This commit moves the code in charge of deparsing the method and detail
strings fed later to parse_compress_specification() to a common routine,
where the backward-compatible case of only an integer being found (N
= 0 => "none", N > 1 => gzip at level N) is handled.
Note that this has a side-effect for pg_basebackup, as we now attempt to
detect "server-" and "client-" before checking for the integer-only
pre-14 grammar, where values like server-N and client-N (without the
follow-up detail string) are now valid rather than failing because of an
unsupported method name. Past grammars are still handled the same way,
but these flavors are now authorized, and would now switch to consider N
= 0 as no compression and N > 1 as gzip with the compression level used
as N, with the caller still controlling if the compression method should
be done server-side, client-side or is unspecified. The documentation
of pg_basebackup is updated to reflect that.
This benefits other code paths that would like to rely on the same logic
as pg_basebackup and pg_receivewal with option values used for
compression specifications, one area discussed lately being pg_dump.
Author: Georgios Kokolatos, Michael Paquier
Discussion: https://postgr.es/m/O4mutIrCES8ZhlXJiMvzsivT7ztAMja2lkdL1LJx6O5f22I2W8PBIeLKz7mDLwxHoibcnRAYJXm1pH4tyUNC4a8eDzLn22a6Pb1S74Niexg=@pm.me
Make sure that function declarations use names that exactly match the
corresponding names from function definitions in optimizer, parser,
utility, libpq, and "commands" code, as well as in remaining library
code. Do the same for all code related to frontend programs (with the
exception of pg_dump/pg_dumpall related code).
Like other recent commits that cleaned up function parameter names, this
commit was written with help from clang-tidy. Later commits will handle
ecpg and pg_dump/pg_dumpall.
Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAH2-WznJt9CMM9KJTMjJh_zbL5hD9oX44qdJ4aqZtjFi-zA3Tg@mail.gmail.com
Normally when we use object-oriented programming techniques, we
provide a pointer to an object and then some way of looking up the
associated table of callbacks, but walmethods.c/h took the alternative
approach of providing only a pointer to the table of callbacks and
thus imposed the artificial restriction that there could only ever be
one object of each type, so that the callbacks could find it via a
global variable. That doesn't seem like the right idea, so revise the
approach.
Each callback which does not already have an argument of type
Walfile * now takes a pointer to the relevant WalWriteMethod *
so that these callbacks need not rely on there being only one
object of each type.
Freeing a WalWriteMethod is now performed via a callback provided
for that purpose rather than requiring the caller to know which
WAL method they want to free.
Discussion: http://postgr.es/m/CA+TgmoZS0Kw98fOoAcGz8B9iDhdqB4Be4e=vDZaJZ5A-xMYBqA@mail.gmail.com
Various bits of code were declaring signal handlers manually,
using "int signum" or variants of that. We evidently have no
platforms where that's actually wrong, but let's use our
SIGNAL_ARGS macro everywhere anyway. If nothing else, it's
good for finding signal handlers easily.
No need for back-patch, since this is just cosmetic AFAICS.
Discussion: https://postgr.es/m/2684964.1663167995@sss.pgh.pa.us
In pg_receivewal, compressed output is only flushed on clean exits. The
reason to support SIGTERM as well as SIGINT (which is currently handled)
is that pg_receivewal might well be running as a daemon, and systemd's
default KillSignal is SIGTERM.
Since pg_recvlogical is also supposed to run as a daemon, teach it about
SIGTERM as well and update the documentation to match. While in there,
change pg_receivewal's time_to_stop to be sig_atomic_t like it is in
pg_recvlogical.
Author: Christoph Berg <myon@debian.org>
Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/Yvo/5No5S0c4EFMj@msg.df7cb.de
PG_COMPRESSION_OPTION_LEVEL is removed from the compression
specification logic, and instead the compression level is always
assigned with each library's default if nothing is directly given. This
centralizes the checks on the compression methods supported by a given
build, and always assigns a default compression level when parsing a
compression specification. This results in complaining at an earlier
stage than previously if a build supports a compression method or not,
aka when parsing a specification in the backend or the frontend, and not
when processing it. zstd, lz4 and zlib are able to handle in their
respective routines setting up the compression level the case of a
default value, hence the backend or frontend code (pg_receivewal or
pg_basebackup) has now no need to know what the default compression
level should be if nothing is specified: the logic is now done so as the
specification parsing assigns it. It can also be enforced by passing
down a "level" set to the default value, that the backend will accept
(the replication protocol is for example able to handle a command like
BASE_BACKUP (COMPRESSION_DETAIL 'gzip:level=-1')).
This code simplification fixes an issue with pg_basebackup --gzip
introduced by ffd5365, where the tarball of the streamed WAL segments
would be created as of pg_wal.tar.gz with uncompressed contents, while
the intention is to compress the segments with gzip at a default level.
The origin of the confusion comes from the handling of the default
compression level of gzip (-1 or Z_DEFAULT_COMPRESSION) and the value of
0 was getting assigned, which is what walmethods.c would consider
as equivalent to no compression when streaming WAL segments with its tar
methods. Assigning always the compression level removes the confusion
of some code paths considering a value of 0 set in a specification as
either no compression or a default compression level.
Note that 010_pg_basebackup.pl has to be adjusted to skip a few tests
where the shape of the compression detail string for client and
server-side compression was checked using gzip. This is a result of the
code simplification, as gzip specifications cannot be used if a build
does not support it.
Reported-by: Tom Lane
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/1400032.1662217889@sss.pgh.pa.us
Backpatch-through: 15
This replaces all MemSet() calls with struct initialization where that
is easily and obviously possible. (For example, some cases have to
worry about padding bits, so I left those.)
(The same could be done with appropriate memset() calls, but this
patch is part of an effort to phase out MemSet(), so it doesn't touch
memset() calls.)
Reviewed-by: Ranier Vilela <ranier.vf@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://www.postgresql.org/message-id/9847b13c-b785-f4e2-75c3-12ec77a3b05c@enterprisedb.com
Since babbbb5 and the introduction of LZ4 in pg_receivewal, the
compression of the WAL archived is controlled by two options:
- --compression-method with "gzip", "none" or "lz4" as possible value.
- --compress=N to specify a compression level. This includes a
backward-incompatible change where a value of 0 leads to a failure
instead of no compression enforced.
This commit takes advantage of a4b5754 and 3603f7c to rework the
compression options of pg_receivewal, as of:
- The removal of --compression-method.
- The extenction of --compress to use the same grammar as pg_basebackup,
with a METHOD:DETAIL format, where a METHOD is "gzip", "none" or "lz4"
and a DETAIL is a comma-separated list of options, the only keyword
supported is now "level" to control the compression level. If only an
integer is specified as value of this option, "none" is implied on 0
and "gzip" is implied otherwise. This brings back --compress to be
backward-compatible with ~14, while still supporting LZ4.
This has also the advantage of centralizing the set of checks used by
pg_receivewal to validate its compression options.
Author: Michael Paquier
Reviewed-by: Robert Haas, Georgios Kokolatos
Discussion: https://postgr.es/m/YlPQGNAAa04raObK@paquier.xyz
The same structure, with the same set of elements (for none, lz4, gzip
and zstd), exists in compression.h, so let's make use of the centralized
version instead of duplicating things. Some of the variables used
previously for WalCompressionMethod are renamed to stick better with the
new structure and routine names.
WalCompressionMethod was leading to some confusion in walmethods.c, as
it was sometimes used to refer to some data unrelated to WAL.
Reported-by: Robert Haas
Author: Michael Paquier
Reviewed-by: Robert Haas, Georgios Kokolatos
Discussion: https://postgr.es/m/YlPQGNAAa04raObK@paquier.xyz
Get rid of the separate "FATAL" log level, as it was applied
so inconsistently as to be meaningless. This mostly involves
s/pg_log_fatal/pg_log_error/g.
Create a macro pg_fatal() to handle the common use-case of
pg_log_error() immediately followed by exit(1). Various
modules had already invented either this or equivalent macros;
standardize on pg_fatal() and apply it where possible.
Invent the ability to add "detail" and "hint" messages to a
frontend message, much as we have long had in the backend.
Except where rewording was needed to convert existing coding
to detail/hint style, I have (mostly) resisted the temptation
to change existing message wording.
Patch by me. Design and patch reviewed at various stages by
Robert Haas, Kyotaro Horiguchi, Peter Eisentraut and
Daniel Gustafsson.
Discussion: https://postgr.es/m/1363732.1636496441@sss.pgh.pa.us
lz4frame.h was getting declared after the headers specific to Postgres,
but it needs to be included between postgres_fe.h and the internal
headers.
Issue introduced by babbbb5.
Reported-by: Justin Prysby
Discussion: https://postgr.es/m/20220317111220.GI28503@telsasoft.com
These tests were added recently, but older code tests USE_LZ4 rathr
than HAVE_LIBLZ4, so let's follow the established precedent. It
also seems more consistent with the intent of the configure tests,
since I think that the USE_* symbols are intended to correspond to
what the user requested, and the HAVE_* symbols to what configure
found while probing.
Discussion: http://postgr.es/m/CA+Tgmoap+hTD2-QNPJLH4tffeFE8MX5+xkbFKMU3FKBy=ZSNKA@mail.gmail.com
Both client-side compression and server-side compression are now
supported for zstd. In addition, a backup compressed by the server
using zstd can now be decompressed by the client in order to
accommodate the use of -Fp.
Jeevan Ladhe, with some edits by me.
Discussion: http://postgr.es/m/CA+Tgmobyzfbz=gyze2_LL1ZumZunmaEKbHQxjrFkOR7APZGu-g@mail.gmail.com
Previously it was impossible to terminate these programs via control-C
while they were prompting for a password. We can fix that trivially
for their initial password prompts, by moving setup of the SIGINT
handler from just before to just after their initial GetConnection()
calls.
This fix doesn't permit escaping out of later re-prompts, but those
should be exceedingly rare, since the user's password or the server's
authentication setup would have to have changed meanwhile. We
considered applying a fix similar to commit 46d665bc2, but that
seemed more complicated than it'd be worth. Moreover, this way is
back-patchable, which that wasn't.
The misbehavior exists in all supported versions, so back-patch to all.
Tom Lane and Nathan Bossart
Discussion: https://postgr.es/m/747443.1635536754@sss.pgh.pa.us
pg_receivewal gains a new option, --compression-method=lz4, available
when the code is compiled with --with-lz4. Similarly to gzip, this
gives the possibility to compress archived WAL segments with LZ4. This
option is not compatible with --compress.
The implementation uses LZ4 frames, and is compatible with simple lz4
commands. Like gzip, using --synchronous ensures that any data will be
flushed to disk within the current .partial segment, so as it is
possible to retrieve as much WAL data as possible even from a
non-completed segment (this requires completing the partial file with
zeros up to the WAL segment size supported by the backend after
decompression, but this is the same as gzip).
The calculation of the streaming start LSN is able to transparently find
and check LZ4-compressed segments. Contrary to gzip where the
uncompressed size is directly stored in the object read, the LZ4 chunk
protocol does not store the uncompressed data by default. There is
contentSize that can be used with LZ4 frames by that would not help if
using an archive that includes segments compressed with the defaults of
a "lz4" command, where this is not stored. So, this commit has taken
the most extensible approach by decompressing the already-archived
segment to check its uncompressed size, through a blank output buffer in
chunks of 64kB (no actual performance difference noticed with 8kB, 16kB
or 32kB, and the operation in itself is actually fast).
Tests have been added to verify the creation and correctness of the
generated LZ4 files. The latter is achieved by the use of command
"lz4", if found in the environment.
The tar-based WAL method in walmethods.c, used now only by
pg_basebackup, does not know yet about LZ4. Its code could be extended
for this purpose.
Author: Georgios Kokolatos
Reviewed-by: Michael Paquier, Jian Guo, Magnus Hagander, Dilip Kumar
Discussion: https://postgr.es/m/ZCm1J5vfyQ2E6dYvXz8si39HQ2gwxSZ3IpYaVgYa3lUwY88SLapx9EEnOf5uEwrddhx2twG7zYKjVeuP5MwZXCNPybtsGouDsAD1o2L_I5E=@pm.me
The option name was incorrect in one of the error messages, and the
short option 'I' was used in the code but we did not intend things to be
this way. While on it, fix the documentation to refer to a "method",
and not a "level.
Oversights in commit d62bcc8, that I have detected after more review of
the LZ4 patch for pg_receivewal.
pg_receivewal includes since cada1af the option --compress, to allow the
compression of WAL segments using gzip, with a value of 0 (the default)
meaning that no compression can be used.
This commit introduces a new option, called --compression-method, able
to use as values "none", the default, and "gzip", to make things more
extensible. The case of --compress=0 becomes fuzzy with this option
layer, so we have made the choice to make pg_receivewal return an error
when using "none" and a non-zero compression level, meaning that the
authorized values of --compress are now [1,9] instead of [0,9]. Not
specifying --compress with "gzip" as compression method makes
pg_receivewal use the default of zlib instead (Z_DEFAULT_COMPRESSION).
The code in charge of finding the streaming start LSN when scanning the
existing archives is refactored and made more extensible. While on it,
rename "compression" to "compression_level" in walmethods.c, to reduce
the confusion with the introduction of the compression method, even if
the tar method used by pg_basebackup does not rely on the compression
method (yet, at least), but just on the compression level (this area
could be improved more, actually).
This is in preparation for an upcoming patch that adds LZ4 support to
pg_receivewal.
Author: Georgios Kokolatos
Reviewed-by: Michael Paquier, Jian Guo, Magnus Hagander, Dilip Kumar,
Robert Haas
Discussion: https://postgr.es/m/ZCm1J5vfyQ2E6dYvXz8si39HQ2gwxSZ3IpYaVgYa3lUwY88SLapx9EEnOf5uEwrddhx2twG7zYKjVeuP5MwZXCNPybtsGouDsAD1o2L_I5E=@pm.me
Prior to this patch, when running pg_receivewal, the streaming start
point would be the current location of the archives if anything is
found in the local directory where WAL segments are written, and
pg_receivewal would fall back to the current WAL flush location if there
are no archives, as of the result of an IDENTIFY_SYSTEM command.
If for some reason the WAL files from pg_receivewal were moved, it is
better to try a restart where we left at, which is the replication
slot's restart_lsn instead of skipping right to the current flush
location, to avoid holes in the WAL backed up. This commit changes
pg_receivewal to use the following sequence of methods to determine the
starting streaming LSN:
- Scan the local archives.
- Use the slot's restart_lsn, if supported by the backend and if a slot
is defined.
- Fallback to the current flush LSN as reported by IDENTIFY_SYSTEM.
To keep compatibility with older server versions, we only attempt to use
READ_REPLICATION_SLOT if the backend version is at least 15, and
fallback to the older behavior of streaming from the current flush
LSN if the command is not supported.
Some TAP tests are added to cover this feature.
Author: Ronan Dunklau
Reviewed-by: Kyotaro Horiguchi, Michael Paquier, Bharath Rupireddy
Discussion: https://postgr.es/m/18708360.4lzOvYHigE@aivenronan
The following things are improved:
- Fetch the system identifier from the source server before any
WAL streaming loop. This triggers extra checks to make sure that
pg_receivewal is still connected to a server with the same system ID
with a correct timeline.
- Switch umask() (for file creation mode mask) and RetrieveWalSegSize()
(to fetch the size of WAL segments) a bit later before the initial
stream attempt. If the connection was done with a database,
pg_receivewal would fail but those commands were still executed, which
was a waste. The slot creation and drop are now done before retrieving
the segment size.
Author: Bharath Rupireddy
Reviewed-by: Ronan Dunklau, Michael Paquier
Discussion: https://postgr.es/m/CALj2ACX00YYeyBfoi55Cy=NrP-FcfMgiYYx1qRUEib3yjCVoaA@mail.gmail.com
Most of the integer options for command-line binaries now make use of a
single routine able to do the job, fixing issues with the detection of
sloppy values caused for example by the use of atoi(), that fails on
strings beginning with numerical characters with junk trailing
characters.
This commit cuts down the number of strings requiring translation by 26
per my count, switching the code to have two error types for invalid and
out-of-range values instead.
Much more could be done here, with float or even int64 options, but
int32 was the most appealing case as it is possible to rely on strtol()
to do the job reliably. Note that there are some exceptions for now,
like pg_ctl or pg_upgrade that use their own logging logic. A couple of
negative TAP tests required some adjustments for the new errors
generated.
pg_dump and pg_restore tracked the maximum number of parallel jobs
within the option parsing. The code is refactored a bit to track that
in the code dedicated to parallelism instead.
Author: Kyotaro Horiguchi, Michael Paquier
Reviewed-by: David Rowley, Álvaro Herrera
Discussion: https://postgr.es/m/CALj2ACXqdG9WhqVoJ9zYf-iZt7sgK7Szv5USs=he6NnWQ2ofTA@mail.gmail.com
Extend the replication command CREATE_REPLICATION_SLOT to support the
TWO_PHASE option. This will allow decoding commands like PREPARE
TRANSACTION, COMMIT PREPARED and ROLLBACK PREPARED for slots created with
this option. The decoding of the transaction happens at prepare command.
This patch also adds support of two-phase in pg_recvlogical via a new
option --two-phase.
This option will also be used by future patches that allow streaming of
transactions at prepare time for built-in logical replication. With this,
the out-of-core logical replication solutions can enable replication of
two-phase transactions via replication protocol.
Author: Ajin Cherian
Reviewed-By: Jeff Davis, Vignesh C, Amit Kapila
Discussion:
https://postgr.es/m/02DA5F5E-CECE-4D9C-8B4B-418077E2C010@postgrespro.ruhttps://postgr.es/m/64b9f783c6e125f18f88fbc0c0234e34e71d8639.camel@j-davis.com
Existing code used various inconsistent ways to printf struct stat's
st_size member. The type of that is off_t, which is in most cases a
signed 64-bit integer, so use the long long int format for it.
This is still using the 2.0 version of pg_bsd_indent.
I thought it would be good to commit this separately,
so as to document the differences between 2.0 and 2.1 behavior.
Discussion: https://postgr.es/m/16296.1558103386@sss.pgh.pa.us
The original placement of this module in src/fe_utils/ is ill-considered,
because several src/common/ modules have dependencies on it, meaning that
libpgcommon and libpgfeutils now have mutual dependencies. That makes it
pointless to have distinct libraries at all. The intended design is that
libpgcommon is lower-level than libpgfeutils, so only dependencies from
the latter to the former are acceptable.
We already have the precedent that fe_memutils and a couple of other
modules in src/common/ are frontend-only, so it's not stretching anything
out of whack to treat logging.c as a frontend-only module in src/common/.
To the extent that such modules help provide a common frontend/backend
environment for the rest of common/ to use, it's a reasonable design.
(logging.c does not yet provide an ereport() emulation, but one can
dream.)
Hence, move these files over, and revert basically all of the build-system
changes made by commit cc8d41511. There are no places that need to grow
new dependencies on libpgcommon, further reinforcing the idea that this
is the right solution.
Discussion: https://postgr.es/m/a912ffff-f6e4-778a-c86a-cf5c47a12933@2ndquadrant.com
This unifies the various ad hoc logging (message printing, error
printing) systems used throughout the command-line programs.
Features:
- Program name is automatically prefixed.
- Message string does not end with newline. This removes a common
source of inconsistencies and omissions.
- Additionally, a final newline is automatically stripped, simplifying
use of PQerrorMessage() etc., another common source of mistakes.
- I converted error message strings to use %m where possible.
- As a result of the above several points, more translatable message
strings can be shared between different components and between
frontends and backend, without gratuitous punctuation or whitespace
differences.
- There is support for setting a "log level". This is not meant to be
user-facing, but can be used internally to implement debug or
verbose modes.
- Lazy argument evaluation, so no significant overhead if logging at
some level is disabled.
- Some color in the messages, similar to gcc and clang. Set
PG_COLOR=auto to try it out. Some colors are predefined, but can be
customized by setting PG_COLORS.
- Common files (common/, fe_utils/, etc.) can handle logging much more
simply by just using one API without worrying too much about the
context of the calling program, requiring callbacks, or having to
pass "progname" around everywhere.
- Some programs called setvbuf() to make sure that stderr is
unbuffered, even on Windows. But not all programs did that. This
is now done centrally.
Soft goals:
- Reduces vertical space use and visual complexity of error reporting
in the source code.
- Encourages more deliberate classification of messages. For example,
in some cases it wasn't clear without analyzing the surrounding code
whether a message was meant as an error or just an info.
- Concepts and terms are vaguely aligned with popular logging
frameworks such as log4j and Python logging.
This is all just about printing stuff out. Nothing affects program
flow (e.g., fatal exits). The uses are just too varied to do that.
Some existing code had wrappers that do some kind of print-and-exit,
and I adapted those.
I tried to keep the output mostly the same, but there is a lot of
historical baggage to unwind and special cases to consider, and I
might not always have succeeded. One significant change is that
pg_rewind used to write all error messages to stdout. That is now
changed to stderr.
Reviewed-by: Donald Dong <xdong@csumb.edu>
Reviewed-by: Arthur Zakirov <a.zakirov@postgrespro.ru>
Discussion: https://www.postgresql.org/message-id/flat/6a609b43-4f57-7348-6480-bd022f924310@2ndquadrant.com
Commit c0d0e54084 replaced the ones in the documentation, but missed out
on the ones in the code. Replace those as well, but unlike c0d0e54084,
don't backpatch the code changes to avoid breaking translations.
PostgreSQL uses a custom wrapper for open() and fopen() which is
concurrent-safe, allowing multiple processes to open and work on the
same file. This has a couple of advantages:
- pg_test_fsync does not handle O_DSYNC correctly otherwise, leading to
false claims that disks are unsafe.
- TAP tests can run into race conditions when a postmaster and pg_ctl
open postmaster.pid, fixing some random failures in the buildfam.
pg_upgrade is one frontend tool using workarounds to bypass file locking
issues with the log files it generates, however the interactions with
pg_ctl are proving to be tedious to get rid of, so this is left for
later.
Author: Laurenz Albe
Reviewed-by: Michael Paquier, Kuntal Ghosh
Discussion: https://postgr.es/m/1527846213.2475.31.camel@cybertec.at
Discussion: https://postgr.es/m/16922.1520722108@sss.pgh.pa.us
Some error messages related to file handling are using the code path
context to define their state. For example, 2PC-related errors are
referring to "two-phase status files", or "relation mapping file" is
used for catalog-to-filenode mapping, however those prove to be
difficult to translate, and are not more helpful than just referring to
the path of the file being worked on. So simplify all those error
messages by just referring to files with their path used. In some
cases, like the manipulation of WAL segments, the context is actually
helpful so those are kept.
Calls to the system function read() have also been rather inconsistent
with their error handling sometimes not reporting the number of bytes
read, and some other code paths trying to use an errno which has not
been set. The in-core functions are using a more consistent pattern
with this patch, which checks for both errno if set or if an
inconsistent read is happening.
So as to care about pluralization when reading an unexpected number of
byte(s), "could not read: read %d of %zu" is used as error message, with
%d field being the output result of read() and %zu the expected size.
This simplifies the work of translators with less variations of the same
message.
Author: Michael Paquier
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/20180520000522.GB1603@paquier.xyz
Allow the cluster to be optionally init'd with read access for the
group.
This means a relatively non-privileged user can perform a backup of the
cluster without requiring write privileges, which enhances security.
The mode of PGDATA is used to determine whether group permissions are
enabled for directory and file creates. This method was chosen as it's
simple and works well for the various utilities that write into PGDATA.
Changing the mode of PGDATA manually will not automatically change the
mode of all the files contained therein. If the user would like to
enable group access on an existing cluster then changing the mode of all
the existing files will be required. Note that pg_upgrade will
automatically change the mode of all migrated files if the new cluster
is init'd with the -g option.
Tests are included for the backend and all the utilities which operate
on the PG data directory to ensure that the correct mode is set based on
the data directory permissions.
Author: David Steele <david@pgmasters.net>
Reviewed-By: Michael Paquier, with discussion amongst many others.
Discussion: https://postgr.es/m/ad346fe6-b23e-59f1-ecb7-0e08390ad629%40pgmasters.net
When requesting a particular replication slot, the new pg_basebackup
option -C/--create-slot creates it before starting to replicate from it.
Further refactor the slot creation logic to include the temporary slot
creation logic into the same function. Add new arguments is_temporary
and preserve_wal to CreateReplicationSlot(). Print in --verbose mode
that a slot has been created.
Author: Michael Banck <michael.banck@credativ.de>