EJDB 2.0

EJDB2 is an embeddable JSON database engine published under MIT license.

C11 API
Single file database
Simple but powerful query language (JQL) as well as support of the following standards:
- rfc6902 JSON Patch
- rfc7386 JSON Merge patch
- rfc6901 JSON Path
Powered by iowow.io - The persistent key/value storage engine
Provides HTTP REST/Websockets network endpoints with help of facil.io
JSON documents are stored in using fast and compact binn binary format

Native language bindings

Dart https://pub.dartlang.org/packages/ejdb2_dart
Java ejdb2_jni/README.md
Android support (see below)

Status

EJDB 2.0 is currently in BETA, stable enough but some gotchas may be arised
Tested on Linux and OSX platforms
Windows platform not supported at now #237
Old EJDB 1.x version can be found in separate ejdb_1.x branch. We are not maintaining ejdb 1.x.

Supported platforms

OSX

EJDB2 code ported and tested on OSX High Sierra

mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release
make

Linux

Ubuntu/Debian

PPA repository

sudo add-apt-repository ppa:adamansky/ejdb2
sudo apt-get update
sudo apt-get install ejdb2

Building debian packages

mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -DPACKAGE_DEB=ON
make package

RPM based Linux distributions

mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -DPACKAGE_RPM=ON
make package

Android

Android binding showcase and unit tests

cd ./src/bindings/ejdb2_android

Set local android SDK/NDK path and target arch in local.properties

# Path to Android SDK dir
sdk.dir=/Android-sdk

# Path to Android NDK dir
ndk.dir=/Android-sdk/ndk-bundle

# Target abi name: armeabi-v7a, arm64-v8a, x86, x86_64
abi.name=arm64-v8a

Run Android emulator for the same abi version then:

./gradlew connectedAndroidTest

JQL

EJDB query language (JQL) syntax inspired by ideas behind XPath and Unix shell pipes. It designed for easy querying and updating sets of JSON documents.

JQL grammar

JQL parser created created by peg/leg — recursive-descent parser generators for C Here is the formal parser grammar: https://github.com/Softmotions/ejdb/blob/master/src/jql/jqp.leg

Non formal JQL grammar adapted for brief overview

Notation used below is based on SQL syntax description:

Rule	Description
`' '`	String in single quotes denotes unquoted string literal as part of query.
`{ a \| b }`	Curly brackets enclose two or more required alternative choices, separated by vertical bars.
`[ ]`	Square brackets indicate an optional element or clause. Multiple elements or clauses are separated by vertical bars.
`\|`	Vertical bars separate two or more alternative syntax elements.
`...`	Ellipses indicate that the preceding element can be repeated. The repetition is unlimited unless otherwise indicated.
`( )`	Parentheses are grouping symbols.
Unquoted word in lower case	Denotes semantic of some query part. For example: `placeholder_name` - name of any placeholder.

QUERY = FILTERS [ '|' APPLY ] [ '|' PROJECTIONS ] [ '|' OPTS ];

STR = { quoted_string | unquoted_string };

JSONVAL = json_value;

PLACEHOLDER = { ':'placeholder_name | '?' }

FILTERS = FILTER [{ and | or } [ not ] FILTER];

  FILTER = [@collection_name]/NODE[/NODE]...;

  NODE = { '*' | '**' | NODE_EXPRESSION | STR };

  NODE_EXPRESSION = '[' NODE_EXPR_LEFT OP NODE_EXPR_RIGHT ']'
                        [{ and | or } [ not ] NODE_EXPRESSION]...;

  OP =   [ '!' ] { '=' | '>=' | '<=' | '>' | '<' }
      | [ '!' ] { 'eq' | 'gte' | 'lte' | 'gt' | 'lt' }
      | [ not ] { 'in' | 'ni' | 're' };

  NODE_EXPR_LEFT = { '*' | '**' | STR | NODE_KEY_EXPR };

  NODE_KEY_EXPR = '[' '*' OP NODE_EXPR_RIGHT ']'

  NODE_EXPR_RIGHT =  JSONVAL | STR | PLACEHOLDER

APPLY = 'apply' { PLACEHOLDER | json_object | json_array  } | 'del'

OPTS = { 'skip' n | 'limit' n | 'count' | 'noidx' | ORDERBY }...

  ORDERBY = { 'asc' | 'desc' } PLACEHOLDER | json_path

PROJECTIONS = PROJECTION [ {'+' | '-'} PROJECTION ]

  PROJECTION = 'all' | json_path

json_value: Any valid JSON value: object, array, string, bool, number.
json_path: Simplified JSON pointer. Eg.: /foo/bar or /foo/"bar with spaces"/
* in context of NODE: Any JSON object key name at particular nesting level.
** in context of NODE: Any JSON object key name at arbitrary nesting level.
* in context of NODE_EXPR_LEFT: Key name at specific level.
** in context of NODE_EXPR_LEFT: Nested array value of array element under specific key.

JQL quick introduction

Lets play with some very basic data and queries. For simplicity we will use ejdb websocket network API which provides us a kind of interactive CLI. The same job can be done using pure C API too (ejdb2.h jql.h).

NOTE: Take a look into JQL test cases for more examples.

{
  "firstName": "John",
  "lastName": "Doe",
  "age": 28,
  "pets": [
    {"name": "Rexy rex", "kind": "dog", "likes": ["bones", "jumping", "toys"]},
    {"name": "Grenny", "kind": "parrot", "likes": ["green color", "night", "toys"]}
  ]
}

Save json as sample.json then upload it the family collection:

# Start HTTP/WS server protected by some access token
./jbs -a 'myaccess01'
8 Mar 16:15:58.601 INFO: HTTP/WS endpoint at localhost:9191

Server can be accessed using HTTP or Websocket endpoint. More info

curl -d '@sample.json' -H'X-Access-Token:myaccess01' -X POST http://localhost:9191/family

We can play around using interactive wscat websocket client.

wscat  -H 'X-Access-Token:myaccess01' -q -c http://localhost:9191
connected (press CTRL+C to quit)
> k info
< k     {
 "version": "2.0.0",
 "file": "db.jb",
 "size": 8192,
 "collections": [
  {
   "name": "family",
   "dbid": 3,
   "rnum": 1,
   "indexes": []
  }
 ]
}

> k get family 1
< k     1       {
 "firstName": "John",
 "lastName": "Doe",
 "age": 28,
 "pets": [
  {
   "name": "Rexy rex",
   "kind": "dog",
   "likes": [
    "bones",
    "jumping",
    "toys"
   ]
  },
  {
   "name": "Grenny",
   "kind": "parrot",
   "likes": [
    "green color",
    "night",
    "toys"
   ]
  }
 ]
}

Note about the k prefix before every command; It is an arbitrary key choosen by client and designated to identify particular websocket request, this key will be returned with response to request and allows client to identify that response for his particular request. More info

Query command over websocket has the following format:

<key> query <collection> <query>

So we will consider only <query> part in this document.

Get all elements in collection

k query family /*

or

k query family /**

or specify collection name in query explicitly

k @family/*

We can execute query by HTTP POST request

curl --data-raw '@family/[firstName=John]' -H'X-Access-Token:myaccess01' -X POST http://localhost:9191

1	{"firstName":"John","lastName":"Doe","age":28,"pets":[{"name":"Rexy rex","kind":"dog","likes":["bones","jumping","toys"]},{"name":"Grenny","kind":"parrot","likes":["green color","night","toys"]}]}

Set the maximum number of elements in result set

k @family/* | limit 10

Get documents where specified json path exists

Element at index 1 exists in likes array within a pets sub-object

> k query family /pets/*/likes/1
< k     1       {"firstName":"John"...

Element at index 1 exists in likes array at any likes nesting level

> k query family /**/likes/1
< k     1       {"firstName":"John"...

From this point and below I will omit websocket specific prefix k query family and consider only JQL queries.

Matching JSON entry values

Below is a set of self explaining queries:

/pets/*/[name = "Rexy rex"]

/pets/*/[name eq "Rexy rex"]

/pets/*/[name = "Rexy rex" or name = Grenny]

Note about quotes around words with spaces.

Get all documents where owner age greater than 20 and have some pet who like bones or toys

/[age > 20] and /pets/*/likes/[** in ["bones", "toys"]]

Here ** denotes some element in likes array.

ni is the inverse operator to in. Get documents where bones somewhere in likes array.

/pets/*/[likes ni "bones"]

We can create more complicated filters

( /[age <= 20] or /[lastName re "Do.*"] )
  and /pets/*/likes/[** in ["bones", "toys"]]

Note about grouping parentheses and regular expression matching using re operator.

Arrays and maps can be matched as is

Filter documents with likes array exactly matched to ["bones","jumping","toys"]

/**/[likes = ["bones","jumping","toys"]]

Matching algorithms for arrays and maps are different:

Array elements are fully matched from start to end. In equal arrays all values at the same index should be equal.
Object maps matching consists of the following steps:
- Lexicographically sort object keys in both maps.
- Do matching keys and its values starting from the lowest key.
- If all corresponding keys and values in one map are fully matched to ones in other and vice versa, maps considered to be equal. For example: {"f":"d","e":"j"} and {"e":"j","f":"d"} are equal maps.

Conditions on key names

Find JSON document having firstName key at root level.

/[* = "firstName"]

I this context * denotes a key name.

You can use conditions on key name and key value at the same time:

/[[* = "firstName"] = John]

Key name can be either firstName or lastName but should have John value in any case.

/[[* in ["firstName", "lastName"]] = John]

It may be useful in queries with dynamic placeholders (C API):

/[[* = :keyName] = :keyValue]

JQL data modification

APPLY section responsible for modification of documents content.

APPLY = ('apply' { PLACEHOLDER | json_object | json_array  }) | 'del'

JSON patch specs conformed to rfc7386 or rfc6902 specifications followed after apply keyword.

Let's add address object to all matched document

/[firstName=John] | apply {"address":{"city":"New York", "street":""}}

If JSON object is an argument of apply section it will be treated as merge match (rfc7386) otherwise it should be array which denotes rfc6902 JSON patch. Placegolders also supported by apply section.

/* | apply :?

Set the street name in address

/[firstName=John] | apply [{"op":"replace", "path":"/address/street", "value":"Fifth Avenue"}]

Add Neo fish to the set of John's pets

/[firstName=John]
| apply [{"op":"add", "path":"/pets/-", "value": {"name":"Neo", "kind":"fish"}}]

Removing documents

Use del keyword to remove matched elements from collection:

/FILTERS | del

Example:

> k add family {"firstName":"Jack"}
< k     2
> k query family /[firstName re "Ja.*"]
< k     2       {"firstName":"Jack"}

# Remove selected elements from collection
> k query family /[firstName=Jack] | del
< k     2       {"firstName":"Jack"}

JQL projections

PROJECTIONS = PROJECTION [ {'+' | '-'} PROJECTION ]

  PROJECTION = 'all' | json_path

Projection allow to get only subset of JSON document excluding not needed data.

Lets add one more document to our collection:

$ cat << EOF | curl -d @- -H'X-Access-Token:myaccess01' -X POST http://localhost:9191/family
{
"firstName":"Jack",
"lastName":"Parker",
"age":35,
"pets":[{"name":"Sonic", "kind":"mouse", "likes":[]}]
}
EOF

Now query only pet owners firstName and lastName from collection.

> k query family /* | /{firstName,lastName}

< k     3       {"firstName":"Jack","lastName":"Parker"}
< k     1       {"firstName":"John","lastName":"Doe"}
< k

Add pets array for every document

> k query family /* | /{firstName,lastName} + /pets

< k     3       {"firstName":"Jack","lastName":"Parker","pets":[...
< k     1       {"firstName":"John","lastName":"Doe","pets":[...

Exclude only pets field from documents

> k query family /* | all - /pets

< k     3       {"firstName":"Jack","lastName":"Parker","age":35}
< k     1       {"firstName":"John","lastName":"Doe","age":28,"address":{"city":"New York","street":"Fifth Avenue"}}
< k

Here all keyword used denoting whole document.

Get age and the first pet in pets array.

> k query family /[age > 20] | /age + /pets/0

< k     3       {"age":35,"pets":[{"name":"Sonic","kind":"mouse","likes":[]}]}
< k     1       {"age":28,"pets":[{"name":"Rexy rex","kind":"dog","likes":["bones","jumping","toys"]}]}
< k

JQL sorting

  ORDERBY = ({ 'asc' | 'desc' } PLACEHOLDER | json_path)...

Lets add one more document then sort documents in collection by firstName ascending and age descending.

> k add family {"firstName":"John", "lastName":"Ryan", "age":39}
< k     4

> k query family /* | /{firstName,lastName,age} | asc /firstName desc /age
< k     3       {"firstName":"Jack","lastName":"Parker","age":35}
< k     4       {"firstName":"John","lastName":"Ryan","age":39}
< k     1       {"firstName":"John","lastName":"Doe","age":28}
< k

asc, desc instructions may use indexes defined for collection to avoid a separate documents sorting stage.

JQL Options

OPTS = { 'skip' n | 'limit' n | 'count' | 'noidx' | ORDERBY }...

skip n Skip first n records before first element in result set
limit n Set max number of documents in result set

count Returns only count of matched documents

> k query family /* | count
< k     3
< k

noidx Do not use any indexes for query execution.

JQL Indexing and performance tips

Database index can be build for any JSON field path of number or string type. Index can be an unique ‐ not allowing indexed values duplication and non unique. The following index mode bit mask flags are used (defined in ejdb2.h):

Index mode	Description
`0x01 EJDB_IDX_UNIQUE`	Index is unique
`0x04 EJDB_IDX_STR`	Index for JSON `string` field value type
`0x08 EJDB_IDX_I64`	Index for `8 bytes width` signed integer field values
`0x10 EJDB_IDX_F64`	Index for `8 bytes width` signed floating point field values.

For example mode specifies unique index of string type will be EJDB_IDX_UNIQUE | EJDB_IDX_STR = 0x05. Index creation operation may define index for only one type.

Lets define non unique string index for /lastName path:

> k idx family 4 /lastName
< k

Index selection for queries based on set of heuristic rules.

You can always check index usage by issuing explain command in WS API:

> k explain family /[lastName=Doe] and /[age!=27]
< k     explain [INDEX] MATCHED  STR|3 /lastName EXPR1: 'lastName = Doe' INIT: IWKV_CURSOR_EQ
[INDEX] SELECTED STR|3 /lastName EXPR1: 'lastName = Doe' INIT: IWKV_CURSOR_EQ
 [COLLECTOR] PLAIN

The following statements are taken into account when using EJDB2 indexes:

Only one index can be used for particular query

If query consist of or joined parts or contains negated at top level indexes will not be used. No indexes below:

/[lastName != Andy]

/[lastName = "John"] or /[lastName = Peter]

Will use /lastName defined above

/[lastName = Doe]

/[lastName = Doe] and /[age = 28]

/[lastName = Doe] and /[age != 28]

The ony following operators are supported by indexes (ejdb 2.0.x):
- eq, =
- gt, >
- gte, >=
- lt, <
- lte, <=
- in
ORDERBY clauses may use indexes to avoid result set sorting

Array fields can also be indexed. Let's outline a typical use case: indexing of some entity tags:

> k add books {"name":"Mastering Ultra", "tags":["ultra", "language", "bestseller"]}
< k     1
> k add books {"name":"Learn something in 24 hours", "tags":["bestseller"]}
< k     2
> k query books /*
< k     2       {"name":"Learn something in 24 hours","tags":["bestseller"]}
< k     1       {"name":"Mastering Ultra","tags":["ultra","language","bestseller"]}
< k

Create string index for /tags

> k idx books 4 /tags
< k

Filter books by bestseller tag and show index usage in query:

> k explain books /tags/[** in ["bestseller"]]
< k     explain [INDEX] MATCHED  STR|4 /tags EXPR1: '** in ["bestseller"]' INIT: IWKV_CURSOR_EQ
[INDEX] SELECTED STR|4 /tags EXPR1: '** in ["bestseller"]' INIT: IWKV_CURSOR_EQ
[COLLECTOR] PLAIN

< k     1       {"name":"Mastering Ultra","tags":["ultra","language","bestseller"]}
< k     2       {"name":"Learn something in 24 hours","tags":["bestseller"]}
< k

NOTE: In many cases, using index may drop down the overall query performance. Because index collection contains only document references (id) and engine may perform an addition document fetching by its primary key to finish query matching. So for not so large collections a brute scan may perform better than scan using indexes.

However, exact matching operations: eq, in and sorting by natural index order will always benefit from index in any case.

HTTP REST/Websocket API endpoint

EJDB engine provides the ability to start a separate HTTP/Websocket endpoint worker exposing network API for quering and data modifications.

The easiest way to expose database over the network is using the standalone jbs server. (Of course if you plan to avoid C API integration).

jbs server

jbs -h

EJDB 2.0.0 standalone REST/Websocket server. http://ejdb.org

 --file <>	Database file path. Default: db.jb
 -f <>    	(same as --file)
 --port ##	HTTP port number listen to. Default: 9191
 -p ##    	(same as --port)
 --bind <>	Address server listen. Default: localhost
 -b <>    	(same as --bind)
 --access <>	Server access token matched to 'X-Access-Token' HTTP header value
 -a <>      	(same as --access)
 --trunc   	Cleanup existing database file on open
 -t        	(same as --trunc)
 --wal   	Use write ahead logging (WAL). Must be set for data durability.
 -w      	(same as --wal)

Advanced options
 --sbz ##	Max sorting buffer size. If exeeded, an overflow temp file for data will created. Default: 16777216, min: 1048576
 --dsz ##	Initial size of buffer to process/store document on queries. Preferable average size of document. Default: 65536, min: 16384
 --bsz ##	Max HTTP/WS API document body size. Default: 67108864, min: 524288

Use any of the following input formats:
	-arg <value>	-arg=<value>	-arg<value>

Use the -h, -help or -? to get this information again.

HTTP API

Access to HTTP endpoint can be protected by a token specified with --access command flag or by C API EJDB_HTTP options. If access token specified on server, a client should provide X-Access-Token HTTP header value. If token is required and not provided by client 401 HTTP code will be returned. If access token is required and not matched to the token provided by client 403 HTTP code will returned. In any error case 500 error will be returned.

REST API

POST /{collection}

Add a new document to the collection.

200 success. Body: a new document identifier as int64 number

PUT /{collection}/{id}

Replaces/store document under specific numeric id

200 on success. Empty body

DELETE /{collection}/{id}

Removes document identified by id from a collection

200 on success. Empty body
404 if document not found

PATCH /{collection}/{id}

Patch a document identified by id by rfc7396, rfc6902 data.

200 on success. Empty body

GET | HEAD /{collections}/{id}

Retrieve document identified by id from a collection.

200 on success. Body: JSON document text.
- content-type:application/json
- content-length:
404 if document not found

POST /

Query a collection by provided query as POST body. Body of query should contains collection name in use in the first filter element: @collection_name/... Request headers:

X-Hints comma separated extra hints to ejdb2 database engine.
- explain Show query execution plan before first element in result set separated by -------------------- line. Response:
Response data transfered using HTTP chunked transfer encoding
200 on success.
JSON documents separated by \n in the following format:
```
\r\n<document id>\t<document JSON body>
...
```

Example:

curl -v --data-raw '@family/[age > 18]' -H 'X-Access-Token:myaccess01' http://localhost:9191
* Rebuilt URL to: http://localhost:9191/
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 9191 (#0)
> POST / HTTP/1.1
> Host: localhost:9191
> User-Agent: curl/7.58.0
> Accept: */*
> X-Access-Token:myaccess01
> Content-Length: 18
> Content-Type: application/x-www-form-urlencoded
>
* upload completely sent off: 18 out of 18 bytes
< HTTP/1.1 200 OK
< connection:keep-alive
< content-type:application/json
< transfer-encoding:chunked
<

4	{"firstName":"John","lastName":"Ryan","age":39}
3	{"firstName":"Jack","lastName":"Parker","age":35,"pets":[{"name":"Sonic","kind":"mouse","likes":[]}]}
1	{"firstName":"John","lastName":"Doe","age":28,"pets":[{"name":"Rexy rex","kind":"dog","likes":["bones","jumping","toys"]},{"name":"Grenny","kind":"parrot","likes":["green color","night","toys"]}],"address":{"city":"New York","street":"Fifth Avenue"}}
* Connection #0 to host localhost left intact

curl --data-raw '@family/[lastName = "Ryan"]' -H 'X-Access-Token:myaccess01' -H 'X-Hints:explain' http://localhost:9191
[INDEX] MATCHED  STR|3 /lastName EXPR1: 'lastName = "Ryan"' INIT: IWKV_CURSOR_EQ
[INDEX] SELECTED STR|3 /lastName EXPR1: 'lastName = "Ryan"' INIT: IWKV_CURSOR_EQ
 [COLLECTOR] PLAIN
--------------------
4	{"firstName":"John","lastName":"Ryan","age":39}

OPTIONS /

Fetch ejdb JSON metadata and available HTTP methods in Allow response header. Example:

curl -X OPTIONS -H 'X-Access-Token:myaccess01'  http://localhost:9191/
{
 "version": "2.0.0",
 "file": "db.jb",
 "size": 16384,
 "collections": [
  {
   "name": "family",
   "dbid": 3,
   "rnum": 3,
   "indexes": [
    {
     "ptr": "/lastName",
     "mode": 4,
     "idbf": 64,
     "dbid": 4,
     "rnum": 3
    }
   ]
  }
 ]
}

Websocket API

EJDB supports simple text based protocol over HTTP websocket protocol. You can use interactive websocket CLI tool wscat to communicate with server by hands.

Commands

?

Will respond with the following help text message:

wscat  -H 'X-Access-Token:myaccess01' -q -c http://localhost:9191
> ?
<
<key> info
<key> get     <collection> <id>
<key> set     <collection> <id> <document json>
<key> add     <collection> <document json>
<key> del     <collection> <id>
<key> patch   <collection> <id> <patch json>
<key> idx     <collection> <mode> <path>
<key> rmi     <collection> <mode> <path>
<key> rmc     <collection>
<key> query   <collection> <query>
<key> explain <collection> <query>
<key> <query>
>

Note about <key> prefix before every command; It is an arbitrary key choosen by client and designated to identify particular websocket request, this key will be returned with response to request and allows client to identify that response for his particular request.

Errors are returned in the following format:

<key> ERROR: <error description>

`<key> info`

Get database metadatas as JSON document.

`<key> get <collection> <id>`

Retrieve document identified by id from a collection. If document is not found IWKV_ERROR_NOTFOUND will be returned.

Example:

> k get family 3
< k     3       {
 "firstName": "Jack",
 "lastName": "Parker",
 "age": 35,
 "pets": [
  {
   "name": "Sonic",
   "kind": "mouse",
   "likes": []
  }
 ]
}

If document not found we will get error:

> k get family 55
< k ERROR: Key not found. (IWKV_ERROR_NOTFOUND)
>

`<key> set <collection> <id> <document json>`

Replaces/add document under specific numeric id. Collection will be created automatically if not exists.

`<key> add <collection> <document json>`

Add new document to <collection> New id of document will be generated and returned as response. `Collection> will be created automatically if not exists.

Example:

> k add mycollection {"foo":"bar"}
< k     1
> k add mycollection {"foo":"bar"}
< k     2
>

`<key> del <collection> <id>`

Remove document identified by id from the collection. If document is not found IWKV_ERROR_NOTFOUND will be returned.

`<key> patch <collection> <id> <patch json>`

Apply rfc7396 or rfc6902 patch to the document identified by id. If document is not found IWKV_ERROR_NOTFOUND will be returned.

`<key> query <collection> <query>`

Execute query on documents in specified collection. Response: A set of WS messages with document boidies terminated by the last message with empty body.

> k query family /* | /firstName
< k     4       {"firstName":"John"}
< k     3       {"firstName":"Jack"}
< k     1       {"firstName":"John"}
< k

Note about last message: <key> with no body.

`<key> explain <collection> <query>`

Same as <key> query <collection> <query> but the first response message will be prefixed by <key> explain and contains query execution plan.

Example:

> k explain family /* | /firstName
< k     explain [INDEX] NO [COLLECTOR] PLAIN

< k     4       {"firstName":"John"}
< k     3       {"firstName":"Jack"}
< k     1       {"firstName":"John"}
< k

Execute query text. Body of query should contains collection name in use in the first filter element: @collection_name/.... Behaviour is the same as for: <key> query <collection> <query>

`<key> idx <collection> <mode> <path>`

Ensure index with specified mode (bitmask flag) for given json path and collection. Collection will be created if not exists.

Index mode	Description
`0x01 EJDB_IDX_UNIQUE`	Index is unique
`0x04 EJDB_IDX_STR`	Index for JSON `string` field value type
`0x08 EJDB_IDX_I64`	Index for `8 bytes width` signed integer field values
`0x10 EJDB_IDX_F64`	Index for `8 bytes width` signed floating point field values.

Example:

k idx mycollection 5 /name

`<key> rmi <collection> <mode> <path>`

Remove index with specified mode (bitmask flag) for given json path and collection. Return error if given index not found.

`<key> rmc <collection>`

Remove collection and all of its data. Note: If collection is not found no errors will be reported.

C API

EJDB can be empdedded into any C/C++ application. C API documented in the following headers:

ejdb.h Main API functions
jbl.h JSON documents management API
jql.h Query building API

Example application:

#include <ejdb2/ejdb2.h>

#define RCHECK(rc_)          \
  if (rc_) {                 \
    iwlog_ecode_error3(rc_); \
    return 1;                \
  }

static iwrc documents_visitor(EJDB_EXEC *ctx, const EJDB_DOC doc, int64_t *step) {
  // Print document to stderr
  return jbl_as_json(doc->raw, jbl_fstream_json_printer, stderr, JBL_PRINT_PRETTY);
}

int main() {

  EJDB_OPTS opts = {
    .kv = {
      .path = "example.db",
      .oflags = IWKV_TRUNC
    }
  };
  EJDB db;     // EJDB2 storage handle
  int64_t id;  // Document id placeholder
  JQL q = 0;   // Query instance
  JBL jbl = 0; // Json document

  iwrc rc = ejdb_init();
  RCHECK(rc);

  rc = ejdb_open(&opts, &db);
  RCHECK(rc);

  // First record
  rc = jbl_from_json(&jbl, "{\"name\":\"Bianca\", \"age\":4}");
  RCGO(rc, finish);
  rc = ejdb_put_new(db, "parrots", jbl, &id);
  RCGO(rc, finish);
  jbl_destroy(&jbl);

  // Second record
  rc = jbl_from_json(&jbl, "{\"name\":\"Darko\", \"age\":8}");
  RCGO(rc, finish);
  rc = ejdb_put_new(db, "parrots", jbl, &id);
  RCGO(rc, finish);
  jbl_destroy(&jbl);

  // Now execute a query
  rc =  jql_create(&q, "parrots", "/[age > :age]");
  RCGO(rc, finish);

  EJDB_EXEC ux = {
    .db = db,
    .q = q,
    .visitor = documents_visitor
  };

  // Set query placeholder value.
  // Actual query will be /[age > 3]
  rc = jql_set_i64(q, "age", 0, 3);
  RCGO(rc, finish);

  // Now execute the query
  rc = ejdb_exec(&ux);

finish:
  if (q) jql_destroy(&q);
  if (jbl) jbl_destroy(&jbl);
  ejdb_close(&db);
  RCHECK(rc);
  return 0;
}

Compile and run:

gcc -std=gnu11 -Wall -pedantic -c -o example1.o example1.c
gcc -o example1 example1.o -lejdb2

./example1
{
 "name": "Darko",
 "age": 8
}{
 "name": "Bianca",
 "age": 4
}

License


MIT License

Copyright (c) 2012-2019 Softmotions Ltd <info@softmotions.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Files

README.md

Latest commit

History

README.md

File metadata and controls

EJDB 2.0

Native language bindings

Status

Supported platforms

OSX

Linux

Ubuntu/Debian

PPA repository

Building debian packages

RPM based Linux distributions

Android

Android binding showcase and unit tests

JQL

JQL grammar

Non formal JQL grammar adapted for brief overview

JQL quick introduction

Get all elements in collection

Set the maximum number of elements in result set

Get documents where specified json path exists

Matching JSON entry values

Arrays and maps can be matched as is

Conditions on key names

JQL data modification

Removing documents

JQL projections

JQL sorting

JQL Options

JQL Indexing and performance tips

HTTP REST/Websocket API endpoint

jbs server

HTTP API

REST API

POST /{collection}

PUT /{collection}/{id}

DELETE /{collection}/{id}

PATCH /{collection}/{id}

GET | HEAD /{collections}/{id}

POST /

OPTIONS /

Websocket API

Commands

?

<key> info

<key> get <collection> <id>

<key> set <collection> <id> <document json>

<key> add <collection> <document json>

<key> del <collection> <id>

<key> patch <collection> <id> <patch json>

<key> query <collection> <query>

<key> explain <collection> <query>

<key> idx <collection> <mode> <path>

<key> rmi <collection> <mode> <path>

<key> rmc <collection>

C API

License

`<key> info`

`<key> get <collection> <id>`

`<key> set <collection> <id> <document json>`

`<key> add <collection> <document json>`

`<key> del <collection> <id>`

`<key> patch <collection> <id> <patch json>`

`<key> query <collection> <query>`

`<key> explain <collection> <query>`

`<key> idx <collection> <mode> <path>`

`<key> rmi <collection> <mode> <path>`

`<key> rmc <collection>`