Allow TestLib::slurp_file to skip contents, and use as needed

In order to avoid getting old logfile contents certain functions in
PostgresNode were doing one of two things. On Windows it rotated the
logfile and restarted the server, while elsewhere it truncated the log
file. Both of these are unnecessary. We borrow from the buildfarm which
does this instead: note the size of the logfile before we start, and
then when fetching the logfile skip to that position before accumulating
contents. This is spelled differently on Windows but the effect is the
same. This is largely centralized in TestLib's slurp_file function,
which has a new optional parameter, the offset to skip to before
starting to reading the file. Code in the client becomes much neater.

Backpatch to all live branches.

Michael Paquier, slightly modified by me.

Discussion: https://postgr.es/m/YHajnhcMAI3++pJL@paquier.xyz

diff --git a/src/test/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index 980f1f15335eae7613759160aa6936b88c859fa6..5b19c23e5055b932df978220bd32fe8c7749cacf 100644 (file)
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -1781,9 +1781,6 @@ sub command_checks_all
 Run a command on the node, then verify that $expected_sql appears in the
 server log file.
 
-Reads the whole log file so be careful when working with large log outputs.
-The log file is truncated prior to running the command, however.
-
 =cut
 
 sub issues_sql_like
@@ -1795,10 +1792,11 @@ sub issues_sql_like
    local $ENV{PGHOST} = $self->host;
    local $ENV{PGPORT} = $self->port;
 
-   truncate $self->logfile, 0;
+   my $log_location = -s $self->logfile;
+
    my $result = TestLib::run_log($cmd);
    ok($result, "@$cmd exit code 0");
-   my $log = TestLib::slurp_file($self->logfile);
+   my $log = TestLib::slurp_file($self->logfile, $log_location);
    like($log, $expected_sql, "$test_name: SQL found in server log");
    return;
 }

diff --git a/src/test/perl/TestLib.pm b/src/test/perl/TestLib.pm
index a7490d2ce7973b145d897ee0793858ffe2c17ec8..fecc6733da66cdfcadaa756b680f008912275bc9 100644 (file)
--- a/src/test/perl/TestLib.pm
+++ b/src/test/perl/TestLib.pm
@@ -46,7 +46,7 @@ use warnings;
 use Config;
 use Cwd;
 use Exporter 'import';
-use Fcntl qw(:mode);
+use Fcntl qw(:mode :seek);
 use File::Basename;
 use File::Find;
 use File::Spec;
@@ -117,7 +117,7 @@ BEGIN
    if ($windows_os)
    {
        require Win32API::File;
-       Win32API::File->import(qw(createFile OsFHandleOpen CloseHandle));
+       Win32API::File->import(qw(createFile OsFHandleOpen CloseHandle setFilePointer));
    }
 
    # Specifies whether to use Unix sockets for test setups.  On
@@ -402,21 +402,27 @@ sub slurp_dir
 
 =pod
 
-=item slurp_file(filename)
+=item slurp_file(filename [, $offset])
 
-Return the full contents of the specified file.
+Return the full contents of the specified file, beginning from an
+offset position if specified.
 
 =cut
 
 sub slurp_file
 {
-   my ($filename) = @_;
+   my ($filename, $offset) = @_;
    local $/;
    my $contents;
    if ($Config{osname} ne 'MSWin32')
    {
        open(my $in, '<', $filename)
          or die "could not read \"$filename\": $!";
+       if (defined($offset))
+       {
+           seek($in, $offset, SEEK_SET)
+             or die "could not seek \"$filename\": $!";
+       }
        $contents = <$in>;
        close $in;
    }
@@ -426,6 +432,11 @@ sub slurp_file
          or die "could not open \"$filename\": $^E";
        OsFHandleOpen(my $fh = IO::Handle->new(), $fHandle, 'r')
          or die "could not read \"$filename\": $^E\n";
+       if (defined($offset))
+       {
+           setFilePointer($fh, $offset, qw(FILE_BEGIN))
+             or die "could not seek \"$filename\": $^E\n";
+       }
        $contents = <$fh>;
        CloseHandle($fHandle)
          or die "could not close \"$filename\": $^E\n";