+					else
+					{
+						/*
+						 * Check keys one by one
+						 *
+						 * When there are multiple scan keys, failure to meet the
+						 * criteria for a single one of them is enough to discard
+						 * the range as a whole, so break out of the loop as soon
+						 * as a false return value is obtained.
+						 */
+						int			keyno;
+
+						for (keyno = 0; keyno < nkeys[attno - 1]; keyno++)
+						{
+							add = FunctionCall3Coll(&consistentFn[attno - 1],
+													keys[attno - 1][keyno]->sk_collation,
+													PointerGetDatum(bdesc),
+													PointerGetDatum(bval),
+													PointerGetDatum(keys[attno - 1][keyno]));
+							addrange = DatumGetBool(add);
+							if (!addrange)
+								break;
+						}
+					}
 				}
 			}
 		}

src/backend/access/brin/brin_inclusion.c

@@ -85,8 +85,6 @@ static FmgrInfo *inclusion_get_procinfo(BrinDesc *bdesc, uint16 attno,
 										uint16 procnum);
 static FmgrInfo *inclusion_get_strategy_procinfo(BrinDesc *bdesc, uint16 attno,
 												 Oid subtype, uint16 strategynum);
-static bool inclusion_consistent_key(BrinDesc *bdesc, BrinValues *column,
-									 ScanKey key, Oid colloid);
 
 
 /*
@@ -243,9 +241,9 @@ brin_inclusion_add_value(PG_FUNCTION_ARGS)
 /*
  * BRIN inclusion consistent function
  *
- * We inspect the IS NULL scan keys first, which allows us to make a decision
- * without looking at the contents of the page range. Only when the page range
- * matches the IS NULL keys, we check the regular scan keys.
+ * We're no longer dealing with NULL keys in the consistent function, that is
+ * now handled by the AM code. That means we should not get any all-NULL ranges
+ * either, because those can't be consistent with regular (not [IS] NULL) keys.
  *
  * All of the strategies are optional.
  */
@@ -254,63 +252,29 @@ brin_inclusion_consistent(PG_FUNCTION_ARGS)
 {
 	BrinDesc   *bdesc = (BrinDesc *) PG_GETARG_POINTER(0);
 	BrinValues *column = (BrinValues *) PG_GETARG_POINTER(1);
-	ScanKey    *keys = (ScanKey *) PG_GETARG_POINTER(2);
-	int			nkeys = PG_GETARG_INT32(3);
-	Oid			colloid = PG_GET_COLLATION();
-	int			keyno;
+	ScanKey		key = (ScanKey) PG_GETARG_POINTER(2);
+	Oid			colloid = PG_GET_COLLATION(),
+				subtype;
+	Datum		unionval;
+	AttrNumber	attno;
+	Datum		query;
+	FmgrInfo   *finfo;
+	Datum		result;
 
-	/* make sure we got some scan keys */
-	Assert((nkeys > 0) && (keys != NULL));
+	/* This opclass uses the old signature with only three arguments. */
+	Assert(PG_NARGS() == 3);
 
-	/*
-	 * If is all nulls, it cannot possibly be consistent (at this point we
-	 * know there are at least some regular scan keys).
-	 */
-	if (column->bv_allnulls)
-		PG_RETURN_BOOL(false);
+	/* Should not be dealing with all-NULL ranges. */
+	Assert(!column->bv_allnulls);
 
 	/* It has to be checked, if it contains elements that are not mergeable. */
 	if (DatumGetBool(column->bv_values[INCLUSION_UNMERGEABLE]))
 		PG_RETURN_BOOL(true);
 
-	/* Check that the range is consistent with all regular scan keys. */
-	for (keyno = 0; keyno < nkeys; keyno++)
-	{
-		ScanKey		key = keys[keyno];
-
-		/* NULL keys are handled and filtered-out in bringetbitmap */
-		Assert(!(key->sk_flags & SK_ISNULL));
-
-		/*
-		 * When there are multiple scan keys, failure to meet the criteria for
-		 * a single one of them is enough to discard the range as a whole, so
-		 * break out of the loop as soon as a false return value is obtained.
-		 */
-		if (!inclusion_consistent_key(bdesc, column, key, colloid))
-			PG_RETURN_BOOL(false);
-	}
-
-	PG_RETURN_BOOL(true);
-}
-
-/*
- * inclusion_consistent_key
- *		Determine if the range is consistent with a single scan key.
- */
-static bool
-inclusion_consistent_key(BrinDesc *bdesc, BrinValues *column, ScanKey key,
-						 Oid colloid)
-{
-	FmgrInfo   *finfo;
-	AttrNumber	attno = key->sk_attno;
-	Oid			subtype = key->sk_subtype;
-	Datum		query = key->sk_argument;
-	Datum		unionval = column->bv_values[INCLUSION_UNION];
-	Datum		result;
-
-	/* This should be called only for regular keys, not for IS [NOT] NULL. */
-	Assert(!(key->sk_flags & SK_ISNULL));
-
+	attno = key->sk_attno;
+	subtype = key->sk_subtype;
+	query = key->sk_argument;
+	unionval = column->bv_values[INCLUSION_UNION];
 	switch (key->sk_strategy)
 	{
 			/*
@@ -330,49 +294,49 @@ inclusion_consistent_key(BrinDesc *bdesc, BrinValues *column, ScanKey key,
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTOverRightStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 		case RTOverLeftStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTRightStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 		case RTOverRightStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTLeftStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 		case RTRightStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTOverLeftStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 		case RTBelowStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTOverAboveStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 		case RTOverBelowStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTAboveStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 		case RTOverAboveStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTBelowStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 		case RTAboveStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTOverBelowStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 			/*
 			 * Overlap and contains strategies
@@ -390,7 +354,7 @@ inclusion_consistent_key(BrinDesc *bdesc, BrinValues *column, ScanKey key,
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													key->sk_strategy);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return DatumGetBool(result);
+			PG_RETURN_DATUM(result);
 
 			/*
 			 * Contained by strategies
@@ -410,9 +374,9 @@ inclusion_consistent_key(BrinDesc *bdesc, BrinValues *column, ScanKey key,
 													RTOverlapStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
 			if (DatumGetBool(result))
-				return true;
+				PG_RETURN_BOOL(true);
 
-			return DatumGetBool(column->bv_values[INCLUSION_CONTAINS_EMPTY]);
+			PG_RETURN_DATUM(column->bv_values[INCLUSION_CONTAINS_EMPTY]);
 
 			/*
 			 * Adjacent strategy
@@ -429,12 +393,12 @@ inclusion_consistent_key(BrinDesc *bdesc, BrinValues *column, ScanKey key,
 													RTOverlapStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
 			if (DatumGetBool(result))
-				return true;
+				PG_RETURN_BOOL(true);
 
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTAdjacentStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return DatumGetBool(result);
+			PG_RETURN_DATUM(result);
 
 			/*
 			 * Basic comparison strategies
@@ -464,40 +428,40 @@ inclusion_consistent_key(BrinDesc *bdesc, BrinValues *column, ScanKey key,
 													RTRightStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
 			if (!DatumGetBool(result))
-				return true;
+				PG_RETURN_BOOL(true);
 
-			return DatumGetBool(column->bv_values[INCLUSION_CONTAINS_EMPTY]);
+			PG_RETURN_DATUM(column->bv_values[INCLUSION_CONTAINS_EMPTY]);
 
 		case RTSameStrategyNumber:
 		case RTEqualStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTContainsStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
 			if (DatumGetBool(result))
-				return true;
+				PG_RETURN_BOOL(true);
 
-			return DatumGetBool(column->bv_values[INCLUSION_CONTAINS_EMPTY]);
+			PG_RETURN_DATUM(column->bv_values[INCLUSION_CONTAINS_EMPTY]);
 
 		case RTGreaterEqualStrategyNumber:
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTLeftStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
 			if (!DatumGetBool(result))
-				return true;
+				PG_RETURN_BOOL(true);
 
-			return DatumGetBool(column->bv_values[INCLUSION_CONTAINS_EMPTY]);
+			PG_RETURN_DATUM(column->bv_values[INCLUSION_CONTAINS_EMPTY]);
 
 		case RTGreaterStrategyNumber:
 			/* no need to check for empty elements */
 			finfo = inclusion_get_strategy_procinfo(bdesc, attno, subtype,
 													RTLeftStrategyNumber);
 			result = FunctionCall2Coll(finfo, colloid, unionval, query);
-			return !DatumGetBool(result);
+			PG_RETURN_BOOL(!DatumGetBool(result));
 
 		default:
 			/* shouldn't happen */
 			elog(ERROR, "invalid strategy number %d", key->sk_strategy);
-			return false;
+			PG_RETURN_BOOL(false);
 	}
 }