Crate SQL HTTP Endpoint — Crate documentation

sh$ curl -sSXPOST '127.0.0.1:4200/_sql?pretty' -d '{
... "stmt":"select name, position from locations order by id limit 2"
... }'
{
  "cols" : [ "name", "position" ],
  "duration" : ...,
  "rows" : [ [ "North West Ripple", 1 ], [ "Arkintoofle Minor", 3 ] ],
  "rowcount" : 2
}

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 bei 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 -sSXPOST '127.0.0.1:4200/_sql?pretty' -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" ],
  "duration" : ...,
  "rows" : [ [ 308534400000, 1 ], [ 308534400000, 2 ] ],
  "rowcount" : 2
}

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

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

Column Types¶

Crate 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 -sSXPOST '127.0.0.1:4200/_sql?types&pretty' -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 ],
  "duration" : ...,
  "rows" : [ [ 308534400000, 1 ], [ 308534400000, 2 ] ],
  "rowcount" : 2
}

Collection data types like Set or Array are displayed as a list where the first value is the collection type and the second is the inner type. Of course the inner type could also be a collection.

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

"column_types": [ 4, [ 101, [ 100, 9 ] ] ]

Id’s of all currently available data types:

Id	Data Type
0	Null
1	Not Supported
2	Byte
3	Boolean
4	String
5	Ip
6	Double
7	Float
8	Short
9	Integer
10	Long
11	Timestamp
12	Object
13	GeoPoint (Double[])
100	Array
101	Set

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 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 -sSXPOST '127.0.0.1:4200/_sql?pretty' -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
  } ]
<BLANKLINE>
}

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 -sSXPOST '127.0.0.1:4200/_sql?pretty' -d '{
... "stmt":"select name, position"
... }'
{
  "error" : {
    "message" : "SQLActionException[FROM clause is missing.]",
    "code" : 4000
  }
}

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 -sSXPOST '127.0.0.1:4200/_sql?pretty&error_trace=True' -d '{
... "stmt":"select name, position"
... }'
{
  "error" : {
    "message" : "SQLActionException[FROM clause is missing.]",
    "code" : 4000
  },
  "error_trace" : "..."
}

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 table 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.
4041	Unknown table.
4042	Unknown analyzer.
4043	Unknown column.
4044	Unknown type.
4045	Unknown schema.
4046	Unknown Partition.
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 table with the same name exists already.
4094	The used table alias contains tables with different schema.
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

sh$ curl -sSXPOST '127.0.0.1:4200/_sql?pretty' -d@- <<- EOF
... {"stmt": "INSERT into locations (name, id) values (?,?)",
... "bulk_args": [
...     ["Mars", 1341],
...     ["Sun", 1341]
... ]
... }
... EOF
{
  "cols" : [ ],
  "duration" : ...,
  "results" : [ {
    "rowcount" : 1
  }, {
    "rowcount" : -2
  } ]
}