Revert "Change default value of default_toast_compression to "lz4""

This reverts commit 7c1849311e, due to the fact that more than 60% of
the buildfarm members do not have lz4 installed.  As we are in the last
commit fest of the development cycle, and that it could take a couple
of weeks to stabilize things, this change is reverted for now.

This commit will be reworked in a lighter version, as
default_toast_compression's default can be changed to "lz4" without the
switch from --with-lz4 to --without-lz4.  This approach will keep the
buildfarm at bay, and still allow builds to take advantage of LZ4 in
TOAST by default, as long as the code is compiled with LZ4 support.

A harder requirement based on LZ4 should be achievable at some point,
but it is going to require some work from the buildfarm owners first.
Perhaps this part could be revisited at the beginning of the next
development cycle.

Discussion: https://postgr.es/m/CAOYmi+meTT0NbLbnVqOJD5OKwCtHL86PQ+RZZTrn6umfmHyWaw@mail.gmail.com

.cirrus.tasks.yml

@@ -984,7 +984,6 @@ task:
         --host=x86_64-w64-mingw32ucrt \
         --enable-cassert \
         --without-icu \
-        --without-lz4 \
         CC="ccache x86_64-w64-mingw32ucrt-gcc" \
         CXX="ccache x86_64-w64-mingw32ucrt-g++"
       make -s -j${BUILD_JOBS} clean

configure

@@ -1603,7 +1603,7 @@ Optional Packages:
   --with-system-tzdata=DIR
                           use system time zone data in DIR
   --without-zlib          do not use Zlib
-  --without-lz4           build without LZ4 support
+  --with-lz4              build with LZ4 support
   --with-zstd             build with ZSTD support
   --with-ssl=LIB          use LIB for SSL/TLS support (openssl)
   --with-openssl          obsolete spelling of --with-ssl=openssl
@@ -9570,9 +9570,7 @@ $as_echo "#define USE_LZ4 1" >>confdefs.h
   esac
 
 else
-  with_lz4=yes
-
-$as_echo "#define USE_LZ4 1" >>confdefs.h
+  with_lz4=no
 
 fi
 

configure.ac

@@ -1188,7 +1188,7 @@ AC_SUBST(with_zlib)
 # LZ4
 #
 AC_MSG_CHECKING([whether to build with LZ4 support])
-PGAC_ARG_BOOL(with, lz4, yes, [build without LZ4 support],
+PGAC_ARG_BOOL(with, lz4, no, [build with 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)

doc/src/sgml/config.sgml

@@ -3498,9 +3498,10 @@ include_dir 'conf.d'
         etc.).
         A compressed page image will be decompressed during WAL replay.
         The supported methods are <literal>pglz</literal>,
-        <literal>lz4</literal> and <literal>zstd</literal> (if
-        <productname>PostgreSQL</productname> was compiled with
-        <option>--with-zstd</option>).
+        <literal>lz4</literal> (if <productname>PostgreSQL</productname>
+        was compiled with <option>--with-lz4</option>) and
+        <literal>zstd</literal> (if <productname>PostgreSQL</productname>
+        was compiled with <option>--with-zstd</option>).
         The default value is <literal>off</literal>.
         Only superusers and users with the appropriate <literal>SET</literal>
         privilege can change this setting.
@@ -10017,9 +10018,9 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         <command>CREATE TABLE</command> or
         <command>ALTER TABLE</command>.)
         The supported compression methods are <literal>pglz</literal> and
-        <literal>lz4</literal>.
-        The default is <literal>lz4</literal> (if available); otherwise,
-        <literal>pglz</literal>.
+        (if <productname>PostgreSQL</productname> was compiled with
+        <option>--with-lz4</option>) <literal>lz4</literal>.
+        The default is <literal>pglz</literal>.
        </para>
       </listitem>
      </varlistentry>

doc/src/sgml/installation.sgml

@@ -975,6 +975,15 @@ build-postgresql:
        </listitem>
       </varlistentry>
 
+      <varlistentry id="configure-option-with-lz4">
+       <term><option>--with-lz4</option></term>
+       <listitem>
+        <para>
+         Build with <productname>LZ4</productname> compression support.
+        </para>
+       </listitem>
+      </varlistentry>
+
       <varlistentry id="configure-option-with-zstd">
        <term><option>--with-zstd</option></term>
        <listitem>
@@ -1306,18 +1315,6 @@ 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>

doc/src/sgml/ref/alter_table.sgml

@@ -462,7 +462,9 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       its existing compression method, rather than being recompressed with the
       compression method of the target column.
       The supported compression
-      methods are <literal>pglz</literal> and <literal>lz4</literal>.  In
+      methods are <literal>pglz</literal> and <literal>lz4</literal>.
+      (<literal>lz4</literal> is available only if <option>--with-lz4</option>
+      was used when building <productname>PostgreSQL</productname>.)  In
       addition, <replaceable class="parameter">compression_method</replaceable>
       can be <literal>default</literal>, which selects the default behavior of
       consulting the <xref linkend="guc-default-toast-compression"/> setting

doc/src/sgml/ref/create_table.sgml

@@ -344,7 +344,9 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       has no direct effect, because such tables have no storage of their own,
       but the configured value will be inherited by newly-created partitions.
       The supported compression methods are <literal>pglz</literal> and
-      <literal>lz4</literal>.  In addition,
+      <literal>lz4</literal>.  (<literal>lz4</literal> is available only if
+      <option>--with-lz4</option> was used when building
+      <productname>PostgreSQL</productname>.)  In addition,
       <replaceable class="parameter">compression_method</replaceable>
       can be <literal>default</literal> to explicitly specify the default
       behavior, which is to consult the

doc/src/sgml/ref/pg_receivewal.sgml

@@ -275,7 +275,9 @@ PostgreSQL documentation
        </para>
        <para>
         The compression method can be set to <literal>gzip</literal>,
-        <literal>lz4</literal> or <literal>none</literal> for no compression.
+        <literal>lz4</literal> (if <productname>PostgreSQL</productname>
+        was compiled with <option>--with-lz4</option>) or
+        <literal>none</literal> for no compression.
         A compression detail string can optionally be specified.  If the
         detail string is an integer, it specifies the compression level.
         Otherwise, it should be a comma-separated list of items, each of the

src/backend/access/common/toast_compression.c

@@ -23,7 +23,7 @@
 #include "varatt.h"
 
 /* GUC */
-int			default_toast_compression = DEFAULT_TOAST_COMPRESSION;
+int			default_toast_compression = TOAST_PGLZ_COMPRESSION;
 
 #define NO_COMPRESSION_SUPPORT(method) \
 	ereport(ERROR, \

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 => 'DEFAULT_TOAST_COMPRESSION',
+  boot_val => 'TOAST_PGLZ_COMPRESSION',
   options => 'default_toast_compression_options',
 },
 

src/backend/utils/misc/postgresql.conf.sample

@@ -779,7 +779,7 @@
 #row_security = on
 #default_table_access_method = 'heap'
 #default_tablespace = ''                # a tablespace name, '' uses the default
-#default_toast_compression = pglz       # pglz or lz4
+#default_toast_compression = 'pglz'     # 'pglz' or 'lz4'
 #temp_tablespaces = ''                  # a list of tablespace names, '' uses
                                         # only default tablespace
 #check_function_bodies = on

src/bin/initdb/initdb.c

@@ -1426,11 +1426,6 @@ 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.
 	 */

src/include/access/toast_compression.h

@@ -52,15 +52,6 @@ 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 varlena *pglz_compress_datum(const varlena *value);