On Thu, Nov 27, 2025, at 6:44 AM, Aleksander Alekseev wrote:
> Many thanks for working on this. Unfortunately the patch is
> incomplete. I think we also agreed that lz4 should be opt-out.
>
Aleksander, I missed this point.
Here it is v2. It enforces the lz4 dependency. It works the same as other
dependencies (readline, icu, zlib); error if the dependency could not be found.
Regarding meson, I'm confused. If any of the referred dependencies (icu,
readline, zlib) is not found, there is no hard error. Instead, the feature is
disabled. I searched for a discussion about this decision but couldn't find.
For this patch, I decided to use the same pattern (no error) but I added a
warning message (similar to zlib).
$ meson setup build --prefix=/tmp/pg | grep -i warning
meson.build:1100: WARNING: did not find lz4
meson.build:1675: WARNING: did not find zlib
The other alternative is to always 'enabled' lz4 in meson_options.txt. This
requires you to explicitly enable/disable lz4 if you are using -Dauto_features
option.
Should it report an error (like autoconf) instead of silently disable the
feature that is a requirement? If yes, then we should add error messages for
these 3 dependencies.
$ ./configure --prefix=/tmp/pg
.
.
checking whether to build with ICU support... yes
checking for icu-uc icu-i18n... no
configure: error: Package requirements (icu-uc icu-i18n) were not met:
Package 'icu-uc', required by 'virtual:world', not found
Package 'icu-i18n', required by 'virtual:world', not found
Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.
Alternatively, you may set the environment variables ICU_CFLAGS
and ICU_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.
$ git clean -dfxq
$ meson setup build --prefix=/tmp/pg
.
.
Run-time dependency icu-uc found: NO (tried pkgconfig and cmake)
Run-time dependency icu found: NO (tried cmake)
.
.
Run-time dependency readline found: NO (tried pkgconfig and cmake)
Library readline found: NO
.
.
External libraries
bonjour : NO
bsd_auth : NO
docs : NO
docs_pdf : NO
gss : NO
icu : NO
ldap : NO
libcurl : NO
libnuma : NO
liburing : NO
libxml : NO
libxslt : NO
llvm : NO
lz4 : NO
nls : YES
openssl : NO
pam : NO
plperl : NO 5.40.1
plpython : NO
pltcl : NO
readline : NO
selinux : NO
systemd : NO
uuid : NO
zlib : NO
zstd : NO
User defined options
prefix : /tmp/pg
Found ninja-1.12.1 at /usr/bin/ninja
--
Euler Taveira
EDB https://www.enterprisedb.com/From d700609b2c194e00c7ded6ed9a16dd60427ff846 Mon Sep 17 00:00:00 2001
From: Euler Taveira <[email protected]>
Date: Wed, 26 Nov 2025 12:40:43 -0300
Subject: [PATCH v2] Change default_toast_compression to lz4
The default value for default_toast_compression was pglz. The main
reason is that this option is always available. However, it is known
that pglz uses more CPU than lz4. The default value will be lz4 if lz4
support is built, otherwise, pglz.
---
configure.ac | 2 +-
doc/src/sgml/config.sgml | 3 ++-
doc/src/sgml/installation.sgml | 12 ++++++++++++
meson.build | 2 ++
src/backend/access/common/toast_compression.c | 2 +-
src/backend/utils/misc/guc_parameters.dat | 2 +-
src/bin/initdb/initdb.c | 5 +++++
src/include/access/toast_compression.h | 9 +++++++++
8 files changed, 33 insertions(+), 4 deletions(-)
diff --git a/configure.ac b/configure.ac
index c2413720a18..0a4598e511d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1133,7 +1133,7 @@ AC_SUBST(with_zlib)
# LZ4
#
AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, no, [build with LZ4 support],
+PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
[AC_DEFINE([USE_LZ4], 1, [Define to 1 to build with LZ4 support. (--with-lz4)])])
AC_MSG_RESULT([$with_lz4])
AC_SUBST(with_lz4)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 405c9689bd0..73eb33e2d99 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -9910,7 +9910,8 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
The supported compression methods are <literal>pglz</literal> and
(if <productname>PostgreSQL</productname> was compiled with
<option>--with-lz4</option>) <literal>lz4</literal>.
- The default is <literal>pglz</literal>.
+ The default is <literal>lz4</literal> (if available); otherwise,
+ <literal>pglz</literal>.
</para>
</listitem>
</varlistentry>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index fe8d73e1f8c..f8b43a8cb7b 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -1315,6 +1315,18 @@ build-postgresql:
</listitem>
</varlistentry>
+ <varlistentry id="configure-option-without-lz4">
+ <term><option>--without-lz4</option></term>
+ <listitem>
+ <para>
+ <indexterm>
+ <primary>lz4</primary>
+ </indexterm>
+ Prevents use of the <application>LZ4</application> library.
+ </para>
+ </listitem>
+ </varlistentry>
+
</variablelist>
</sect3>
diff --git a/meson.build b/meson.build
index 6e7ddd74683..1da53bf0138 100644
--- a/meson.build
+++ b/meson.build
@@ -1096,6 +1096,8 @@ if not lz4opt.disabled()
if lz4.found()
cdata.set('USE_LZ4', 1)
cdata.set('HAVE_LIBLZ4', 1)
+ else
+ warning('did not find lz4')
endif
else
diff --git a/src/backend/access/common/toast_compression.c b/src/backend/access/common/toast_compression.c
index 926f1e4008a..4bb29665eab 100644
--- a/src/backend/access/common/toast_compression.c
+++ b/src/backend/access/common/toast_compression.c
@@ -23,7 +23,7 @@
#include "varatt.h"
/* GUC */
-int default_toast_compression = TOAST_PGLZ_COMPRESSION;
+int default_toast_compression = DEFAULT_TOAST_COMPRESSION;
#define NO_COMPRESSION_SUPPORT(method) \
ereport(ERROR, \
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 3b9d8349078..cbe9bf055b3 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -735,7 +735,7 @@
{ name => 'default_toast_compression', type => 'enum', context => 'PGC_USERSET', group => 'CLIENT_CONN_STATEMENT',
short_desc => 'Sets the default compression method for compressible values.',
variable => 'default_toast_compression',
- boot_val => 'TOAST_PGLZ_COMPRESSION',
+ boot_val => 'DEFAULT_TOAST_COMPRESSION',
options => 'default_toast_compression_options',
},
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 92fe2f531f7..92b120d8ab8 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -1424,6 +1424,11 @@ setup_config(void)
"0640", false);
}
+#if USE_LZ4
+ conflines = replace_guc_value(conflines, "default_toast_compression",
+ "lz4", true);
+#endif
+
/*
* Now replace anything that's overridden via -c switches.
*/
diff --git a/src/include/access/toast_compression.h b/src/include/access/toast_compression.h
index 13c4612ceed..7526ea50c5a 100644
--- a/src/include/access/toast_compression.h
+++ b/src/include/access/toast_compression.h
@@ -52,6 +52,15 @@ typedef enum ToastCompressionId
#define CompressionMethodIsValid(cm) ((cm) != InvalidCompressionMethod)
+/*
+ * Choose an appropriate default toast compression method. If lz4 is
+ * compiled-in, use it, otherwise, use pglz.
+ */
+#ifdef USE_LZ4
+#define DEFAULT_TOAST_COMPRESSION TOAST_LZ4_COMPRESSION
+#else
+#define DEFAULT_TOAST_COMPRESSION TOAST_PGLZ_COMPRESSION
+#endif
/* pglz compression/decompression routines */
extern struct varlena *pglz_compress_datum(const struct varlena *value);
--
2.39.5
