Previously "BEGIN" / "BEGIN TRANSACTION", "COMMIT TRANSACTION" /
"END" / "END TRANSACTION", "ROLLBACK TRANSACTION" could be used
to handle transactions. By changing these commands syntax in
parser we're aiming on getting closer to ANSI SQL. Also found
initialization in ifdef that caused some problems with error
messages in occasions when the wrong syntax was used.

With the patch applied only following commands can be used:
 - "START TRANSACTION" to begin transaction.
 - "COMMIT" to end transaction.
 - "ROLLBACK" to rollback transaction without savepoints.
 - "ROLLBACK TO .." to rollback transaction to savepoint.

Closes #2164

To optimize the select-subquery tarantool uses
subquery flattening optimization which is only used
with respect to some restrictions. When any of
subselects but the last one has an ORDER BY
clause we should raise an error. So subquery
components containing it are not accepted
to be optimized.

Checking part was only checking if the last
subselect contains the clause which led to an
assertion fail. With the patch applied
flattening is not used in case any of
subselects has an ORDER BY.

Closes #3353

_say function was called with invalid arguments.
Thank @sorc1 for patch.

Closes #3433.

Strdup may silently fail without any message from tarantool.
Patch adds this checks.

Mode logging to syslog was broken due to assertion in case
ov vaild configuration:

  box.cfg{log = 'syslog:identity=tarantool'}

Closes #3502

Strings containing "true" and "false" were converted
to a boolean type when serializing. Fixed.
Example:
type(yaml.decode(yaml.encode('false'))) == string
type(yaml.decode(yaml.encode('true'))) == string

Closes #3476.

Function tonumber64 has worked incorrectly with values less
than INT64_MAX.
Now it works in the interval [INT64_MAX, UINT64_MAX] returning
nil otherwise.

Closes #3466.

Net.box didn't pass options containing iterator to
server side.
There were also invalid results for two :count tests in
net.box.result file.

Thanks @ademenev for contributing problem and help with
problem locating.

Closes #3262.

Parser didn't raise error when DELETE FROM can't find
a table specified on statement.
As no error was raised, partially-prepared VDBE code
seemed to be generated fine, that was not true.

Closes #3535, #3511.

Before the patch, big integer constants were silently
converted to floating point values. Fix that by issuing
error message if value doesn't fit in int64_t range.

Also, refactor surrounding code as per Tarantool's code style.

Closes #2347

Currently, this function takes a single boolean argument, but I'm
planning to add another one. Since two bool arguments look rather
confusing, let's turn this arguments into flags.

Needed for #461

A small cleanup to avoid a potentially inefficient use of
gc_consumer_vclock().

Follow up on a patch for gh-461.

In order to check if a replica needs to be rebootstrapped, we need to
know the vclock of the oldest WAL stored on the master, but the garbage
collector works with signatures and hence can't report the vclock it was
last called for. Actually, all gc users have a vclock and can pass it
instead of signature so it's pretty easy to switch garbage collection
infrastructure to vclock.

Needed for #461

We will need it in other places.

 - Remove extra scan of the WAL directory from local_recovery() - we
   scan the directory in recovery_end_vclock() hence we can skip scan in
   recover_remaining_wals() by passing scan_dir = false.

 - Rename recovery_end_vclock() to recovery_scan() to emphasize the fact
   that this function scans the WAL directory. Write a comment to this
   function.

 - Add comments to wal.c explaining why we scan the WAL directory there.

Follow-up 0695fbbb ("box: retrieve end vclock before starting local
recovery").

To bring crash_expected option of "start server" command.

There were no checks for granting and revoking a non-existent
privilege or a privilege to a non-existent entity.
Added the checks, and a test case.

Closes #3417

Net.box didn't pass options containing iterator to
server side.
There were also invalid results for two :count tests in
net.box.result file.

Thanks @ademenev for contributing problem and help with
problem locating.

Closes #3262.

Now every sqlite struct Index is created with tnt
struct index_def inside. This allows us to use tnt
index_def in work with sqlite indexes in the same
manner as with tnt index and is a step to remove
sqlite Index with tnt index.
Fields coll_array, coll_id_array, aiColumn,
sort_order, aiRowLogEst and zName are removed from
Index. All usages of this fields changed to usage of
corresponding index_def or index_def->opts fields.
index_is_unique(), sql_index_collation() and
index_column_count() are removed with calls of
index_def corresponding fields.
Also there is small change in behavior: before the
patch a statement like
CREATE TABLE t1(a,b, PRIMARY KEY(a,b), UNIQUE(a,b))
created only one constraint index (for primary key)
and no index for UNIQUE constraint (since it is upon
the same columns), neither it is named or non-named
constraint.
After the patch index will be always created for named
constraints. It is a temporary solution. In future
it's preferable not to create an index, but to make
some record in _constraints space that this named
unique constraint implemented with the same index as
primary key constraint.

Closes: #3369, #3498

Binary search in whereKeyStats function that uses routine
sqlite3VdbeRecordCompareMsgpack returned invalid result,
because it made wrong assumption about the number of
coinciding index columns based on _sql_stat4.
But all collected index statistics were wrong.

The analyzeOneTable routine used to call sqlite3GetTempRange
and sqlite3ReleaseTempRange functions inside of cycle intensively
changes Parser->nMem value. Thanks this pattern routine
sqlite3ReleaseTempRange could push nMem variable onto aTempReg
queue. As Parser->nMem could be bigger next time, this
variable may be used twice:

          [74, 'Column', 4, 1, 11, '', '00', 'r[11]=']
          [75, 'Column', 4, 2, 12, '', '00', 'r[12]=']
|->       [76, 'Column', 4, 3, 13, '', '00', 'r[13]=']
          [77, 'Column', 4, 4, 14, '', '00', 'r[14]=']
!rewrite  [78, 'Column', 4, 0, 13, '', '00', 'r[13]=ID']
          [79, 'MakeRecord', 13, 1, 6, '', '00',
           'r[6]=mkrec(r[13])']

Thus all assumptions about data below should be invalid and
some artifacts could exhibit.

Example:
\set language sql
CREATE TABLE t1(id INTEGER PRIMARY KEY AUTOINCREMENT, a,
		b, c, f, d, e);
CREATE INDEX i1 ON t1(a, b, c, f, d);
\set language lua
for i = 0, 100 do
    box.sql.execute(string.format("INSERT INTO t1 VALUES(null,
		    'x', 'y', 'z', 'a', %s, %s);", i,
		    math.floor(i / 2)))
end
\set language sql
SELECT * FROM "_sql_stat4";
---
['T1', 'I1', '101 101 1 1 1', '0 0 44 44 44', '0 0 44 44 44',
 ['x', 'y', 'z', 'a', 44]]
---

Expected:
---
['T1', 'I1', '101 101 101 101 1', '0 0 0 0 44', '0 0 0 0 44',
 ['x', 'y', 'z', 'a', 44]]
---

Resolves #2847.

If is_first_insert flag is set and vy_stmt_type(rv->tuple) equals
IPROTO_DELETE, we free rv->tuple, but then we dereference it via
an on-stack variable to check if we need to turn a REPLACE into an
INSERT or vice versa. Fix this.

This is not necessary, as we can use fiber()->gc, as we usually do.

Move key_def creation to compare_write_iterator_results as it is the
same for all test cases. Performance is not an issue here, obviously, so
we can close our eyes to the fact that now we create a new key def for
each test cases.

The new function inserts a new item into the list at the specified
postion.

If a fiber pool reuses already canceled fiber then the fiber reports an
error for any next request. Now canceled fiber returns and fiber pool
creates a new one.

Fixes #3527

Disallowed division by zero in SQL to follow ANSI standard.
This also affects some unobvious scenarios when divider indirectly
casts to zero like
SELECT 'word1' / 'word2';

Closes #2135.

New commit in third_party/libyaml downgrades
required cmake version.

If specified PK column modifier refers nonexistent column,
lookup by name keeps NULL column pointer unchanged that should
be accounted in assert.

Close #3522.

Closes #2946.

@TarantoolBot document
Title: fixed module reload
There was a bug in tarantool documentation:
https://tarantool.io/en/doc/1.7/book/box/
box_schema/#lua-function.box.schema.func.reload
Now it is allowed to reload all functions in loadable
module via one method. Legacy method including finction
name is forbidden.
box.schema.func.reload("utils")       -- ok since now
box.schema.func.reload("utils.func1") -- forbidden since now

Global reload is still unsupported because it seems
to be useless.
box.schema.func.reload()              -- invalid!