Returns the result of a query as a Hive primitive value. Each Hive primitive data type has a separate function named for it:
xml_query_as_string
xml_query_as_boolean
xml_query_as_tinyint
xml_query_as_smallint
xml_query_as_int
xml_query_as_bigint
xml_query_as_double
xml_query_as_float
An XQuery or XPath expression. It must be a constant value, because it is only read the first time the function is evaluated. The initial query string is compiled and reused in all subsequent calls.
You can access files that are stored in the Hadoop distributed cache and HTTP resources (http://...
). Use the XQuery fn:doc
function for XML documents, and the fn:unparsed-text
and fn:parsed-text-lines
functions to access plain text files. See Example 4.
If an error occurs while compiling the query, the function raises an error. If an error occurs while evaluating the query, the error is logged (not raised), and an empty array is returned.
The input that the query processes. The value can be an XML STRING
or a STRUCT
of variable values:
STRING
: The string is bound to the initial context item of the query as XML. See Example 1.
STRUCT
: A STRUCT
with an even number of fields. Each pair of fields defines a variable binding (name, value) for the query. The name fields must be type STRING
, and the value fields can be any supported primitive. See "Data Type Conversions" and Example 2.
The first item in the result of the query is cast to the XML schema type that maps to the primitive type of the function. If the query returns multiple items, then all but the first are ignored.
A Hive primitive value, which is the first item returned by the query, converted to an atomic value. If the result of the query is empty, then the return value is NULL
.
This example parses and binds the input XML string to the initial context item of the query x/y
:
hive> SELECT xml_query_as_string("x/y", "<x><y>hello</y></x>") FROM src LIMIT 1;
.
.
.
"hello"
The following are string binding examples that use other primitive functions:
hive> SELECT xml_query_as_int("x/y", "<x><y>123</y></x>") FROM src LIMIT 1; . . . 123 hive> SELECT xml_query_as_double("x/y", "<x><y>12.3</y></x>") FROM src LIMIT 1; . . . 12.3 hive> SELECT xml_query_as_boolean("x/y", "<x><y>true</y></x>") FROM src LIMIT 1; . . . true
In this example, the second argument is a STRUCT
that defines two query variables, $data
and $value
. The values of the variables in the STRUCT
are converted to XML schema types as described in "Data Type Conversions."
hive> SELECT xml_query_as_string( "fn:parse-xml($data)/x/y[@id = $value]", struct( "data", "<x><y id='1'>hello</y><z/><y id='2'>world</y></x>", "value", 2 ) ) FROM src LIMIT 1; . . . world
This example returns only the first item (hello) from the query. The second item (world) is discarded.
hive> SELECT xml_query_as_string("x/y", "<x><y>hello</y><z/><y>world</y></x>") FROM src LIMIT 1;
.
.
.
hello
This example returns NULL
because the result of the query is empty:
hive> SELECT xml_query_as_string("x/foo", "<x><y>hello</y><z/><y>world</y></x>") FROM src LIMIT 1;
.
.
.
NULL
These examples use the fn:serialize
function to return complex XML elements as a STRING
value:
hive> SELECT xml_query_as_string("fn:serialize(x/y[1])", "<x><y>hello</y><z/><y>world</y></x>") FROM src LIMIT 1; . . . "<y>hello</y>" hive> SELECT xml_query_as_string( "fn:serialize(<html><head><title>{$desc}</title></head><body>Name: {$name}</body></html>)", struct( "desc", "Employee Details", "name", "John Doe" ) ) FROM src LIMIT 1; ... <html><head><title>Employee Details</title></head><body>Name: John Doe</body></html>
This example adds a file named test.xml
to the distributed cache, and then queries it using the fn:doc
function. The file contains this value:
<x><y>hello</y><z/><y>world</y></x>
Hive> ADD FILE test.xml; Added resource: test.xml Hive> SELECT xml_query_as_string("fn:doc('test.xml')/x/y[1]", NULL) FROM src LIMIT 1; . . . hello
This example returns NULL
because </invalid
is missing an angle bracket. An XML parsing error is written to the log:
Hive> SELECT xml_query_as_string("x/y", "<x><y>hello</invalid") FROM src LIMIT 1;
.
.
.
NULL
This example returns NULL
because foo
cannot be cast as xs:float
. A cast error is written to the log:
Hive> SELECT xml_query_as_float("x/y", "<x><y>foo</y></x>") FROM src LIMIT 1;
.
.
.
NULL