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/[email protected]

diff --git a/src/test/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index 98fddbf9cd39145f6e26f74fc766be29b63a4064..f2381c0c361048a3e12376d6195e59288d29965b 100644 (file)
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -1673,9 +1673,6 @@ 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
@@ -1687,10 +1684,11 @@ 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 4cb3c765d939e55a58e3ab0613c4f4df8b9e3db4..63975db5e76cc8d5c1ca86201ace571095110923 100644 (file)
--- a/src/test/perl/TestLib.pm
+++ b/src/test/perl/TestLib.pm
@@ -13,7 +13,7 @@ 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;
@@ -82,7 +82,7 @@ BEGIN
    if ($windows_os)
    {
        require Win32API::File;
-       Win32API::File->import(qw(createFile OsFHandleOpen CloseHandle));
+       Win32API::File->import(qw(createFile OsFHandleOpen CloseHandle setFilePointer));
    }
 }
 
@@ -259,13 +259,18 @@ sub slurp_dir
 
 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 $in;
    }
@@ -275,6 +280,11 @@ sub slurp_file
          or die "could not open \"$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";