It is not used (since we dispatch call of sql_bind_*type*() in
sql_bind_column()), so can be removed.

This patch provides straightforward refactoring replacing enum sql_type
with enum mp_type. Note that we use msgpack format instead of field_type
since it is more suitable when dealing with NULLs.

It is obvious that we can't add string with number except the case when
string is a number literal in quotes (aka '123' or '0.5'). Before this
patch values which can't be converted to numbers were just skipped.
Now error is raised. This patch also removes sql_value_numeric_type()
function since it is not used anymore: instead we invoke
mem_apply_numeric_type().

Fix codestyle according to Tarantool guideline; remove unused argument
from signature; make function non-static - we are going to use it in
aggregate function sum() (src/box/sql/func.c) to attempt at converting
string values to numbers.

Redirects can work improperly with libcurl-7.30 and older. CentOS 7
provides libcurl-7.29, so app-tap/http_client.test.lua fails on the
corresponding test case in CI. We need to disable the test case until
#4180 will be resolved.

While we are here fixed httpd.py to write a response at once, not
char-by-char (the typo from daf1ced8). See
gevent/pywsgy.py::process_result().

Related to #4119 and #4180.

While we are here also added forgotten option descriptions to httpc.lua.

@TarantoolBot document
Title: httpc: new 'follow_location' option

When the option is set to `true` (which is default) and a response has
3xx code the http client will automatically issue another request to a
location that a server sends in 'Location' header. If the new response
is 3xx again, the http.client will issue a next request and so on in a
loop until a non-3xx response will be received. This last response will
be returned as a result.

Setting this option to `false` allows to disable this behaviour. In this
case the http client will return a 3xx response itself.

See https://curl.haxx.se/libcurl/c/CURLOPT_FOLLOWLOCATION.html

Previously Tarantool used to raise the confusing error message in
case of invalid usage of the httpc module. Fixed to follow the
current module API.

Closes #4136

The tuple:update() used to work incorrectly in case of empty
tuple produced with box.tuple.new{} because update_create_rope
unconditionally initialized a new rope with [tuple_data,
mp_next(tuple_data)] field that might not exists.

Closes #4041

There was a variable used as a counter from 0 to
uint32_t space_def->field_count. Obviously it can't be < 0, but
there was a check for that. Drop it.

The check was revealed during SQL BOOLEAN review, where one of
patches gets rid of some explicit Expr.type assignments.

According to the ANSI standard, ltrim, rtrim and trim should
be merged into one unified TRIM() function. The specialization of
trimming (left, right or both and trimming characters) determined
in arguments of this function.

Closes #3879

@TarantoolBot document
Title: TRIM() function

Modify signature of SQL function TRIM(). This function removes
characters included in <trim character> (binary) string from
<trim source> (binary) string until encounter a character that doesn't
belong to <trim character>. Removal occurs on the side, specified by
<trim specification>. Now, syntax is following:
TRIM([ [ <trim specification> ] [ <trim character> ] FROM ] <trim source>).

<trim specification> can be one of the following keywords: LEADING,
TRAILING and BOTH.
<trim character> is the set of trimming characters.
<trim source> is the string, that will be trimmed.
If FROM is specified, then:
1) Either <trim specification> or <trim character> or both shall be
specified.
2) If <trim specification> is not specified, then BOTH is implicit.
3) If <trim character> is not specified, then ' ' is implicit.

This patch removes part of unused functions and macros from
main.c. This will facilitate the work of removing SQL error/status
codes.

Needed for #4074

The patch sets format for spaces with sysview engine.
This is done due to following reasons:
  1. Since an SQL view looks into underneath space's format, set
     it for spaces with sysview engine. Before the patch, spaces
     with sysview enginge didn't have its own tuples and hence
     didn't need to have a format.
  2. To use sysview engine to deal with SQL views. This will allow
     to use sysview machinery to query SQL views from Lua land.

Closes #4111

Update_addr and update_payload need to increment member's
incarnation when it is self. For that they used a special
parameter incarnation_inc set in 1 for self and in 0 for others.

It was used to encapsulate incarnation update + event scheduling
on member attribute updates, but on the other hand it broke
another encapsulation level - there should not be exceptions for
'self' in these functions.

This patch makes incarnation increment explicit in the places
where 'self' is updated.

Payload is arbitrary user data disseminated over the cluster
along with other member attributes.

Part of #3234

TTL is time-to-live and it slightly confuses when is said about a
member's attribute. Status_ttl looks like after this value gets
0 the status is deleted or is no longer valid.

TTD is more precise definition for these counters and is expanded
as time-to-disseminate.

Before the patch there were 2 cases when an unchanged packet was
rebuilt partially on each send:

  - cached round message's meta section was rebuilt on each
    EV_WRITE event in swim_scheduler_on_output() function;

  - broadcast message's meta section was rebuilt too even though
    its content does not depend on a broadcast interface.

The third case appears with indirect pings patch which aggravates
meta building business by routing and packet forwarding. When a
packet needs to be forwarded farther, its meta is built in a
special manner preserving the route before EV_WRITE appears, and
on_output should not touch that meta.

This patch adds a check preventing unnecessary meta rebuilds.
Besides, the check and the meta building code are moved into a
dedicated function out of swim_scheduler_on_output() - it allows
to completely split logic of packing a message and sending it.
Separated logic helps a lot when indirect pings are introduced.

Part of #3234

SWIM works in rounds, each split in steps. On step SWIM sends a
round message. The message is not changed between steps of one
round usually, and is cached so as not to rebuild it without
necessity. But when something changes in one member's attributes,
or in the member table, the message is invalidated to be rebuilt
on a next step. Invalidation resets the cached packet.

But it leads to a bug, when a round message is already scheduled
to be sent, however is not actually sent and invalidated in fly.
Such a message on a next EV_WRITE event will be sent as an empty
packet, which obviously makes no sense.

On the other hand it would be harmful to cancel the invalidated
packet if it is in fly, because during frequent changes the
instance will not send anything.

There are no a test case, because empty packets does not break
anything, but still they are useless. And, as it is said above,
such invalidation would prevent sending any round messages when
there are lots of updates.

Follow up for cf0ddeb8
(swim: keep encoded round message cached)

At this moment there are two binary structures in the SWIM
protocol carrying an address: swim_member_passport and
swim_meta_header_bin - one address in each. This code duplication
was not formidable enough to stimulate creation of a separate
address structure.

But forthcoming indirect messages protocol extensions will add 2
new cases of encoding a binary address. It triggered this patch
to reduce code duplication.

Part of #3234

There are several places where it is necessary to check if a
sockaddr_in is nullified, and to compare a couple of addresses.
Some of them are in swim_proto.c, and more are coming in indirect
SWIM messages patch. The patch moves the checkers into
swim_proto.h so as to be usable from anywhere in SWIM.

Also minor renames are made alongside. 'sockaddr_in' is too long
to use in each related function's name, and is replaced with
'inaddr' by analogue with the standard library.

Part of #3234

If a tarantool instance exits while checkpointing is in progress, the
memtx checkpoint thread, which writes the snap file, can access already
freed data resulting in a crash. Let's fix this the same way we did for
relay and vinyl threads - simply cancel the thread forcefully and wait
for it to terminate.

Closes #4170

 - Add REQUESTS.current to report the number of requests currently in
   flight, because it's useful for understanding whether we need to
   increase box.cfg.net_msg_max.
 - Add REQUESTS.{rps,total}, because knowing the number of requests
   processed per second can come in handy for performance analysis.
 - Add CONNECTIONS.{rps,total} that show the number of connections
   opened per second and total. Those are not really necessary, but
   without them the output looks kinda lopsided.

Closes #4150

@TarantoolBot document
Title: Document new box.stat.net fields

Here's the list of the new fields:

 - `CONNECTIONS.rps` - number of connections opened per second recently
   (for the last 5 seconds).
 - `CONNECTIONS.total` - total number of connections opened so far.
 - `REQUESTS.current` - number of requests in flight (this is what's
   limited by `box.cfg.net_msg_max`).
 - `REQUESTS.rps` - number of requests processed per second recently
   (for the last 5 seconds).
 - `REQUESTS.total` - total number of requests processed so far.

`CONNECTIONS.rps`, `CONNECTIONS.total`, `REQUESTS.rps`, `REQUESTS.total`
are reset by `box.stat.reset()`.

Example of the new output:
```
---
- SENT:
    total: 5344924
    rps: 840212
  CONNECTIONS:
    current: 60
    rps: 148
    total: 949
  REQUESTS:
    current: 17
    rps: 1936
    total: 12139
  RECEIVED:
    total: 240882
    rps: 38428
...
```

There can be a lot of small files with vinyl.

increment min range size to 128MB to reduce the amount
of open files per process in a typical install.

Fixes #4165

In contrast to vinyl_iterator, vinyl_index_get doesn't take a reference
to the LSM tree while reading from it. As a result, if the LSM tree is
dropped in the meantime, vinyl_index_get will crash. Fix this issue by
surrounding vy_get with vy_lsm_ref/unref.

Closes #4109

To propagate changes applied to a space while a new index is being
built, we install an on_replace trigger. In case the on_replace
trigger callback fails, we abort the DDL operation.

The problem is the trigger may yield, e.g. to check the unique
constraint of the new index. This opens a time window for the DDL
operation to complete and clear the trigger. If this happens, the
trigger will try to access the outdated build context and crash:

 | #0  0x558f29cdfbc7 in print_backtrace+9
 | #1  0x558f29bd37db in _ZL12sig_fatal_cbiP9siginfo_tPv+1e7
 | #2  0x7fe24e4ab0e0 in __restore_rt+0
 | #3  0x558f29bfe036 in error_unref+1a
 | #4  0x558f29bfe0d1 in diag_clear+27
 | #5  0x558f29bfe133 in diag_move+1c
 | #6  0x558f29c0a4e2 in vy_build_on_replace+236
 | #7  0x558f29cf3554 in trigger_run+7a
 | #8  0x558f29c7b494 in txn_commit_stmt+125
 | #9  0x558f29c7e22c in box_process_rw+ec
 | #10 0x558f29c81743 in box_process1+8b
 | #11 0x558f29c81d5c in box_upsert+c4
 | #12 0x558f29caf110 in lbox_upsert+131
 | #13 0x558f29cfed97 in lj_BC_FUNCC+34
 | #14 0x558f29d104a4 in lua_pcall+34
 | #15 0x558f29cc7b09 in luaT_call+29
 | #16 0x558f29cc1de5 in lua_fiber_run_f+74
 | #17 0x558f29bd30d8 in _ZL16fiber_cxx_invokePFiP13__va_list_tagES0_+1e
 | #18 0x558f29cdca33 in fiber_loop+41
 | #19 0x558f29e4e8cd in coro_init+4c

To fix this issue, let's recall that when a DDL operation completes,
all pending transactions that affect the altered space are aborted by
the space_invalidate callback. So to avoid the crash, we just need to
bail out early from the on_replace trigger callback if we detect that
the current transaction has been aborted.

Closes #4152

We use sizeof as a function in most of the overall code,
fix this nit.

Added a check whether box.cfg() is called within an instance
file. If box.cfg() is missed, point a user the reason of a
fail explicitly.

Before this commit the error was look so:

/usr/bin/tarantoolctl:541: attempt to index a nil value

Closes #3953

In the next patch on payloads it is wanted to drop only packets
containing certain sections such as anti-entropy, dissemination.
New SWIM test transport filters allow to implement this with
ease.

Part of #3234

At this moment SWIM test harness implements its own fake file
descriptor table, which is used unawares by the real SWIM code.
Each fake fd has send and recv queues, can delay and drop
packets with a certain probability. But it is going to be not
enough for new tests.

It is wanted to be able to drop packets with a specified content,
from and to a specified direction. For that the patch implements
a filtering mechanism. Each fake fd now has a list of filters,
applied one by one to each packet. If at least on filter wants to
drop a packet, then it is dropped. The filters know packet
content and direction: outgoing or incomming.

Now only one filter exists - drop rate. It existed even before
the patch, but now it is ported on the new API.

Part of #3234

Move 'update' logic into a separate function, because in the next
commits it is going to become more complicated due to payload
introduction, and it would be undesirable to clog the upsert()
function with payload-specific code.

Part of #3234

Event_bin and member_bin binary packet structures were designed
separately for different purposes. Initially the event_bin was
thought having the same fields as passport + optional old UUID +
optional payload. On the other hand, member_bin was supposed to
store the passport + mandatory payload.

But old UUID was cut off in favour of another way of UUID update.
And payload appeared to be optional in both anti-entropy and
dissemination. It means, that member_bin and event_bin are not
needed anymore as separate structures. This commit replaces them
with the passport completely.

Part of #3234

The new function is swim_decode_bin(), and is going to be used
to safely decode payloads - arbitrary binary data disseminated
alongside with all the other SWIM member attributes.

Part of #3234

Before this commit it always returns false.

Fixes #4091.

Opencoded constants are not good for long time
support, make it named one. Moreover there was
a typo in comment, fid = 0 is reserved as well.

The constant is leftover from 08585902

The test is flaky under high load (e.g. when is run in parallel with a
lot of workers). Make it less dependent on arbitrary timeouts to improve
stability.

Part of #4134

This part of the test is flaky when tests are run in parallel, besides,
it is quite big on its own, so extract it into a separate file to add
more flexibility in running tests and to make finding problems easier.

Part of #4134

Before this patch SQL statement which involves FK constraints creation
or drop didn't increment rowcount:

box.execute("ALTER TABLE t ADD CONSTRAINT fk1 FOREIGN KEY (b) REFERENCES parent (a);")
---
- rowcount: 0
...

This patch fixes this misbehaviour: accidentally VDBE was forgotten to
enable counting changes during ALTER TABLE ADD/DROP constraint.

Closes #4130

When we allocate new fiber we are clearing the whole
structure right after, so no need to call memset again,
coro context is already full of zeros.

Note the coro context is close to 1K size and redundat
memset here is really a penalty.