Programming in JavaScript 

There are multiple wrappers for programming YottaDB in JavaScript.

Access from Bun is provided by mg-dbx-napi and mg_bun.
Access from Deno is provided by mg_deno.
Access from Node.js, is provided by Nodem (documented below), mg-dbx-napi, and mg-dbx.

The newer technology mg-dbx-napi wrapper has a more modern design and higher performance than the mg-dbx and mg_bun wrappers.

Nodem is developed by David Wicksell of Fourth Watch Software LC and the mg interfaces are developed by Chris Munt of MGateway Ltd. We would like to acknowledge their contributions and thank them for the value they add to the YottaDB community.

The wrappers wrap the YottaDB Simple API to provide access to global and local variables as well as the ability to call functions and procedures coded in M. They also provide the ability to connect to YottaDB remotely over a network.

Please access documentation for the MGateway wrappers at mg-dbx-napi, mg_bun, mg_deno, and mg-dbx. The documentation below is specific to Nodem.

Installation 

The minimum required version of Nodem is 0.20.4. It should run on every version of Node.js starting with version 0.12.0, through the current release (v20.6.0 at this time), as well as every version of IO.js. However, in the future, both Node.js and the V8 JavaScript engine at its core could change their APIs in a non-backwards compatible way, which might break Nodem for that version.

In order to use Nodem, YottaDB must be installed and configured correctly, including setting up the required YottaDB environment variables, or setting the appropriate options in the open() API. Make sure to have $ydb_dist set to the root of the YottaDB instance before compiling Nodem, whether manually or via npm. Node.js must be installed and working as well.

Install Nodem using the following command;

$ npm install nodem

Update to the latest version using the following command;

$ npm update nodem

The following steps need to be performed in order for YottaDB to find the Call-In table and the v4wNode.m routine that it maps to:

Copy v4wNode.m, located in the nodem/src directory, into a directory that is specified in the $ydb_routines path, or in the routinesPath property in the call to the open() API.
Set the $ydb_ci environment variable, or set the callinTable property in the call to the open() API, pointing to the file nodem.ci located in the nodem/resources directory.

Note

To build and install Nodem from scratch, use the instructions specified here.

Nodem API 

Arguments can be passed to the API methods in two ways:

using positional arguments, or
using a single JavaScript object

The output format varies depending on which method is used.

Before any of the API methods can be used, a YottaDB runtime instance needs to be created;

const ydb=require('nodem').Ydb();

Arguments as objects and the objects returned (on success or failure) described below may have comments (lines staring with //) that provide information about the arguments or type of value returned. For example:

If a comment consists of (optional) then the property (argument or returned value) is optional.
If a comment consists of a value within <> then it is the default value for that property.
Any other values present in the comment specifies the domain of values.

A function, taking two arguments (error and result), can be passed to an API method, as its last argument. This will call the API method asynchronously. Currently data(), function(), get(), increment(), kill(), lock(), merge(), nextNode(), order(), previous(), previousNode(), procedure(), set(), unlock(), and version() are the only methods that support asynchronous operation in addition to synchronous operation.

Example:

// get() being called synchronously
> ydb.get({global:'num'});
{ ok: true, global: 'num', data: 1, defined: true }

// get() being called asynchronously
> ydb.get({global:'num'}, (error,result) => {if (!error) {console.log('result:', result);}});
undefined
> result: { ok: true, global: 'num', data: 1, defined: true }

A full set of error codes and messages is in the YottaDB Messages and Recovery Procedures Manual. An error code and error message are returned as part of the object when a call to an API method fails.

Nodem Wrapper Functions 

data()

As a wrapper for the C function ydb_data_s(), data() provides information about whether or not a global or local variable node has data and/or children.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[]  // (optional)
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     defined:      number              // [0|1|10|11]
}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.data({global: 'Population'});
{ ok: true, global: 'Population', defined: 10 }
> ydb.data({global: 'Population', subscripts: ["USA"]});
{ ok: true, global: 'Population', subscripts: [ 'USA' ], defined: 11 }

To better understand the structure of the Population global variable node refer to the Concepts section. The Population global variable has been set as follows:

> ydb.set({global:'Population',subscripts:["USA"],data:325737000})
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA' ],
  data: 325737000
}
> ydb.set({global:'Population',subscripts:["USA",17900802],data:3929326})
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', 17900802 ],
  data: 3929326
}
> ydb.set({global:'Population',subscripts:["USA",18000804],data:5308483})
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', 18000804 ],
  data: 5308483
}
> ydb.set({global:'Population',subscripts:["USA",20100401],data:308745538})
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', 20100401 ],
  data: 308745538
}
> ydb.set({global:'Population',subscripts:["Belgium"],data:1367000})
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Belgium' ],
  data: 1367000
}
> ydb.set({global:'Population',subscripts:["Thailand"],data:8414000})
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Thailand' ],
  data: 8414000
}

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{number} [0|1|10|11]

Returns the following on failure:

{Error object}

Example:

> ydb.data('^Population');
10
> ydb.data('^Population', 'Belgium');
11
>

get()

As a wrapper for the C function ydb_get_s(), get() gets data from a global variable node, local variable node, or an intrinsic special variable.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[]  // (optional)
}

To get the value of an ISV, use the local property. See example below.

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     data:         string|number,
     defined:      boolean
}

Note

get() returns an empty string if a variable does not exist.

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.get({global:'Population'});
{ ok: true, global: 'Population', data: '', defined: false }
> ydb.get({global:'Population', subscripts: ["Belgium"]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Belgium' ],
  data: 3250000,
  defined: true
}
> ydb.get({global:'Population', subscripts: ['Belgium',20100401]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Belgium', 20100401 ],
  data: 10938740,
  defined: true
}
> ydb.get({local:'$zgbldir'})
{
  ok: true,
  local: '$zgbldir',
  data: '/home/ydbuser/.yottadb/r1.34_x86_64/g/yottadb.gld',
  defined: true
}
>

Positional arguments:

^global|$ISV|local, [subscripts+]

Returns the following on success:

{string|number}

Returns the following on failure:

{Error object}

Example:

> ydb.get('^Population', 'Belgium');
3250000
> ydb.get('^Population', 'USA', 20100401);
308745538
> ydb.get('$ZGBLDIR');
'/home/ydbuser/.yottadb/r1.34_x86_64/g/yottadb.gld'
>

increment()

As a wrapper for the C function ydb_incr_s(), increment() atomically increments the value in a global or local variable node.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     increment:    number              // <1> (optional)
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     increment:    number,
     data:         string|number
}

When the data property is a string, it is the string representation of a canonical number.

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.get({local:'num'});
{ ok: true, local: 'num', data: 4, defined: true }
> ydb.increment({local:'num'});
{ ok: true, local: 'num', increment: 1, data: 5 }
>

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{string|number}

Returns the following on failure:

{Error object}

Example:

> ydb.get('^Z');
155
> ydb.increment('^Z');
156
>

kill()

As a wrapper for the C function ydb_delete_s(), kill() deletes a global or local variable node, or the entire tree.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     nodeOnly:     boolean             // <false> (optional)
}

If no arguments are passed to kill(), then all of the local variable nodes will be deleted.

Returns the following object on success, if arguments are passed:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     nodeOnly:     boolean
}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.localDirectory();
[ 'num', 'y' ]
> ydb.kill();
undefined
> ydb.localDirectory();
[]
> ydb.kill({global:'z'});
{ ok: true, global: 'z', nodeOnly: false }

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{undefined}

Returns the following on failure:

{Error object}

Example:

> ydb.get('^Z');
156
> ydb.kill('^Z');
undefined
> ydb.get('^Z');
''

lock()

As a wrapper for the C function ydb_lock_incr_s(), lock() locks a global or local variable node, incrementally.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     timeout:      number              // (optional)
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     timeout:      number,
     result:       boolean
}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{boolean}

Returns the following on failure:

{Error object}

nextNode()

nextNode() returns the next global or local variable node. It wraps the C function ydb_node_next_s(), and then uses ydb_get_s() to get the value of the next node.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[]  // (optional)
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     data:         string|number,
     defined:      boolean
}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.nextNode({global: 'Population'});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Belgium' ],
  data: 1367000,
  defined: true
}
> ydb.nextNode({global: 'Population', subscripts: ["Belgium"]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Thailand' ],
  data: 8414000,
  defined: true
}
> ydb.nextNode({global: 'Population', subscripts: ["Thailand"]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA' ],
  data: 325737000,
  defined: true
}
> ydb.nextNode({global: 'Population', subscripts: ["USA"]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', 17900802 ],
  data: 3929326,
  defined: true
}
> ydb.nextNode({global: 'Population', subscripts: ["USA",17900802]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', 18000804 ],
  data: 5308483,
  defined: true
}
>

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{string[]|number[]}

Returns the following on failure:

{Error object}

Example:

> ydb.nextNode('^Population', 'USA');
[ 'USA', 17900802 ]
> ydb.nextNode('^Population', 'USA', 17900802);
[ 'USA', 18000804 ]
> ydb.nextNode('^Population', 'USA', 18000804);
[ 'USA', 20100401 ]
> ydb.nextNode('^Population', 'USA', 20100401);
[]

order()/next()

As a wrapper for the C function ydb_subscript_next_s(), order() returns the next global or local variable subscript at the same level.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[]   // (optional)
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     result:       string|number
}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.order({global: 'Population', subscripts: ["Thailand"]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA' ],
  result: 'USA'
}
> ydb.order({global: 'Population', subscripts: ["USA"]});
{ ok: true, global: 'Population', subscripts: [ '' ], result: '' }
> ydb.order({global: 'Population', subscripts: ["USA",17900802]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', 18000804 ],
  result: 18000804
}
> ydb.order({global: 'Population', subscripts: ["USA",18000804]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', 20100401 ],
  result: 20100401
}

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{string|number}

Returns the following on failure:

{Error object}

Example:

> ydb.order('^Population','Belgium');
'Thailand'
> ydb.order('^Population','Thailand');
'USA'
> ydb.order('^Population','USA');
''
>

previous()

As a wrapper for the C function ydb_subscript_previous_s(), previous() returns the previous global or local variable subscript at the same level.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[]  // (optional)
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     result:       string|number
}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.previous({global: 'Population', subscripts: ["USA",18000804]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', 17900802 ],
  result: 17900802
}
> ydb.previous({global: 'Population', subscripts: ["USA",17900802]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA', '' ],
  result: ''
}
>

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{string|number}

Returns the following on failure:

{Error object}

Example:

> ydb.previous('^Population','USA', 18000804);
17900802
> ydb.previous('^Population','USA', 17900802);
''
> ydb.previous('^Population','USA');
'Thailand'
>

previousNode()

previousNode() returns the previous global or local variable node. It wraps the C function ydb_node_previous_s(), and then uses ydb_get_s() to get the value of the previous node.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[]  // (optional)
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     data:         string|number,
     defined:      boolean
}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.previousNode({global: 'Population', subscripts: ["USA",17900802]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'USA' ],
  data: 325737000,
  defined: true
}
> ydb.previousNode({global: 'Population', subscripts: ["USA"]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Thailand' ],
  data: 8414000,
  defined: true
}
>

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{string[]|number[]}

Returns the following on failure:

{Error object}

Example:

> ydb.previousNode('^Population','USA', 17900802);
[ 'USA' ]
> ydb.previousNode('^Population','USA');
[ 'Thailand' ]
> ydb.previousNode('^Population','Thailand');
[ 'Belgium', 20100401 ]
> ydb.previousNode('^Population','Belgium', 20100401);
[ 'Belgium', 18000804 ]
>

set()

As a wrapper for C function ydb_set_s(), set() sets a global variable node, local variable node, or an intrinsic special variable.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     data:         string|number
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[],  // (optional)
     data:         string|number
}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.set({local:'y', data:'Hello'})
{ ok: true, local: 'y', data: 'Hello' }
>

Positional arguments:

^global|$ISV|local, [subscripts+], data

Returns the following on success:

{undefined}

Returns the following on failure:

{Error object}

Example:

> ydb.set('lclvar1',5);
undefined
> ydb.get('lclvar1');
5
> ydb.set('lclvar1','first', 10);
undefined
> ydb.get('lclvar1','first');
10
>

transaction()

As a wrapper for C function ydb_tp_s(), it provides support for full ACID transactions.

It requires, as the first argument, a JavaScript function that takes no arguments. This function can contain in itself, other Nodem calls, nested transaction() calls, or any other JavaScript code. By default no local variables are reset during transaction restarts.

Note

The JavaScript function is run synchronously within the transaction by YottaDB, and every Nodem API that is called within the transaction must also be run synchronously.

An optional second argument, with one or two properties, can be passed to transaction():

The first property, variables, is an array of local variables whose values are reset to their original values whenever the transaction is restarted. If variables has * as its only array item, then every local variable will be reset during a transaction restart.
The second property, type, is a string which if set to Batch (or batch or BATCH), will run the transaction in batch mode. Batch mode does not ensure Durability (but it always ensures Atomicity, Consistency, and Isolation).

In order to restart a transaction pass the string Restart (or restart, RESTART, or the tpRestart property) as the argument to the return statement. Similarly, in order to rollback a transaction pass the string Rollback (or rollback, ROLLBACK, or the tpRollback property) as the argument to the return statement. Any other argument to the return statement will commit the transaction, including functions without a return statement.

Returns the following on success:

{
     ok:            boolean,  // true
     statusCode:    number,
     statusMessage: string
}

Returns the following on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

const ydb=require('nodem').Ydb();
ydb.open();

console.log("Value of ^num before transaction: ", ydb.set({ global: 'num', data: 0 }));

const transResult = ydb.transaction(() => {
    console.log("Starting transaction ... \n");
    let incrementGlobal = ydb.increment({ global: 'num'});
    if (incrementGlobal.errorCode === ydb.tpRestart) return 'Restart';
    if (!incrementGlobal.ok) return 'Rollback';
    console.log("Incrementing ^num: ", incrementGlobal);

    const result = ydb.get({ global: 'num'});
    if (result.errorCode === ydb.tpRestart) return 'Restart';
    if (!result.ok) return 'Rollback';
    console.log("^num: ", result);

    return 'Commit';
}, { variables: ['*'] });

console.log("Transaction exited ... \n");
console.log("Transaction output: ", transResult);

Output:

Value of ^num before transaction:  { ok: true, global: 'num', data: 0 }
Starting transaction ...

Incrementing ^num:  { ok: true, global: 'num', increment: 1, data: 1 }
^num:  { ok: true, global: 'num', data: 1, defined: true }
Transaction exited ...

Transaction output:  { ok: true, statusCode: 0, statusMessage: 'Commit' }

Even though the transaction() API runs synchronously, it is fully compatible with the Worker Threads API. By creating a new worker thread and running the transaction() API, and any other APIs it calls in it, an asynchronous pattern can be emulated. Running the transaction will not block the main thread or any of the other worker threads. The transaction.js example shows how the transaction() API can be used with the Worker Threads API. See Worker Threads API for more information.

unlock()

As a wrapper for C function ydb_lock_decr_s, unlock() decrements the count of the specified lock held by the process.

Arguments as an object:

{
     global|local: string,
     subscripts:   string[]|number[]  // (optional)
}

Returns the following object on success:

{
     ok :          boolean,            // true
     global|local: string,
     subscripts:   string[]|number[]   // (optional)
}

If no arguments are passed to unlock(), then all of the currently held locks will be released.

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Positional arguments:

^global|local, [subscripts+]

Returns the following on success:

{undefined}

Returns the following on failure:

{Error object}

Other API Functions 

close()

Cleans up the process connection and/or the access to all the databases. Once the connection is closed, it cannot be reopened during the lifetime of the current process.

Arguments as an object:

{
     resetTerminal:   boolean  // <false> (optional)
}

By setting the resetTerminal property to true, the terminal settings will be reset once the connection to YottaDB has been closed.

Returns the following on success:

{undefined}

Returns the following object on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.close();
undefined

configure()

Configures the parameters for the current thread's connection to YottaDB.

Arguments as an object:

// All of the following arguments are optional

{
     charset|encoding: string,                 // [<utf8|utf-8>|m|binary|ascii]
     mode:             string,                 // [<canonical>|string]
     autoRelink:       boolean,                // <false>
     debug:            boolean|string|number   // <false>|[<off>|low|medium|high]|[<0>|1|2|3]
}

Returns the following on success:

{
     ok:     boolean,  // true
     pid:    number,
     tid:    number
}

Example:

> const ydb=require('nodem').Ydb();
undefined
> ydb.open();
{ ok: true, pid: 66935, tid: 66935 }
> ydb.configure({charset:'utf8', mode:'canonical', debug:2});
[C 66935] DEBUG>  Nodem::configure enter
[C 66935] DEBUG>>   debug: medium
[C 66935] DEBUG>>   autoRelink: false
[C 66935] DEBUG>>   mode: canonical
[C 66935] DEBUG>>   charset: utf-8
[C 66935] DEBUG>>   stat_buf: 0
[C 66935] DEBUG>  Nodem::configure exit

{ ok: true, pid: 66935, tid: 66935 }
>

function()

function() is used to call an extrinsic (user-defined) function in M code. See Extrinsic Functions for more information.

Arguments as an object:

{
     function:   string,
     arguments:  string[]|number[]|[],  // (optional)
     autoRelink: boolean                // <false> (optional)
}

Returns the following on success:

{
     ok:         boolean,               // true
     function:   string,
     arguments:  string[]|number[]|[],  // (optional)
     autoRelink: boolean,
     result:     string|number
}

Returns the following on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example;

> ydb.function({function: '^HELLOWORLD()'});
{
  ok: true,
  function: 'HELLOWORLD()',
  autoRelink: false,
  result: 'Hello World'
}

where HELLOWORLD routine is defined as follows:

YDB>ZPRINT ^HELLOWORLD
HELLOWORLD()
        QUIT "Hello World"

Positional arguments:

function, [arguments+]

Returns the following on success:

{string|number}

Returns the following on failure:

{Error object}

Example:

> ydb.function('^HELLOWORLD()');
'Hello World'
>

globalDirectory()

Lists all the global variables stored in the database.

Arguments as an object:

// All of the following arguments are optional

{
     max: number,
     lo:  string,
     hi:  string
}

max can be used to limit the number of global variables that are listed. Setting lo and hi will only display the global variables that are between those values, with lo included and hi excluded. If only lo is set, then the interval ends at the last global variable. Whereas if only hi is set then the interval starts at the first global variable. See example below.

Returns the following on success:

[
     <global variable name>*  string
]

Returns the following on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.globalDirectory();
[
  'Crab',
  'Horse',
  'hello',
  'num',
  'v4wTest',
  'x',
  'y'
]
> ydb.globalDirectory({max:2});
[ 'Crab', 'Horse' ]
> ydb.globalDirectory({lo:'v', hi:'z'});
[ 'v4wTest', 'x', 'y' ]

localDirectory()

Lists all the local variables defined in the current scope.

Arguments as an object:

// All of the following arguments are optional

{
     max: number,
     lo:  string,
     hi:  string
}

max can be used to limit the number of local variables that are listed. Setting lo and hi will only display the local variables that are between those values, with lo included and hi excluded. If only lo is set, then the interval ends at the last local variable. Whereas if only hi is set then the interval starts at the first local variable. See example below.

Returns the following on success:

[
     <local variable name>*  string
]

Returns the following on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.set({local: 'day', data: 'Friday'});
{ ok: true, local: 'day', data: 'Friday' }
> ydb.set({local: 'month', data: 'April'});
{ ok: true, local: 'month', data: 'April' }
> ydb.set({local: 'date', data: 15});
{ ok: true, local: 'date', data: 15 }
> ydb.localDirectory();
[ 'date', 'day', 'month' ]
> ydb.localDirectory({hi:'l'});
[ 'date', 'day' ]
>

merge()

merge() is used to copy the entire tree or sub-tree from a global or local variable node, to another global or local variable node.

Arguments as an object:

{
     from: {
             global|local: string,
             subscripts:   string[]|number[]  // (optional)
           },
     to:   {
             global|local: string,
             subscripts:   string[]|number[]  // (optional)
           }
}

Returns the following on success:

{
     ok:   boolean,                           // true
     from: {
             global|local: string,
             subscripts:   string[]|number[]  // (optional)
           },
     to:   {
             global|local: string,
             subscripts:   string[]|number[]  // (optional)
           }
}

Returns the following on failure:

{
     ok :          boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.merge({ from: {global: 'PopBelgium'}, to: { global: 'Population', subscripts: ['Belgium']}});
{
  ok: true,
  from: { global: 'PopBelgium' },
  to: { global: 'Population', subscripts: [ 'Belgium' ] }
}
> ydb.get({global:'Population', subscripts: ['Belgium',18000804]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Belgium', 18000804 ],
  data: 3250000,
  defined: true
}
> ydb.get({global:'Population', subscripts: ['Belgium',20100401]});
{
  ok: true,
  global: 'Population',
  subscripts: [ 'Belgium', 20100401 ],
  data: 10938740,
  defined: true
}

Where the PopBelgium global variable node has been set as follows:

> ydb.set({global: 'PopBelgium', subscripts: [ 18000804 ], data:3250000});
{
  ok: true,
  global: 'PopBelgium',
  subscripts: [ 18000804 ],
  data: 3250000
}
> ydb.set({global: 'PopBelgium', subscripts: [ 20100401 ], data:10938740});
{
  ok: true,
  global: 'PopBelgium',
  subscripts: [ 20100401 ],
  data: 10938740
}

open()

open() is used to initialize the YottaDB runtime environment. All the methods, except help() and version(), require the YottaDB runtime environment to be initialized.

Arguments as an object:

// All of the following arguments are optional

{
     globalDirectory|namespace: string,                 // <none>
     routinesPath:              string,                 // <none>
     callinTable:               string,                 // <none>
     ipAddress:                 string,                 // <none>
     tcpPort:                   number|string,          // <none>
     charset|encoding:          string,                 // [<utf8|utf-8>|m|binary|ascii]
     mode:                      string,                 // [<canonical>|string]
     autoRelink:                boolean,                // <false>
     debug:                     boolean|string|number,  // <false>|[<off>|low|medium|high]|[<0>|1|2|3]
     threadpoolSize:            number,                 // [1-1024] <4>
     signalHandler:             boolean|object          // <true>
}

where the signalHandler object is as follows:

{
     sigint|SIGINT:   boolean,  // <true> (optional)
     sigterm|SIGTERM: boolean,  // <true> (optional)
     sigquit|SIGQUIT: boolean   // <true> (optional)
}

The ipAddress and tcpPort properties are used to configure Nodem as a GT.CM client. See GT.CM Client section for more information.

Returns the following on success:

{
     ok:     boolean  // true
     pid:    number
     tid:    number
}

Returns the following on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.open();
{ ok: true, pid: 77379, tid: 77379 }

procedure()/routine()

Call a procedure or routine label in M code. It is similar to the function() API, except that procedure() is used to call M procedures or routines that do not return any values.

Arguments as an object:

{
     procedure|routine: string,
     arguments:         string[]|number[]|[],  // (optional)
     autoRelink:        boolean                // <false> (optional)
}

Returns the following on success:

{
     ok:                boolean,               // true
     procedure|routine: string,
     arguments:         string[]|number[]|[],  // (optional)
     autoRelink:        boolean
}

Returns the following on failure:

{
     ok:           boolean,  // false
     errorCode:    number,
     errorMessage: string
}

Example:

> ydb.procedure({procedure: '^TESTPRCDR', arguments: [155]});
{
  ok: true,
  procedure: 'TESTPRCDR',
  arguments: [ 155 ],
  autoRelink: false
}
> ydb.get({global: 'Z'})
{ ok: true, global: 'Z', data: 155, defined: true }
>

where ^TESTPRCDR routine is defined as follows:

YDB>zprint ^TESTPRCDR
TESTPRCDR(VAL)
        SET ^Z=VAL

Positional arguments:

procedure, [arguments+]

Returns the following on success:

{undefined}

Returns the following on failure:

{Error object}

Example:

> ydb.get('^Z');
155
> ydb.procedure('TESTPRCDR', 175)
undefined
> ydb.get('^Z');
175
>

version()/about()

Displays the version data. It includes the YottaDB version if the runtime has been initialized.

No arguments are needed for version().

Returns the following on success:

{string}

Returns the following on failure:

{Error object}

Example:

Welcome to Node.js v12.22.5.
Type ".help" for more information.
> const ydb=require('nodem').Ydb();
undefined
> ydb.version();
'Node.js Adaptor for YottaDB: Version: 0.20.4 (ABI=72) [FWS]'
> ydb.open();
{ ok: true, pid: 20381, tid: 20381 }
> ydb.version();
'Node.js Adaptor for YottaDB: Version: 0.20.4 (ABI=72) [FWS]; YottaDB Version: 1.34'

Programming Notes 

The open() call does not require any arguments, and connects the YottaDB runtime system to the Global Directory specified by the environment variable $ydb_gbldir. To use a different Global Directory, than the one defined by $ydb_gbldir, pass an object, to the open() API, with a property called either globalDirectory or namespace, defined as the path to the global directory file for that database, e.g.,

> ydb.open({globalDirectory: process.env.HOME + '/g/db_utf8.gld'});

Calling M routines 

Nodem supports setting up a custom routines path, for resolving calls to M functions and procedures, via the routinesPath property. By controlling routinesPath an application can control the M routines that Node.js application code can call, e.g.,

> const HOME = process.env.HOME;
> ydb.open({routinesPath: `${HOME}/p/r1.34_x86_64(${HOME}/p)`});

Nodem also supports setting the Call-In path directly in the open() call via the callinTable property. This can be handy if Nodem is being run in an environment that has other software that uses the YottaDB Call-In Interface, thus not causing any namespace issues. There is no need to set the $ydb_ci environment variable in order for Nodem to be fully functional, e.g.,

> ydb.open({callinTable: process.env.HOME + '/nodem/resources/nodem.ci'});

GT.CM Client 

Nodem can be configured to function as a GT.CM client, allowing it to connect with a remote database. The ipAddress and/or tcpPort property can be set in the open() method, allowing Nodem to set up the environment to connect with a YottaDB database on a remote server that already has a GT.CM server listening at that address and port. If only ipAddress or tcpPort is defined, the other one will be set with a default value; 127.0.0.1 for ipAddress, or 6789 for tcpPort. Nodem will then set the $ydb_cm_NODEM environment variable for that Nodem process only, with the address and port in the open() call, e.g.,

> ydb.open({ipAddress: '127.0.0.1', tcpPort: 6789});

If using IPv6, surround the IP address with square brackets, e.g.,

> ydb.open({ipAddress: '[::1]', tcpPort: 6789});

A global directory file will need to be created or modified. It should map one or more database segments to a data file on the remote server being connected to. Note that the prefix to the -file= argument in the example below must be NODEM, in order to match the $ydb_cm_NODEM environment variable name that Nodem sets up.

$ $ydb_dist/mumps -run GDE
GDE> change -segment DEFAULT -file=NODEM:/home/ydbuser/g/gtm-server.dat

Make sure to have the data file, on the remote server, set up to the same path as the -file= option in the global directory of the GT.CM client configuration. Start the GT.CM server on the same IP address and port as configured in the open() call in Nodem.

$ $ydb_dist/gtcm_gnp_server -log=gtcm.log -service 6789

Note

GT.CM only allows remote connections for the database access APIs, not the function() or procedure() APIs. So while using Nodem in a remote GT.CM configuration, any call to the function() or procedure() APIs will result in local calls, not remote RPC calls. Also, nodes accessed by GT.CM cannot participate in transactions.

Character Encodings 

Nodem supports two different character encodings, UTF-8 and M. It defaults to UTF-8 mode. M mode is similar to ASCII, except that it utilizes all 8 bits in a byte and collates slightly differently. Instead of collation based only on the character codes themselves, it sorts numbers before everything else. The character encoding that is set in Nodem is decoupled from the underlying character encoding set up for the YottaDB environment it is running in. So it is possible to work with UTF-8 encoded data in the database, while in Nodem, even if YottaDB hasn't been set up to work with UTF-8 directly. It can be set to UTF-8 mode directly by passing utf-8 or utf8, case insensitively, to the charset property. To work with an older byte-encoding scheme, that stores all characters in a single byte, set charset to either m, ascii, or binary, case insensitively. One thing to keep in mind is that Node.js internally stores data in UTF-16, but interprets data in UTF-8 in most cases. This can be controlled through the process stream encoding methods inside the Node.js code. Calling those methods to change the encoding to binary or ascii, will interpret the data as a byte encoding, using the character glyphs in the current locale, e.g.,

> process.stdin.setEncoding('binary');
> process.stdout.setDefaultEncoding('binary');
> ydb.open({charset: 'm'}); // For all threads

or

> process.stdin.setEncoding('binary');
> process.stdout.setDefaultEncoding('binary');
> ydb.configure({charset: 'm'}); // For the current thread

Data Handling 

There are currently two different modes that Nodem supports for handling data, both in subscripts and in nodes. The mode can be set to canonical or string. The default is canonical, and interprets data using the M canonical representation i.e., numeric data will be represented numerically, rather than as strings, and numeric subscripts will collate before string subscripts. The other mode, string, interprets all data as strings, e.g.,

> ydb.open({mode: 'string'}); // For all threads

or

> ydb.configure({mode: 'string'}); // For the current thread

Debugging Mode 

Nodem also has a debug tracing mode, in case something doesn't seem to be working right, or to see what happens to data as it moves through the Nodem APIs. It has four levels of debugging, defaulting to off. The other debug levels are low, medium, and high. Numbers from 0-3 can also be used. The higher the debug level, the more verbose the debug output will be, e.g.,

> ydb.open({debug: 'low'}); // For all threads
[C 32649] DEBUG>  Nodem::open enter
[C 32649] DEBUG>  debug: low
[C 32649] DEBUG>  Nodem::open exit

{ ok: true, pid: 32649, tid: 32649 }

or

> ydb.open({debug: 2}); // For all threads

or

> ydb.configure({debug: 'high'}); // For the current thread

Signal Handling 

Nodem handles several common signals that are typically used to stop processes, by cleaning up the process connection, resetting the controlling terminal configuration, and stopping the Node.js process. These signals include SIGINT, SIGTERM, and SIGQUIT. The handling of the SIGQUIT signal will also generate a core dump of the process. All three signal handlers are on by default. However, the signal handling can be turned on or off directly, via passing true or false to a signalHandler object (with properties for each of the signals) for each individual signal, or all of them at once, e.g.,

> ydb.open({signalHandler: {sigint: true, sigterm: false, sigquit: false}});

or

> ydb.open({signalHandler: false});

Auto-relinking 

Nodem supports a feature called auto-relink, which will automatically relink a routine object containing any function or procedure called by the function() or procedure() API. By default auto-relink is off. It can be enabled in one of four ways. First, pass it as a property of the JavaScript object argument which is passed to the function() or procedure() API directly, with a value of true. This will turn on auto-relink just for that call. It can also be disabled, by setting autoRelink to false if it was already enabled by one of the global settings, e.g.,

> ydb.function({function: 'version^v4wTest', autoRelink: true});

Second, it can be enabled globally, for every thread, and for every call to the function() (or procedure()) API, by setting the same property in a JavaScript object passed to the open() API, e.g.,

> ydb.open({autoRelink: true});

Third, it can be enabled globally, for the current thread, for every call to the function() (or procedure()) API, by setting the same property in a JavaScript object passed to the configure API, e.g.,

> ydb.configure({autoRelink: true});

Fourth, it can also be enabled globally, for every thread, by setting the environment variable NODEM_AUTO_RELINK to 1, or any other non-zero number, e.g.

$ export NODEM_AUTO_RELINK=1
$ node function.js

or

$ NODEM_AUTO_RELINK=1 node function.js

Asynchronous Calls 

Nodem's asynchronous APIs do their work in a separate thread pool, pre-allocated by Node.js via libuv. By default, four threads are created, and will take turns executing asynchronous calls, including asynchronous calls from other non-Nodem APIs. Nodem supports setting a different value for the pre-allocated thread pool for asynchronous calls, in its open() API, up to a max of 1024, in the latest versions of Node.js, e.g.,

> ydb.open({threadpoolSize: 1024});

However, if the Node.js process executes any call asynchronously, from any API or module, before the YottaDB runtime environment has been initialized, then the threadpoolSize property is ignored. So make sure to use open(), to initialize the runtime environment first in any process, so as to control how large the pre-allocated thread pool is.

Note

The Node.js core worker_thread API, which also allocates threads from the same worker thread pool in libuv, allows complete control of creating and destroying threads, and does not utilize the threadpoolSize (which just sets the libuv environment variable UV_THREADPOOL_SIZE) set in the Nodem open() API.

Restoring Terminal Settings 

YottaDB changes some settings of its controlling terminal device, and Nodem resets them when it closes the database connection. By default, Nodem will restore the terminal device to the state it was in when the open() call was invoked. Normally this is the desired option; however, the close() call allows setting the terminal to typically sane settings, by setting the resetTerminal property to true, e.g.,

> ydb.close({resetTerminal: true});

Worker Threads API 

Nodem supports the Worker Threads API, for both synchronous and asynchronous calls. Since YottaDB is single threaded, initializing and cleaning up the runtime environment (i.e., using open() and close()) should only be done once during the process lifetime. Nodem's open() and close() APIs will only work when called from the main thread of the process. In order to work with the worker threads API, open() should be called in the main thread before creating any worker threads, and close() should be called in the main thread after all the worker threads have exited. To have access to the Nodem API, Nodem should be required in each worker thread as well as the main thread.

Nodem has the configure() API which allows the worker threads to change the database configuration options of the current thread. There are four configuration options that can be set for the current thread: charset, mode, autoRelink, and debug. These options can be set in the open() API, by the main thread, before any other Nodem calls are made, or they can be set in the configure() API, in the main thread or worker threads, at any time.