Feedback-ID: i0fe9450f:Fastmail
Date: Tue, 14 Apr 2026 02:13:52 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Andres Freund <andres@anarazel.de>
Cc: Postgres hackers <pgsql-hackers@lists.postgresql.org>,
	Andrew Dunstan <andrew@dunslane.net>
Subject: Re: test_compression, test module for low-level compression APIs
 (for 2b5ba2a0a141)
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On Mon, Apr 13, 2026 at 10:08:16AM -0400, Andres Freund wrote:
> I guess that'd work.  I don't really see the point in calling these via SQL,
> tbh, but if that's easier for you, using a regress.c helper woul do the trick.

Okay, thanks for the opinion.  It makes the addition of more tests
slightly easier as there is no need to rely on an extra wrapper of
what's in pg_lzcompress.h.  I have done that in the attached, with
additions to the main regression test suite.
--
Michael

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=46rom ad27ede8a798c264de961b8bc37205a2635e43c5 Mon Sep 17 00:00:00 2001
=46rom: Michael Paquier <michael@paquier.xyz>
Date: Tue, 14 Apr 2026 02:01:26 +0900
Subject: [PATCH v2] Add tests for low-level PGLZ compression

The goal of this module is to provide an entry point for the coverage of
for low-level APIs of compression and decompression of PGLZ.

This includes tests for the cases detected by fuzzing related to
corrupted data, as fixed in 2b5ba2a0a141:
- Control byte with match tag bit set, where no data follows.
- Control byte with match tag bit set, where 1 byte follows.
- Extension byte needed (len=3D18), where no data follows.

As bonus points, tests are added for compress/decompress roundtrips, and
for check_complete=3Dfalse/true.

Backpatch-through: 14
---
 .../regress/expected/compression_pglz.out     | 62 +++++++++++++++++
 src/test/regress/parallel_schedule            |  2 +-
 src/test/regress/regress.c                    | 66 +++++++++++++++++++
 src/test/regress/sql/compression_pglz.sql     | 49 ++++++++++++++
 4 files changed, 178 insertions(+), 1 deletion(-)
 create mode 100644 src/test/regress/expected/compression_pglz.out
 create mode 100644 src/test/regress/sql/compression_pglz.sql

diff --git a/src/test/regress/expected/compression_pglz.out b/src/test/regr=
ess/expected/compression_pglz.out
new file mode 100644
index 000000000000..daf457f4ac0a
--- /dev/null
+++ b/src/test/regress/expected/compression_pglz.out
@@ -0,0 +1,62 @@
+--
+-- Tests for PGLZ compression
+--
+-- directory paths and dlsuffix are passed to us in environment variables
+\getenv libdir PG_LIBDIR
+\getenv dlsuffix PG_DLSUFFIX
+\set regresslib :libdir '/regress' :dlsuffix
+CREATE FUNCTION test_pglz_compress(bytea)
+  RETURNS bytea
+  AS :'regresslib' LANGUAGE C STRICT;
+CREATE FUNCTION test_pglz_decompress(bytea, int4, bool)
+  RETURNS bytea
+  AS :'regresslib' LANGUAGE C STRICT;
+-- Round-trip with pglz: compress then decompress.
+SELECT test_pglz_decompress(test_pglz_compress(
+    decode(repeat('abcd', 100), 'escape')), 400, false) =3D
+    decode(repeat('abcd', 100), 'escape') AS roundtrip_ok;
+ roundtrip_ok=20
+--------------
+ t
+(1 row)
+
+SELECT test_pglz_decompress(test_pglz_compress(
+    decode(repeat('abcd', 100), 'escape')), 400, true) =3D
+    decode(repeat('abcd', 100), 'escape') AS roundtrip_ok;
+ roundtrip_ok=20
+--------------
+ t
+(1 row)
+
+-- Decompression with rawsize too large, fails to fill the destination
+-- buffer.
+SELECT test_pglz_decompress(test_pglz_compress(
+    decode(repeat('abcd', 100), 'escape')), 500, true);
+ERROR:  pglz_decompress failed
+-- Decompression with rawsize too small, fails with source not fully
+-- consumed.
+SELECT test_pglz_decompress(test_pglz_compress(
+    decode(repeat('abcd', 100), 'escape')), 100, true);
+ERROR:  pglz_decompress failed
+-- Corrupted compressed data.  The control byte is set with match tag bit,
+-- but only 1 byte follows.
+SELECT test_pglz_decompress('\x01ff'::bytea, 1024, false);
+ERROR:  pglz_decompress failed
+SELECT test_pglz_decompress('\x01ff'::bytea, 1024, true);
+ERROR:  pglz_decompress failed
+-- Corrupted compressed data.  Control byte with match tag bit set, where
+-- no data follows.
+SELECT length(test_pglz_decompress('\x01'::bytea, 1024, false)) AS ctrl_on=
ly_len;
+ ctrl_only_len=20
+---------------
+             0
+(1 row)
+
+SELECT test_pglz_decompress('\x01'::bytea, 1024, true);
+ERROR:  pglz_decompress failed
+-- Corrupted compressed data.  The match tag encodes len=3D18 (aka the
+-- extension byte is needed) but there is no data.
+SELECT test_pglz_decompress('\x010f01'::bytea, 1024, false);
+ERROR:  pglz_decompress failed
+SELECT test_pglz_decompress('\x010f01'::bytea, 1024, true);
+ERROR:  pglz_decompress failed
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel=
_schedule
index cc365393bb7d..3b059906161f 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -128,7 +128,7 @@ test: partition_merge partition_split partition_join pa=
rtition_prune reloptions
 # event_trigger depends on create_am and cannot run concurrently with
 # any test that runs DDL
 # oidjoins is read-only, though, and should run late for best coverage
-test: oidjoins event_trigger
+test: oidjoins event_trigger compression_pglz
=20
 test: role_ddl tablespace_ddl database_ddl
=20
diff --git a/src/test/regress/regress.c b/src/test/regress/regress.c
index 5c19f70b6e8e..2bcb5559a452 100644
--- a/src/test/regress/regress.c
+++ b/src/test/regress/regress.c
@@ -27,6 +27,7 @@
 #include "catalog/pg_type.h"
 #include "commands/sequence.h"
 #include "commands/trigger.h"
+#include "common/pg_lzcompress.h"
 #include "executor/executor.h"
 #include "executor/functions.h"
 #include "executor/spi.h"
@@ -1422,3 +1423,68 @@ test_instr_time(PG_FUNCTION_ARGS)
=20
 	PG_RETURN_BOOL(true);
 }
+
+/*
+ * test_pglz_compress
+ *
+ * Compress the input using pglz_compress().  Only the "always" strategy is
+ * currently supported.
+ *
+ * Returns the compressed data, or NULL if compression fails.
+ */
+PG_FUNCTION_INFO_V1(test_pglz_compress);
+Datum
+test_pglz_compress(PG_FUNCTION_ARGS)
+{
+	bytea	   *input =3D PG_GETARG_BYTEA_PP(0);
+	char	   *source =3D VARDATA_ANY(input);
+	int32		slen =3D VARSIZE_ANY_EXHDR(input);
+	int32		maxout =3D PGLZ_MAX_OUTPUT(slen);
+	bytea	   *result;
+	int32		clen;
+
+	result =3D (bytea *) palloc(maxout + VARHDRSZ);
+	clen =3D pglz_compress(source, slen, VARDATA(result),
+						 PGLZ_strategy_always);
+	if (clen < 0)
+		PG_RETURN_NULL();
+
+	SET_VARSIZE(result, clen + VARHDRSZ);
+	PG_RETURN_BYTEA_P(result);
+}
+
+/*
+ * test_pglz_decompress
+ *
+ * Decompress the input using pglz_decompress().
+ *
+ * The second argument is the expected uncompressed data size.  The third
+ * argument is here for the check_complete flag.
+ *
+ * Returns the decompressed data, or raises an error if decompression fail=
s.
+ */
+PG_FUNCTION_INFO_V1(test_pglz_decompress);
+Datum
+test_pglz_decompress(PG_FUNCTION_ARGS)
+{
+	bytea	   *input =3D PG_GETARG_BYTEA_PP(0);
+	int32		rawsize =3D PG_GETARG_INT32(1);
+	bool		check_complete =3D PG_GETARG_BOOL(2);
+	char	   *source =3D VARDATA_ANY(input);
+	int32		slen =3D VARSIZE_ANY_EXHDR(input);
+	bytea	   *result;
+	int32		dlen;
+
+	if (rawsize < 0)
+		elog(ERROR, "rawsize must not be negative");
+
+	result =3D (bytea *) palloc(rawsize + VARHDRSZ);
+
+	dlen =3D pglz_decompress(source, slen, VARDATA(result),
+						   rawsize, check_complete);
+	if (dlen < 0)
+		elog(ERROR, "pglz_decompress failed");
+
+	SET_VARSIZE(result, dlen + VARHDRSZ);
+	PG_RETURN_BYTEA_P(result);
+}
diff --git a/src/test/regress/sql/compression_pglz.sql b/src/test/regress/s=
ql/compression_pglz.sql
new file mode 100644
index 000000000000..115f1300d748
--- /dev/null
+++ b/src/test/regress/sql/compression_pglz.sql
@@ -0,0 +1,49 @@
+--
+-- Tests for PGLZ compression
+--
+
+-- directory paths and dlsuffix are passed to us in environment variables
+\getenv libdir PG_LIBDIR
+\getenv dlsuffix PG_DLSUFFIX
+
+\set regresslib :libdir '/regress' :dlsuffix
+
+CREATE FUNCTION test_pglz_compress(bytea)
+  RETURNS bytea
+  AS :'regresslib' LANGUAGE C STRICT;
+CREATE FUNCTION test_pglz_decompress(bytea, int4, bool)
+  RETURNS bytea
+  AS :'regresslib' LANGUAGE C STRICT;
+
+-- Round-trip with pglz: compress then decompress.
+SELECT test_pglz_decompress(test_pglz_compress(
+    decode(repeat('abcd', 100), 'escape')), 400, false) =3D
+    decode(repeat('abcd', 100), 'escape') AS roundtrip_ok;
+SELECT test_pglz_decompress(test_pglz_compress(
+    decode(repeat('abcd', 100), 'escape')), 400, true) =3D
+    decode(repeat('abcd', 100), 'escape') AS roundtrip_ok;
+
+-- Decompression with rawsize too large, fails to fill the destination
+-- buffer.
+SELECT test_pglz_decompress(test_pglz_compress(
+    decode(repeat('abcd', 100), 'escape')), 500, true);
+
+-- Decompression with rawsize too small, fails with source not fully
+-- consumed.
+SELECT test_pglz_decompress(test_pglz_compress(
+    decode(repeat('abcd', 100), 'escape')), 100, true);
+
+-- Corrupted compressed data.  The control byte is set with match tag bit,
+-- but only 1 byte follows.
+SELECT test_pglz_decompress('\x01ff'::bytea, 1024, false);
+SELECT test_pglz_decompress('\x01ff'::bytea, 1024, true);
+
+-- Corrupted compressed data.  Control byte with match tag bit set, where
+-- no data follows.
+SELECT length(test_pglz_decompress('\x01'::bytea, 1024, false)) AS ctrl_on=
ly_len;
+SELECT test_pglz_decompress('\x01'::bytea, 1024, true);
+
+-- Corrupted compressed data.  The match tag encodes len=3D18 (aka the
+-- extension byte is needed) but there is no data.
+SELECT test_pglz_decompress('\x010f01'::bytea, 1024, false);
+SELECT test_pglz_decompress('\x010f01'::bytea, 1024, true);
--=20
2.53.0


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