Bloom filter depends on hash function, which depends on ICU
version, which may vary.

+ Don't use id=0 for collations

Follow up #2649

Fix tuple_hash_field() to handle the following cases properly:

 - Nullable string field (crash in vinyl on dump).
 - Scalar field with collation enabled (crash in memtx hash index).

Add corresponding test cases.

First, unique but nullable indexes are not rebuilt when the primary key
is altered although they should be, because they can contain multiple
NULLs. Second, when rebuilding such indexes we use a wrong key def
(index_def->key_def instead of cmp_def), which results in lost stable
order after recovery. Fix both these issues and add a test case.

Needed to check if the key definition loaded from vylog to send initial
data to a replica has the collation properly recovered.

It isn't stored currently, but this doesn't break anything, because the
primary key, which is the only key whose definition is used after having
been loaded from vylog, can't be nullable. Let's store it there just in
case. Update the vinyl/layout test to check that.

Collations were disabled in vinyl by commmit 2097908f ("Fix
collation test on some platforms and disable collation in vinyl"),
because a key_def referencing a collation could not be loaded from
vylog on recovery (collation objects are created after vylog is
recovered). Now, it isn't a problem anymore, because the decoding
procedure, key_def_decode_parts(), deals with struct key_part_def,
which references a collation by id and hence doesn't need a collation
object to be created. So we can enable collations in vinyl.

This patch partially reverts the aforementioned commit (it can't
do full revert, because that commit also fixed some tests along
the way).

Closes #2822

The corresponding comparator is missing, which leads to a crash.
Fix it and add a test case checking that nullable indexes work fine
with all available types.

Symbol resolving can be expensive. Introduce an option for fiber.info():

    fiber.info({ backtrace = true })
    fiber.info({ bt = true })

Fixes #2878

- Change signature of function access_check_func.
  Now it returns status instead of function.

Close #2816

 - Remove vy_stat::rmean statistics, which were left from Sophia, as now
   we have per index statistics which are much more verbose than those.

 - Move vy_stat::dump_bw to vy_env and remove struct vy_stat as there's
   nothing left in it.

 - Move quota statistics from box.info.vinyl().performance.memory to
   box.info.vinyl().quota. Remove 'ratio', which equals used / limit, as
   this kind of calculations should be done by a script aggregating
   statistics. Report 'use_rate' and 'dump_bandwidth' there.

 - Report 'limit' in cache statistics to make them consistent with
   'quota' statistics, where 'limit' is reported. Rename 'cache.count'
   to 'cache.tuples'. Remove vy_cache_env::cache_count, use mempool
   stats instead.

 - Move 'tx_allocated', 'txv_allocated', 'read_interval', 'read_view'
   from box.info.vinyl().performance to box.info.vinyl().tx and name
   them 'transactions', 'statements', 'gap_locks', and 'read_views',
   respectively. Remove vy_tx_stat::active and 'tx.active' as the same
   value is shown by 'tx.transactions', extracted from the mempool.

 - Zap box.info.vinyl().performance - there's nothing left there.

Now global statistics look like:

  tarantool> box.info.vinyl()
  ---
  - cache:
      limit: 134217728
      tuples: 32344
      used: 34898794
    tx:
      conflict: 1
      commit: 324
      rollback: 13
      statements: 10
      transactions: 3
      gap_locks: 4
      read_views: 1
    quota:
      dump_bandwidth: 10000000
      watermark: 119488351
      use_rate: 1232703
      limit: 134217728
      used: 34014634
  ...

Closes #2861

Follow up #1557

Collation was simply ignored for non-string parts, that could
confuse potential user.

Generate a readable error in this case.

Fix #2862 part 2

Now collation is silently ignored for type='scalar' parts.

Use collation for string scalar fields.

Fix #2862 part 1

Show collation name (if present) in space.index.name.parts[no].

Fix #2862 part 4

test:create_index('unicode_s1', {parts = {{1, 'STR', collation =
'UNICODE'}}}) will work now.

Fix #2862 part 3

If a field is not indexed and no more indexed or not nullable
fields after that, than allow to skip it in insertion. Such field
value looks like MP_NIL, but MP_NIL is not explicitly stored.
Named access to this field in lua returns nil.

Example:
format =
{{'field1'},
 {'field2'},
 {'field3', is_nullable = true},
 {'field4', is_nullable = true}}

t = space:insert{1, 2} -- ok.

t.field1 == 1, t.field2 == 2, t.field3 == nil, t.field4 == nil

Closes #2880

Some users store in format fields their custom keys. But current
opts parser does not allow to store any unknown keys. Lets allow it.

Example:
format = {}
format[1] = {name = 'field1', type = 'unsigned', custom_field = 'custom_value'}
s = box.schema.create_space('test', {format = format})
s:format()[1].custom_field == 'custom_value'

Closes #2839

Using DML/DDL on a Vinyl index with wal_mode = 'none' is likely to
result in unrecoverable errors like:

  F> can't initialize storage: Invalid VYLOG file: Index 512/0 created twice

To avoid data corruption in case the user tries to use an existing Vinyl
database in conjunction with wal_mode = 'none', let's explicitly forbid
it until we figure out how to fix it.

Workaround #2278

During initial join, a replica receives all data accumulated on the
master for its whole lifetime, which may be quota a lot. If the network
connection is fast enough, the replica might fail to keep up with dumps,
in which case replication fails with ER_VY_QUOTA_TIMEOUT. To avoid that,
let's ignore quota timeout until bootstrap is complete.

Note, replication may still fail during the 'subscribe' stage for the
same reason, but it's unlikely, because the rate at which the master
sends data is limited by the number of requests served by the master per
a unit of time, and it should become nearly impossible once throttling
is introduced (See #1862).

Closes #2873

If the user sets snap_dir to an empty directory by mistake while leaving
vinyl_dir the same, tarantool will still bootstrap, but there is likely
to be errors like:

  vinyl.c:835 E> 512/0: dump failed: file './512/0/00000000000000000001.run' already exists
  vy_log.c:1095 E> failed to rotate metadata log: file './00000000000000000005.vylog' already exists

Even worse, it may eventually fail to restart with:

  vy_log.c:886 E> ER_MISSING_SNAPSHOT: Can't find snapshot

To avoid that, let's check the vinyl_dir on bootstrap and abort if it
contains vylog files left from previous setups.

Closes #2872

If xlog_flush() fails, box.snapshot() will still succeed, but
recovery from such an incomplete snapshot will fail. Fix it and
add the corresponding test case.

Update netbox.space objects in-place instead of re-creating them
on every schema change.

Closes #2401

* Add support of string.strip, string.lstrip, string.rstrip

Closes #2785

This reverts commit 8b6cefd0.

This feature is so good to be pushed into 1.7. Sorry.

Fixes #2852.
Fixes #2849.

Tomap() creates a lua table with both names and number indexes.
Each named field stored by its name AND by its index in a tuple.
For example, if a tuple is {'a', 'b', 'c'} and its format is
{'field1', 'field2'}, then t.field1 is the same as t[1], t.field2 is
the same as t[2].

Not named fields can be accessed only by their indexes. For the example
above 'c' can be accessed only as t[3].

Closes #2821

* Call box.cfg() instead of raising an error on the first access to box.XXX

Fixes #2559

Fix typos in types check in string module

Closes #2775

Check request fields on NULL before print.

Needed to remove monitoring fibers from shard and use only netbox
api to track, if a connection is closed or reopened.

Closes #2858

Closes #2779

> src/box/txn.c:454:40: error: '_Alignof' applied to an expression is a GNU extension [-Werror,-Wgnu-alignof-expression]
>                 diag_set(OutOfMemory, sizeof(*svp) + alignof(*svp) - 1,
>                                                      ^

Do not try to be smart and guess allocation size using alignof.

> src/box/memtx_tree.c:391:11: error: comparison of unsigned enum expression < 0 is always false [-Werror,-Wtautological-compare]
>         if (type < 0 || type > ITER_GT) { /* Unsupported type */
>             ~~~~ ^ ~

> src/box/vinyl_index.c:184:29: error: comparison of unsigned enum expression < 0 is always false [-Werror,-Wtautological-compare]
>         if (type > ITER_GT || type < 0) {
>                               ~~~~ ^ ~

Move the check for illegal params (i.e. 'type < 0') to the box API.
In index callbacks, only check that the iterator type is supported
by the index.

The primary reason for these methods to be implemented differently
for memtx and vinyl was the 'position' optimization exploited by
the memtx engine: since selects from memtx do not yield, we could
use a preallocated iterator there.

Now, as the 'position' optimization became redundant and was
removed due to the switch to memory pools for iterator allocations,
the only idiosyncrasy left in the memtx implementation is the count()
optimization: count() falls back on size() for ITER_ALL. Since this
optimization consists of just a few lines of code, we don't really
need memtx_index_count() co-used by all memtx index implementations:
we can implement it in each memtx index separately.

That being said, let us:
 - implement generic versions of min(), max(), and count();
 - make vinyl, memtx, and sysview engines use generic versions of
   the above-mentioned methods if appropriate;
 - Remove memtx_index.[hc]

As a side-effect, this patch enables min(), max(), and count() in
the sysview engine, but that is not bad considering that this engine
implements general-purpose iterator for its indexes.

Fixes #2845

Closes #2832

Closes #2773

After implementing of #2802 many user started to complain about
sudden change of _index system space format.

Since both formats (new and old) are fully supported it is possible
to store part definition in old format if there are no collation or
other special options. Make it.

Closes #2802