Add Bloom filter implementation.

A Bloom filter is a space-efficient, probabilistic data structure that
can be used to test set membership.  Callers will sometimes incur false
positives, but never false negatives.  The rate of false positives is a
function of the total number of elements and the amount of memory
available for the Bloom filter.

Two classic applications of Bloom filters are cache filtering, and data
synchronization testing.  Any user of Bloom filters must accept the
possibility of false positives as a cost worth paying for the benefit in
space efficiency.

This commit adds a test harness extension module, test_bloomfilter.  It
can be used to get a sense of how the Bloom filter implementation
performs under varying conditions.

This is infrastructure for the upcoming "heapallindexed" amcheck patch,
which verifies the consistency of a heap relation against one of its
indexes.

Author: Peter Geoghegan
Reviewed-By: Andrey Borodin, Michael Paquier, Thomas Munro, Andres Freund
Discussion: https://postgr.es/m/CAH2-Wzm5VmG7cu1N-H=nnS57wZThoSDQU+F5dewx3o84M+jY=g@mail.gmail.com

src/backend/lib/Makefile

@@ -12,7 +12,7 @@ subdir = src/backend/lib
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-OBJS = binaryheap.o bipartite_match.o dshash.o hyperloglog.o ilist.o \
-	   knapsack.o pairingheap.o rbtree.o stringinfo.o
+OBJS = binaryheap.o bipartite_match.o bloomfilter.o dshash.o hyperloglog.o \
+       ilist.o knapsack.o pairingheap.o rbtree.o stringinfo.o
 
 include $(top_srcdir)/src/backend/common.mk

src/backend/lib/README

@@ -3,6 +3,8 @@ in the backend:
 
 binaryheap.c - a binary heap
 
+bloomfilter.c - probabilistic, space-efficient set membership testing
+
 hyperloglog.c - a streaming cardinality estimator
 
 pairingheap.c - a pairing heap

src/backend/lib/bloomfilter.c

@@ -0,0 +1,305 @@
+/*-------------------------------------------------------------------------
+ *
+ * bloomfilter.c
+ *		Space-efficient set membership testing
+ *
+ * A Bloom filter is a probabilistic data structure that is used to test an
+ * element's membership of a set.  False positives are possible, but false
+ * negatives are not; a test of membership of the set returns either "possibly
+ * in set" or "definitely not in set".  This is typically very space efficient,
+ * which can be a decisive advantage.
+ *
+ * Elements can be added to the set, but not removed.  The more elements that
+ * are added, the larger the probability of false positives.  Caller must hint
+ * an estimated total size of the set when the Bloom filter is initialized.
+ * This is used to balance the use of memory against the final false positive
+ * rate.
+ *
+ * The implementation is well suited to data synchronization problems between
+ * unordered sets, especially where predictable performance is important and
+ * some false positives are acceptable.  It's also well suited to cache
+ * filtering problems where a relatively small and/or low cardinality set is
+ * fingerprinted, especially when many subsequent membership tests end up
+ * indicating that values of interest are not present.  That should save the
+ * caller many authoritative lookups, such as expensive probes of a much larger
+ * on-disk structure.
+ *
+ * Copyright (c) 2018, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/lib/bloomfilter.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <math.h>
+
+#include "access/hash.h"
+#include "lib/bloomfilter.h"
+
+#define MAX_HASH_FUNCS		10
+
+struct bloom_filter
+{
+	/* K hash functions are used, seeded by caller's seed */
+	int			k_hash_funcs;
+	uint64		seed;
+	/* m is bitset size, in bits.  Must be a power of two <= 2^32.  */
+	uint64		m;
+	unsigned char bitset[FLEXIBLE_ARRAY_MEMBER];
+};
+
+static int	my_bloom_power(uint64 target_bitset_bits);
+static int	optimal_k(uint64 bitset_bits, int64 total_elems);
+static void k_hashes(bloom_filter *filter, uint32 *hashes, unsigned char *elem,
+		 size_t len);
+static inline uint32 mod_m(uint32 a, uint64 m);
+
+/*
+ * Create Bloom filter in caller's memory context.  We aim for a false positive
+ * rate of between 1% and 2% when bitset size is not constrained by memory
+ * availability.
+ *
+ * total_elems is an estimate of the final size of the set.  It should be
+ * approximately correct, but the implementation can cope well with it being
+ * off by perhaps a factor of five or more.  See "Bloom Filters in
+ * Probabilistic Verification" (Dillinger & Manolios, 2004) for details of why
+ * this is the case.
+ *
+ * bloom_work_mem is sized in KB, in line with the general work_mem convention.
+ * This determines the size of the underlying bitset (trivial bookkeeping space
+ * isn't counted).  The bitset is always sized as a power of two number of
+ * bits, and the largest possible bitset is 512MB (2^32 bits).  The
+ * implementation allocates only enough memory to target its standard false
+ * positive rate, using a simple formula with caller's total_elems estimate as
+ * an input.  The bitset might be as small as 1MB, even when bloom_work_mem is
+ * much higher.
+ *
+ * The Bloom filter is seeded using a value provided by the caller.  Using a
+ * distinct seed value on every call makes it unlikely that the same false
+ * positives will reoccur when the same set is fingerprinted a second time.
+ * Callers that don't care about this pass a constant as their seed, typically
+ * 0.  Callers can use a pseudo-random seed in the range of 0 - INT_MAX by
+ * calling random().
+ */
+bloom_filter *
+bloom_create(int64 total_elems, int bloom_work_mem, uint64 seed)
+{
+	bloom_filter *filter;
+	int			bloom_power;
+	uint64		bitset_bytes;
+	uint64		bitset_bits;
+
+	/*
+	 * Aim for two bytes per element; this is sufficient to get a false
+	 * positive rate below 1%, independent of the size of the bitset or total
+	 * number of elements.  Also, if rounding down the size of the bitset to
+	 * the next lowest power of two turns out to be a significant drop, the
+	 * false positive rate still won't exceed 2% in almost all cases.
+	 */
+	bitset_bytes = Min(bloom_work_mem * UINT64CONST(1024), total_elems * 2);
+	bitset_bytes = Max(1024 * 1024, bitset_bytes);
+
+	/*
+	 * Size in bits should be the highest power of two <= target.  bitset_bits
+	 * is uint64 because PG_UINT32_MAX is 2^32 - 1, not 2^32
+	 */
+	bloom_power = my_bloom_power(bitset_bytes * BITS_PER_BYTE);
+	bitset_bits = UINT64CONST(1) << bloom_power;
+	bitset_bytes = bitset_bits / BITS_PER_BYTE;
+
+	/* Allocate bloom filter with unset bitset */
+	filter = palloc0(offsetof(bloom_filter, bitset) +
+					 sizeof(unsigned char) * bitset_bytes);
+	filter->k_hash_funcs = optimal_k(bitset_bits, total_elems);
+	filter->seed = seed;
+	filter->m = bitset_bits;
+
+	return filter;
+}
+
+/*
+ * Free Bloom filter
+ */
+void
+bloom_free(bloom_filter *filter)
+{
+	pfree(filter);
+}
+
+/*
+ * Add element to Bloom filter
+ */
+void
+bloom_add_element(bloom_filter *filter, unsigned char *elem, size_t len)
+{
+	uint32		hashes[MAX_HASH_FUNCS];
+	int			i;
+
+	k_hashes(filter, hashes, elem, len);
+
+	/* Map a bit-wise address to a byte-wise address + bit offset */
+	for (i = 0; i < filter->k_hash_funcs; i++)
+	{
+		filter->bitset[hashes[i] >> 3] |= 1 << (hashes[i] & 7);
+	}
+}
+
+/*
+ * Test if Bloom filter definitely lacks element.
+ *
+ * Returns true if the element is definitely not in the set of elements
+ * observed by bloom_add_element().  Otherwise, returns false, indicating that
+ * element is probably present in set.
+ */
+bool
+bloom_lacks_element(bloom_filter *filter, unsigned char *elem, size_t len)
+{
+	uint32		hashes[MAX_HASH_FUNCS];
+	int			i;
+
+	k_hashes(filter, hashes, elem, len);
+
+	/* Map a bit-wise address to a byte-wise address + bit offset */
+	for (i = 0; i < filter->k_hash_funcs; i++)
+	{
+		if (!(filter->bitset[hashes[i] >> 3] & (1 << (hashes[i] & 7))))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * What proportion of bits are currently set?
+ *
+ * Returns proportion, expressed as a multiplier of filter size.  That should
+ * generally be close to 0.5, even when we have more than enough memory to
+ * ensure a false positive rate within target 1% to 2% band, since more hash
+ * functions are used as more memory is available per element.
+ *
+ * This is the only instrumentation that is low overhead enough to appear in
+ * debug traces.  When debugging Bloom filter code, it's likely to be far more
+ * interesting to directly test the false positive rate.
+ */
+double
+bloom_prop_bits_set(bloom_filter *filter)
+{
+	int			bitset_bytes = filter->m / BITS_PER_BYTE;
+	uint64		bits_set = 0;
+	int			i;
+
+	for (i = 0; i < bitset_bytes; i++)
+	{
+		unsigned char byte = filter->bitset[i];
+
+		while (byte)
+		{
+			bits_set++;
+			byte &= (byte - 1);
+		}
+	}
+
+	return bits_set / (double) filter->m;
+}
+
+/*
+ * Which element in the sequence of powers of two is less than or equal to
+ * target_bitset_bits?
+ *
+ * Value returned here must be generally safe as the basis for actual bitset
+ * size.
+ *
+ * Bitset is never allowed to exceed 2 ^ 32 bits (512MB).  This is sufficient
+ * for the needs of all current callers, and allows us to use 32-bit hash
+ * functions.  It also makes it easy to stay under the MaxAllocSize restriction
+ * (caller needs to leave room for non-bitset fields that appear before
+ * flexible array member, so a 1GB bitset would use an allocation that just
+ * exceeds MaxAllocSize).
+ */
+static int
+my_bloom_power(uint64 target_bitset_bits)
+{
+	int			bloom_power = -1;
+
+	while (target_bitset_bits > 0 && bloom_power < 32)
+	{
+		bloom_power++;
+		target_bitset_bits >>= 1;
+	}
+
+	return bloom_power;
+}
+
+/*
+ * Determine optimal number of hash functions based on size of filter in bits,
+ * and projected total number of elements.  The optimal number is the number
+ * that minimizes the false positive rate.
+ */
+static int
+optimal_k(uint64 bitset_bits, int64 total_elems)
+{
+	int			k = round(log(2.0) * bitset_bits / total_elems);
+
+	return Max(1, Min(k, MAX_HASH_FUNCS));
+}
+
+/*
+ * Generate k hash values for element.
+ *
+ * Caller passes array, which is filled-in with k values determined by hashing
+ * caller's element.
+ *
+ * Only 2 real independent hash functions are actually used to support an
+ * interface of up to MAX_HASH_FUNCS hash functions; enhanced double hashing is
+ * used to make this work.  The main reason we prefer enhanced double hashing
+ * to classic double hashing is that the latter has an issue with collisions
+ * when using power of two sized bitsets.  See Dillinger & Manolios for full
+ * details.
+ */
+static void
+k_hashes(bloom_filter *filter, uint32 *hashes, unsigned char *elem, size_t len)
+{
+	uint64		hash;
+	uint32		x, y;
+	uint64		m;
+	int			i;
+
+	/* Use 64-bit hashing to get two independent 32-bit hashes */
+	hash = DatumGetUInt64(hash_any_extended(elem, len, filter->seed));
+	x = (uint32) hash;
+	y = (uint32) (hash >> 32);
+	m = filter->m;
+
+	x = mod_m(x, m);
+	y = mod_m(y, m);
+
+	/* Accumulate hashes */
+	hashes[0] = x;
+	for (i = 1; i < filter->k_hash_funcs; i++)
+	{
+		x = mod_m(x + y, m);
+		y = mod_m(y + i, m);
+
+		hashes[i] = x;
+	}
+}
+
+/*
+ * Calculate "val MOD m" inexpensively.
+ *
+ * Assumes that m (which is bitset size) is a power of two.
+ *
+ * Using a power of two number of bits for bitset size allows us to use bitwise
+ * AND operations to calculate the modulo of a hash value.  It's also a simple
+ * way of avoiding the modulo bias effect.
+ */
+static inline uint32
+mod_m(uint32 val, uint64 m)
+{
+	Assert(m <= PG_UINT32_MAX + UINT64CONST(1));
+	Assert(((m - 1) & m) == 0);
+
+	return val & (m - 1);
+}

src/include/lib/bloomfilter.h

@@ -0,0 +1,27 @@
+/*-------------------------------------------------------------------------
+ *
+ * bloomfilter.h
+ *	  Space-efficient set membership testing
+ *
+ * Copyright (c) 2018, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *    src/include/lib/bloomfilter.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef BLOOMFILTER_H
+#define BLOOMFILTER_H
+
+typedef struct bloom_filter bloom_filter;
+
+extern bloom_filter *bloom_create(int64 total_elems, int bloom_work_mem,
+			 uint64 seed);
+extern void bloom_free(bloom_filter *filter);
+extern void bloom_add_element(bloom_filter *filter, unsigned char *elem,
+				  size_t len);
+extern bool bloom_lacks_element(bloom_filter *filter, unsigned char *elem,
+					size_t len);
+extern double bloom_prop_bits_set(bloom_filter *filter);
+
+#endif							/* BLOOMFILTER_H */

src/test/modules/Makefile

@@ -9,6 +9,7 @@ SUBDIRS = \
 		  commit_ts \
 		  dummy_seclabel \
 		  snapshot_too_old \
+		  test_bloomfilter \
 		  test_ddl_deparse \
 		  test_extensions \
 		  test_parser \

src/test/modules/test_bloomfilter/.gitignore

@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/

src/test/modules/test_bloomfilter/Makefile

@@ -0,0 +1,21 @@
+# src/test/modules/test_bloomfilter/Makefile
+
+MODULE_big = test_bloomfilter
+OBJS = test_bloomfilter.o $(WIN32RES)
+PGFILEDESC = "test_bloomfilter - test code for Bloom filter library"
+
+EXTENSION = test_bloomfilter
+DATA = test_bloomfilter--1.0.sql
+
+REGRESS = test_bloomfilter
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/test_bloomfilter
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif

src/test/modules/test_bloomfilter/README

@@ -0,0 +1,68 @@
+test_bloomfilter overview
+=========================
+
+test_bloomfilter is a test harness module for testing Bloom filter library set
+membership operations.  It consists of a single SQL-callable function,
+test_bloomfilter(), plus a regression test that calls test_bloomfilter().
+Membership tests are performed against a dataset that the test harness module
+generates.
+
+The test_bloomfilter() function displays instrumentation at DEBUG1 elog level
+(WARNING when the false positive rate exceeds a 1% threshold).  This can be
+used to get a sense of the performance characteristics of the Postgres Bloom
+filter implementation under varied conditions.
+
+Bitset size
+-----------
+
+The main bloomfilter.c criteria for sizing its bitset is that the false
+positive rate should not exceed 2% when sufficient bloom_work_mem is available
+(and the caller-supplied estimate of the number of elements turns out to have
+been accurate).  A 1% - 2% rate is currently assumed to be suitable for all
+Bloom filter callers.
+
+With an optimal K (number of hash functions), Bloom filters should only have a
+1% false positive rate with just 9.6 bits of memory per element.  The Postgres
+implementation's 2% worst case guarantee exists because there is a need for
+some slop due to implementation inflexibility in bitset sizing.  Since the
+bitset size is always actually kept to a power of two number of bits, callers
+can have their bloom_work_mem argument truncated down by almost half.
+In practice, callers that make a point of passing a bloom_work_mem that is an
+exact power of two bitset size (such as test_bloomfilter.c) will actually get
+the "9.6 bits per element" 1% false positive rate.
+
+Testing strategy
+----------------
+
+Our approach to regression testing is to test that a Bloom filter has only a 1%
+false positive rate for a single bitset size (2 ^ 23, or 1MB).  We test a
+dataset with 838,861 elements, which works out at 10 bits of memory per
+element.  We round up from 9.6 bits to 10 bits to make sure that we reliably
+get under 1% for regression testing.  Note that a random seed is used in the
+regression tests because the exact false positive rate is inconsistent across
+platforms.  Inconsistent hash function behavior is something that the
+regression tests need to be tolerant of anyway.
+
+test_bloomfilter() SQL-callable function
+========================================
+
+The SQL-callable function test_bloomfilter() provides the following arguments:
+
+* "power" is the power of two used to size the Bloom filter's bitset.
+
+The minimum valid argument value is 23 (2^23 bits), or 1MB of memory.  The
+maximum valid argument value is 32, or 512MB of memory.
+
+* "nelements" is the number of elements to generate for testing purposes.
+
+* "seed" is a seed value for hashing.
+
+A value < 0 is interpreted as "use random seed".  Varying the seed value (or
+specifying -1) should result in small variations in the total number of false
+positives.
+
+* "tests" is the number of tests to run.
+
+This may be increased when it's useful to perform many tests in an interactive
+session.  It only makes sense to perform multiple tests when a random seed is
+used.

src/test/modules/test_bloomfilter/expected/test_bloomfilter.out

@@ -0,0 +1,22 @@
+CREATE EXTENSION test_bloomfilter;
+-- See README for explanation of arguments:
+SELECT test_bloomfilter(power => 23,
+    nelements => 838861,
+    seed => -1,
+    tests => 1);
+ test_bloomfilter 
+------------------
+ 
+(1 row)
+
+-- Equivalent "10 bits per element" tests for all possible bitset sizes:
+--
+-- SELECT test_bloomfilter(24, 1677722)
+-- SELECT test_bloomfilter(25, 3355443)
+-- SELECT test_bloomfilter(26, 6710886)
+-- SELECT test_bloomfilter(27, 13421773)
+-- SELECT test_bloomfilter(28, 26843546)
+-- SELECT test_bloomfilter(29, 53687091)
+-- SELECT test_bloomfilter(30, 107374182)
+-- SELECT test_bloomfilter(31, 214748365)
+-- SELECT test_bloomfilter(32, 429496730)

src/test/modules/test_bloomfilter/sql/test_bloomfilter.sql

@@ -0,0 +1,19 @@
+CREATE EXTENSION test_bloomfilter;
+
+-- See README for explanation of arguments:
+SELECT test_bloomfilter(power => 23,
+    nelements => 838861,
+    seed => -1,
+    tests => 1);
+
+-- Equivalent "10 bits per element" tests for all possible bitset sizes:
+--
+-- SELECT test_bloomfilter(24, 1677722)
+-- SELECT test_bloomfilter(25, 3355443)
+-- SELECT test_bloomfilter(26, 6710886)
+-- SELECT test_bloomfilter(27, 13421773)
+-- SELECT test_bloomfilter(28, 26843546)
+-- SELECT test_bloomfilter(29, 53687091)
+-- SELECT test_bloomfilter(30, 107374182)
+-- SELECT test_bloomfilter(31, 214748365)
+-- SELECT test_bloomfilter(32, 429496730)

src/test/modules/test_bloomfilter/test_bloomfilter--1.0.sql

@@ -0,0 +1,11 @@
+/* src/test/modules/test_bloomfilter/test_bloomfilter--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION test_bloomfilter" to load this file. \quit
+
+CREATE FUNCTION test_bloomfilter(power integer,
+    nelements bigint,
+    seed integer DEFAULT -1,
+    tests integer DEFAULT 1)
+RETURNS pg_catalog.void STRICT
+AS 'MODULE_PATHNAME' LANGUAGE C;

src/test/modules/test_bloomfilter/test_bloomfilter.c

@@ -0,0 +1,138 @@
+/*--------------------------------------------------------------------------
+ *
+ * test_bloomfilter.c
+ *		Test false positive rate of Bloom filter.
+ *
+ * Copyright (c) 2018, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		src/test/modules/test_bloomfilter/test_bloomfilter.c
+ *
+ * -------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "fmgr.h"
+#include "lib/bloomfilter.h"
+#include "miscadmin.h"
+
+PG_MODULE_MAGIC;
+
+/* Must fit decimal representation of PG_INT64_MAX + 2 bytes: */
+#define MAX_ELEMENT_BYTES		20
+/* False positive rate WARNING threshold (1%): */
+#define FPOSITIVE_THRESHOLD		0.01
+
+
+/*
+ * Populate an empty Bloom filter with "nelements" dummy strings.
+ */
+static void
+populate_with_dummy_strings(bloom_filter *filter, int64 nelements)
+{
+	char		element[MAX_ELEMENT_BYTES];
+	int64		i;
+
+	for (i = 0; i < nelements; i++)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		snprintf(element, sizeof(element), "i" INT64_FORMAT, i);
+		bloom_add_element(filter, (unsigned char *) element, strlen(element));
+	}
+}
+
+/*
+ * Returns number of strings that are indicated as probably appearing in Bloom
+ * filter that were in fact never added by populate_with_dummy_strings().
+ * These are false positives.
+ */
+static int64
+nfalsepos_for_missing_strings(bloom_filter *filter, int64 nelements)
+{
+	char		element[MAX_ELEMENT_BYTES];
+	int64		nfalsepos = 0;
+	int64		i;
+
+	for (i = 0; i < nelements; i++)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		snprintf(element, sizeof(element), "M" INT64_FORMAT, i);
+		if (!bloom_lacks_element(filter, (unsigned char *) element,
+								 strlen(element)))
+			nfalsepos++;
+	}
+
+	return nfalsepos;
+}
+
+static void
+create_and_test_bloom(int power, int64 nelements, int callerseed)
+{
+	int			bloom_work_mem;
+	uint64		seed;
+	int64		nfalsepos;
+	bloom_filter *filter;
+
+	bloom_work_mem = (1L << power) / 8L / 1024L;
+
+	elog(DEBUG1, "bloom_work_mem (KB): %d", bloom_work_mem);
+
+	/*
+	 * Generate random seed, or use caller's.  Seed should always be a
+	 * positive value less than or equal to PG_INT32_MAX, to ensure that any
+	 * random seed can be recreated through callerseed if the need arises.
+	 * (Don't assume that RAND_MAX cannot exceed PG_INT32_MAX.)
+	 */
+	seed = callerseed < 0 ? random() % PG_INT32_MAX : callerseed;
+
+	/* Create Bloom filter, populate it, and report on false positive rate */
+	filter = bloom_create(nelements, bloom_work_mem, seed);
+	populate_with_dummy_strings(filter, nelements);
+	nfalsepos = nfalsepos_for_missing_strings(filter, nelements);
+
+	ereport((nfalsepos > nelements * FPOSITIVE_THRESHOLD) ? WARNING : DEBUG1,
+			(errmsg_internal("seed: " UINT64_FORMAT " false positives: " INT64_FORMAT " (%.6f%%) bitset %.2f%% set" ,
+							 seed, nfalsepos, (double) nfalsepos / nelements,
+							 100.0 * bloom_prop_bits_set(filter))));
+
+	bloom_free(filter);
+}
+
+PG_FUNCTION_INFO_V1(test_bloomfilter);
+
+/*
+ * SQL-callable entry point to perform all tests.
+ *
+ * If a 1% false positive threshold is not met, emits WARNINGs.
+ *
+ * See README for details of arguments.
+ */
+Datum
+test_bloomfilter(PG_FUNCTION_ARGS)
+{
+	int			power = PG_GETARG_INT32(0);
+	int64		nelements = PG_GETARG_INT64(1);
+	int			seed = PG_GETARG_INT32(2);
+	int			tests = PG_GETARG_INT32(3);
+	int			i;
+
+	if (power < 23 || power > 32)
+		elog(ERROR, "power argument must be between 23 and 32 inclusive");
+
+	if (tests <= 0)
+		elog(ERROR, "invalid number of tests: %d", tests);
+
+	if (nelements < 0)
+		elog(ERROR, "invalid number of elements: %d", tests);
+
+	for (i = 0; i < tests; i++)
+	{
+		elog(DEBUG1, "beginning test #%d...", i + 1);
+
+		create_and_test_bloom(power, nelements, seed);
+	}
+
+	PG_RETURN_VOID();
+}

src/test/modules/test_bloomfilter/test_bloomfilter.control

@@ -0,0 +1,4 @@
+comment = 'Test code for Bloom filter library'
+default_version = '1.0'
+module_pathname = '$libdir/test_bloomfilter'
+relocatable = true

src/tools/pgindent/typedefs.list

@@ -2590,6 +2590,7 @@ bitmapword
 bits16
 bits32
 bits8
+bloom_filter
 bool
 brin_column_state
 bytea