Set minimum required version of zstd as 1.4.0.

It emerges that our new zstd code depends on features that were not
present (or at least not enabled by default) in zstd before 1.4.0.
That's already four years old, so there's little reason to try to
make our code work with something older.  Instead make configure
check that zstd is at least 1.4.0, and document this requirement.

Justin Pryzby (doc changes by me)

Discussion: https://postgr.es/m/efbd94cd1102f99fd1300e44905ee4a994ee2ef6.camel@gunduz.org

configure

@@ -9092,19 +9092,19 @@ $as_echo "$with_zstd" >&6; }
 if test "$with_zstd" = yes; then
 
 pkg_failed=no
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd" >&5
-$as_echo_n "checking for libzstd... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libzstd >= 1.4.0" >&5
+$as_echo_n "checking for libzstd >= 1.4.0... " >&6; }
 
 if test -n "$ZSTD_CFLAGS"; then
     pkg_cv_ZSTD_CFLAGS="$ZSTD_CFLAGS"
  elif test -n "$PKG_CONFIG"; then
     if test -n "$PKG_CONFIG" && \
-    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd >= 1.4.0\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd >= 1.4.0") 2>&5
   ac_status=$?
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
-  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd" 2>/dev/null`
+  pkg_cv_ZSTD_CFLAGS=`$PKG_CONFIG --cflags "libzstd >= 1.4.0" 2>/dev/null`
 		      test "x$?" != "x0" && pkg_failed=yes
 else
   pkg_failed=yes
@@ -9116,12 +9116,12 @@ if test -n "$ZSTD_LIBS"; then
     pkg_cv_ZSTD_LIBS="$ZSTD_LIBS"
  elif test -n "$PKG_CONFIG"; then
     if test -n "$PKG_CONFIG" && \
-    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "libzstd") 2>&5
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libzstd >= 1.4.0\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libzstd >= 1.4.0") 2>&5
   ac_status=$?
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
-  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd" 2>/dev/null`
+  pkg_cv_ZSTD_LIBS=`$PKG_CONFIG --libs "libzstd >= 1.4.0" 2>/dev/null`
 		      test "x$?" != "x0" && pkg_failed=yes
 else
   pkg_failed=yes
@@ -9142,14 +9142,14 @@ else
         _pkg_short_errors_supported=no
 fi
         if test $_pkg_short_errors_supported = yes; then
-	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd" 2>&1`
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libzstd >= 1.4.0" 2>&1`
         else
-	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd" 2>&1`
+	        ZSTD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libzstd >= 1.4.0" 2>&1`
         fi
 	# Put the nasty error message in config.log where it belongs
 	echo "$ZSTD_PKG_ERRORS" >&5
 
-	as_fn_error $? "Package requirements (libzstd) were not met:
+	as_fn_error $? "Package requirements (libzstd >= 1.4.0) were not met:
 
 $ZSTD_PKG_ERRORS
 

configure.ac

@@ -1073,7 +1073,7 @@ AC_MSG_RESULT([$with_zstd])
 AC_SUBST(with_zstd)
 
 if test "$with_zstd" = yes; then
-  PKG_CHECK_MODULES(ZSTD, libzstd)
+  PKG_CHECK_MODULES(ZSTD, libzstd >= 1.4.0)
   # We only care about -I, -D, and -L switches;
   # note that -lzstd will be added by AC_CHECK_LIB below.
   for pgac_option in $ZSTD_CFLAGS; do

doc/src/sgml/installation.sgml

@@ -250,7 +250,7 @@ su - postgres
       encrypted client connections.  <productname>OpenSSL</productname> is
       also required for random number generation on platforms that do not
       have <filename>/dev/urandom</filename> (except Windows).  The minimum
-      version required is 1.0.1.
+      required version is 1.0.1.
      </para>
     </listitem>
 
@@ -265,7 +265,7 @@ su - postgres
     <listitem>
      <para>
       You need <productname>LZ4</productname>, if you want to support
-      compression of data with this method; see
+      compression of data with that method; see
       <xref linkend="guc-default-toast-compression"/> and
       <xref linkend="guc-wal-compression"/>.
      </para>
@@ -274,8 +274,9 @@ su - postgres
     <listitem>
      <para>
       You need <productname>zstd</productname>, if you want to support
-      compression of data with this method; see
+      compression of data with that method; see
       <xref linkend="guc-wal-compression"/>.
+      The minimum required version is 1.4.0.
      </para>
     </listitem>