HTTP endpoint

Table of contents

Introduction

CrateDB provides a HTTP Endpoint that can be used to submit SQL queries. The endpoint is accessible under <servername:port>/_sql.

SQL statements are sent to the _sql endpoint in json format, whereby the statement is sent as value associated to the key stmt.

A simple SELECT statement can be submitted like this:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql' \
... -d '{"stmt":"select name, position from locations order by id limit 2"}'
{
  "cols": [
    "name",
    "position"
  ],
  "rows": [
    [
      "North West Ripple",
      1
    ],
    [
      "Outer Eastern Rim",
      2
    ]
  ],
  "rowcount": 2,
  "duration": ...
}

Note

We’re using a simple command line invokation of curl here so you can see how to run this by hand in the terminal. For the rest of the examples in this document, we use here documents (i.e. EOF) for multiline readability.

Parameter substitution

In addition to the stmt key the request body may also contain an args key which can be used for SQL parameter substitution.

The SQL statement has to be changed to use placeholders where the values should be inserted. Placeholders can either be numbered (in the form of $1, $2, etc.) or unnumbered using a question mark ?.

The placeholders will then be substituted with values from an array that is expected under the args key:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql' -d@- <<- EOF
... {
...   "stmt":
...     "select date,position from locations
...     where date <= \$1 and position < \$2 order by position",
...   "args": ["1979-10-12", 3]
... }
... EOF
{
  "cols": [
    "date",
    "position"
  ],
  "rows": [
    [
      308534400000,
      1
    ],
    [
      308534400000,
      2
    ]
  ],
  "rowcount": 2,
  "duration": ...
}

Note

In this example the placeholders start with an backslash due to shell escaping.

Warning

Parameter substitution must not be used within subscript notation.

For example, column[?] is not allowed.

The same query using question marks as placeholders looks like this:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql' -d@- <<- EOF
... {
...   "stmt":
...     "select date,position from locations
...     where date <= ? and position < ? order by position",
...   "args": ["1979-10-12", 3]
... }
... EOF
{
  "cols": [
    "date",
    "position"
  ],
  "rows": [
    [
      308534400000,
      1
    ],
    [
      308534400000,
      2
    ]
  ],
  "rowcount": 2,
  "duration": ...
}

Note

With some queries the row count is not ascertainable. In this cases rowcount is -1.

Default schema

It is possible to set a default schema while querying the CrateDB cluster via _sql end point. In such case the HTTP request should contain the Default-Schema header with the specified schema name:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql' \
... -H 'Default-Schema: doc' -d@- <<- EOF
... {
...   "stmt":"select name, position from locations order by id limit 2"
... }
... EOF
{
  "cols": [
    "name",
    "position"
  ],
  "rows": [
    [
      "North West Ripple",
      1
    ],
    [
      "Outer Eastern Rim",
      2
    ]
  ],
  "rowcount": 2,
  "duration": ...
}

If the schema name is not specified in the header, the default doc schema will be used instead.

Column types

CrateDB can respond a list col_types with the data type ID of every responded column. This way one can know what exact data type a column is holding.

In order to get the list of column data types, a types query parameter must be passed to the request:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql?types' -d@- <<- EOF
... {
...   "stmt":
...     "select date, position from locations
...      where date <= \$1 and position < \$2 order by position",
...   "args": ["1979-10-12", 3]
... }
... EOF
{
  "cols": [
    "date",
    "position"
  ],
  "col_types": [
    11,
    9
  ],
  "rows": [
    [
      308534400000,
      1
    ],
    [
      308534400000,
      2
    ]
  ],
  "rowcount": 2,
  "duration": ...
}

The Array collection data type is displayed as a list where the first value is the collection type and the second is the inner type. The inner type could also be a collection.

Example of JSON representation of a column list of (String, Integer[]):

"column_types": [ 4, [ 100, 9 ] ]

IDs of all currently available data types:

ID

Data Type

Format

0

Null

null

1

Not Supported

2

char

single byte

3

boolean

true or false

4

text

all unicode characters allowed

5

ip

‘0:0:0:0:0:ffff:c0a8:64’, ‘192.169.0.55’

6

double precision

15 decimal digits precision

7

real

6 decimal digits precision

8

smallint

range -32768 to 32767

9

integer

range -2^31 to 2^31-1

10

bigint

range -2^63 to 2^63-1

11

timestamp

bigint e.g. 1591808274761

12

object(dynamic|strict|ignored)

‘{“key”: “value”}’, { key = ‘value’}

13

geo_point

[lon_value::double, lat_value::double] e.g. [28.979999972507358,-57.33000000938773]

14

geo_shape

object[] e.g. [{“coordinates”:[[[100.0,0.0],[101.0,0.0],[101.0,1.0]]],”type”:”Polygon”}]

15

Unchecked Object

19

regproc

20

time with time zone

[bigint, integer] e.g. [70652987666, 0]

21

oidvector

An array of numbers

23

regclass

OID, referring the OID of the pg_class table. The result is an INTEGER.

24

date

range 292275054BC to 292278993AD

100

array

[integer, integer] e.g. [100, 9] for a array(integer)

Bulk operations

The REST endpoint allows to issue bulk operations which are executed as single calls on the back-end site. It can be compared to prepared statement.

A bulk operation can be expressed simply as an SQL statement.

Supported bulk SQL statements are:

  • Insert

  • Update

  • Delete

Instead of the args (Parameter substitution) key, use the key bulk_args. This allows to specify a list of lists, containing all the records which shall be processed. The inner lists need to match the specified columns.

The bulk response contains a results array, with a rowcount for each bulk operation. Those results are in the same order as the issued operations of the bulk operation.

The following example describes how to issue an insert bulk operation and insert three records at once:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql' -d@- <<- EOF
... {
...   "stmt": "INSERT INTO locations (id, name, kind, description)
...           VALUES (?, ?, ?, ?)",
...   "bulk_args": [
...     [1337, "Earth", "Planet", "An awesome place to spend some time on."],
...     [1338, "Sun", "Star", "An extraordinarily hot place."],
...     [1339, "Titan", "Moon", "Titan, where it rains fossil fuels."]
...   ]
... }
... EOF
{
  "cols": [],
  "duration": ...,
  "results": [
    {
      "rowcount": 1
    },
    {
      "rowcount": 1
    },
    {
      "rowcount": 1
    }
  ]
}

Error handling

Queries that are invalid or cannot be satisfied will result in an error response. The response will contain an error code, an error message and in some cases additional arguments that are specific to the error code.

Client libraries should use the error code to translate the error into an appropriate exception:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql' -d@- <<- EOF
... {
...   "stmt":"select name, position from foo.locations"
... }
... EOF
{
  "error": {
    "message": "SchemaUnknownException[Schema 'foo' unknown]",
    "code": 4045
  }
}

To get more insight into what exactly went wrong an additional error_trace GET parameter can be specified to return the stack trace:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql?error_trace=true' -d@- <<- EOF
... {
...   "stmt":"select name, position from foo.locations"
... }
... EOF
{
  "error": {
    "message": "SchemaUnknownException[Schema 'foo' unknown]",
    "code": 4045
  },
  "error_trace": "..."
}

Note

This parameter is intended for CrateDB developers or for users requesting support for CrateDB. Client libraries shouldn’t make use of this option and not include the stacktrace.

Currently the defined error codes are:

Code

Error

4000

The statement contains an invalid syntax or unsupported SQL statement

4001

The statement contains an invalid analyzer definition.

4002

The name of the relation is invalid.

4003

Field type validation failed

4004

Possible feature not supported (yet)

4005

Alter table using a table alias is not supported.

4006

The used column alias is ambiguous.

4007

The operation is not supported on this relation, as it is not accessible.

4008

The name of the column is invalid.

4009

CrateDB License is expired. (Deprecated.)

4010

User is not authorized to perform the SQL statement.

4011

Missing privilege for user.

4031

Only read operations are allowed on this node.

4041

Unknown relation.

4042

Unknown analyzer.

4043

Unknown column.

4044

Unknown type.

4045

Unknown schema.

4046

Unknown Partition.

4047

Unknown Repository.

4048

Unknown Snapshot.

4049

Unknown user-defined function.

40410

Unknown user.

4091

A document with the same primary key exists already.

4092

A VersionConflict. Might be thrown if an attempt was made to update the same document concurrently.

4093

A relation with the same name exists already.

4094

The used table alias contains tables with different schema.

4095

A repository with the same name exists already.

4096

A snapshot with the same name already exists in the repository.

4097

A partition for the same values already exists in this table.

4098

A user-defined function with the same signature already exists.

4099

A user with the same name already exists.

5000

Unhandled server error.

5001

The execution of one or more tasks failed.

5002

One or more shards are not available.

5003

The query failed on one or more shards

5004

Creating a snapshot failed

5030

The query was killed by a kill statement

Bulk errors

If a bulk operation fails, the resulting rowcount will be -2 and the resulting object may contain an error_message depending on the resulting error:

sh$ curl -sS -H 'Content-Type: application/json' \
... -X POST '127.0.0.1:4200/_sql' -d@- <<- EOF
... {
...   "stmt": "INSERT into locations (name, id) values (?,?)",
...   "bulk_args": [
...     ["Mars", 1341],
...     ["Sun", 1341]
...   ]
... }
... EOF
{
  "cols": [],
  "duration": ...,
  "results": [
    {
      "rowcount": 1
    },
    {
      "rowcount": -2
    }
  ]
}

Note

Every bulk operation will be executed, independent if one of the operation fails.

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