Currently, the rc field of the VDBE structure is either 0 or -1.
Due to this, it is better to replace this integer field with the
boolean field is_aborted.

This field has become unused and should be removed.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error code is part of getting rid of the SQL error
system.

Removing this error/status code is part of getting rid of the SQL
error system.

Removing this error code is part of getting rid of the SQL error
system.

Removing these error codes is part of getting rid of the SQL error
system.

Removing this error/status code is part of getting rid of the SQL
error system.

Since the lookaside system is not currently in use, it must be
completely removed.

These functions are not currently used and should be removed.

These functions are part of the SQL error system, which is
replaced by the Tarantool error system. They are not needed now,
so they will be deleted.

This field has become unused and should be removed.

This field has become unused and should be removed.

This field has become unused and should be removed.

Get rid of duplicated fiber on stop logic.

Prerequisites: #1254

To apply replicated rows in parallel, we need to be able to complete
transactions asynchronously, from the tx_prio callback. We can't yield
there so we must ensure that on_commit/on_rollback triggers don't yield.
The only place where we may yield in a completion trigger is vinyl DDL,
which submits vylog records and waits for them to complete.

Actually, there's no reason to wait for vylog write to complete, as we
can handle missing records on recovery. So this patch reworks vylog to
make vy_log_tx_try_commit() and hence on_commit/on_rollback triggers
using it non-yielding.

To achieve that, we need to:

 - Use vy_log.latch only to sync log rotation vs writes. Don't protect
   vylog buffer with it. This makes vy_log_tx_begin() non-yielding.

 - Use a separate list and buffer for storing vylog records of each
   transaction. We used to share them among transactions, but without
   vy_log.latch we can't sync access to them anymore. Since vylog
   transactions are rare events, this should be fine.

 - Make vy_log_tx_try_commit() append the transaction to the list of
   pending transactions and wake up a background fiber to flush all
   pending transactions. This way it doesn't need to yield.

Closes #4218

Receive function behaved inconsistently for the cases where
first we use an integer as a pattern as to tell the function
a specific number of elements we want to read, and then
perform another receive call using '*a' as a pattern.
The latter should have denoted that we want to get all there
is to get, but instead it was possible to get only a part of
data and also in non-sequential order.

Closes #4118

URI reconfiguration causes incarnation increment in order to
forcefully rewrite old value on remote instances. But that update
was not delivered to a user via triggers. The patch fixes that.

vy_tx_handle_deferred_delete() expects (righteously) that in case a
deferred DELETE overwrites a statement in a secondary index write set
and the overwritten statement wasn't skipped on commit (i.e. doesn't
have txv->is_overwritten flag set), both the old and the new statement
must be REPLACEs (see the comment to the corresponding assertions for
more details).

The problem is we don't set is_overwritten flag in case a statement
doesn't have any effect (txv->is_nop is set), even if it was, in fact,
overwritten in the primary index write set (see vy_tx_prepare). As
a result, we get an assertion failure when we delete such statement
in the same transaction, e.g.

  s = box.schema.space.create('test', {engine = 'vinyl'})
  s:create_index('pk', {parts = {1, 'unsigned'}})
  s:create_index('sk', {parts = {2, 'unsigned'}})
  s:replace{1, 1, 1}
  box.begin()
  s:update(1, {{'+', 3, 1}}) -- adds no-op REPLACE to sk write set
  s:delete(1)                -- produces deferred DELETE for sk
  box.commit()

results in

  vy_tx_handle_deferred_delete: Assertion `vy_stmt_type(stmt) == IPROTO_REPLACE' failed.

Fix this by making sure we set is_overwritten for all overwritten
statements in a secondary index write set.

Closes #4294

**Intro**:

By default, Lua uses package.path/cpath to load dependencies when user
calls `require("something")`. It also allows to add custom loaders to
extend its functionality. Tarantool transforms default behavior by
injecting some custom loaders into `package.loaders`.

Firstly, it allows to load modules from CWD. Secondly, it looks for
rocks modules starting from CWD and traversing up to root "/"
directory. This "start from CWD" behaviour is hardcoded and not
customizable.

**Problem**:

Let say we have a lua app with all dependencies under myapp directory.
If you start your application like this, you won't be able to load any
of them unless you specify myapp in every require call:

```bash
tarantool myapp/init.lua
```

To allow user scripts require dependencies relatively, user has to first
determine appropriate directory path relatively to scripts file and then
patch package.path/cpath with both modules and rocks paths.

**Solution**:

Introduce the notion of a search root which is used as base for rocks
and module loaders. Let user easily set this path to control how
application dependencies are loaded.

There is 2 new functions introduced in this patch:
- package.setsearchroot(path) is used to set new search root to look
dependency from
- package.searchroot() returns search root currently setup. If no search
root was setup, `fio.cwd()` is returned.

@TarantoolBot document
Title: Document new package.setsearchroot and package.searchroot
functions

What this patch does:

`package.setsearchroot(path)` function sets search root which is used
as root directory to load dependencies from:

- path must be a string (relative or absolute). It will be expanded to
  absolute path and set as a search root;
- if no path specified, it sets current file directory as a search root
  (using debug.sourcedir);
- if path is box.NULL, that searchroot will be reset,
  so default behaviour will apply (CWD).

With that said everything a user now has to do is to just put this line
of code:

```lua
package.setsearchroot()
```

at the top of project init file "myapp/init.lua" which is placed in the
project root and start an app by simply calling:

```bash
$ tarantool myapp/init.lua
```

This will set search root to the absolute path of `myapp` directory, so
all dependencies will be looked relative to that directory.

Iproto already listens for requests during recovery, so yielding at this
point of time allows such early requests, which arrived during recovery,
be processed while data is in unfinished state. This caused box/net.box
test failures, and is potentially harmful.
Besides, there is no need to yield during recovery.

Closes #4273

Add fixed-point decimal type to tarantool core.
Adapt decNumber floating-point decimal library for the purpose, write a
small wrapper and add unit tests.

A new decimal type is an alias for decNumber numbers from the decNumber
library.
Arithmetic operations (+, -, *, /) and some mathematic functions
(ln, log10, exp, pow, sqrt) are available together with methods to
pack and unpack decimal to and from its packed representation (useful
for serialization).

We introduce a single context for all the arithmetic operations
on decimals, which enforces both number precision and scale to be
in range [0, 38]. NaNs and Infinities are restricted.

Part of #692

After this patch, all errors in VDBE will be set using diag_set().

Closes #4074

After this patch, all errors in the SQL functions will be set
using diag_set().

Part of #4074

This patch replaces SQL error SQL_MISMATCH by Tarantool error
ER_SQL_TYPE_MISMATCH.

Since the interrupt system is no longer used in SQL, the
SQL_INTERRUPT error is out of date and should be removed. Also
this patch removes currently unused progress callback system.

Currently, in OP_Halt, you can get a SQL error other than
SQL_TARANTOOL_ERROR, for example, the SQL_CONSTRAINT error. After
this patch, all errors going through OP_Halt will have SQL error
code SQL_TARANTOOL_ERROR and have diag set.

Part of #4074

The ER_SQL error code is very similar to the ER_SQL_EXECUTE error
code: they have almost identical description and usage. To avoid
misunderstandings, it is better to remove one of them. The ER_SQL
error code has a slightly more vague description, so it was
decided to remove it.

The error codes SQL_TARANTOOL_DELETE_FAIL,
SQL_TARANTOOL_ITERATOR_FAIL and SQL_TARANTOOL_INSERT_FAIL have
practically no functions, but their use can lead to incorrect
behavior. This patch replaces them with SQL_TARANTOOL_ERROR. This
will simplify the work with errors.

Currently, the mayAbort field is working with SQL error
SQL_CONSTRAINT. Since we want to replace SQL_CONSTRAINT with a
Tarantool error, we need to change the way the mayAbort field
works or delete it. Since this field is used only for make an
assertion in debug mode, it is better to simply remove it.