EXPLODE
Expands one or more columns in a collection (ARRAY or SET) into individual table rows, one row per element, with any other columns specified in the query. For each exploded collection, the results include two columns, one for the element index, and one for the value at that position. If the function explodes a single collection, these columns are named position and value by default. If the function explodes two or more collections, the columns for each collection are named pos_column-name and val_column-name. You can use an AS clause in the SELECT to change these column names.
This function requires an OVER() clause.
Behavior Type
Syntax
EXPLODE (column[,...] [USING PARAMETERS explode_count=number_of_arrays_to_explode]) OVER ( [window-partition-clause] )
Arguments
| column | Column in the table being queried. You must specify at least as many collection columns as the value of the explode_count parameter. Columns that are not collections are passed through without modification. |
Parameters
explode_count
|
The number of collection columns to explode (default 1). The function checks each column, up to this value, and either explodes it if is a collection or passes it through if it is not a collection or if this limit has been reached. If the value of explode_count is greater than the number of collection columns specified, the function returns an error. |
Supported Data Types
Columns to be exploded must be arrays or sets of any element type.
Other columns may be of any type.
Null-Handling
This function expands each element in a collection into a row, including nulls. If the column to be exploded is NULL (not empty), the function produces no rows for that collection.
Examples
The following examples illustrate using EXPLODE() with the OVER(PARTITION BEST) clause.
Consider an orders table with columns for order keys, customer keys, product keys, order prices, and email addresses, with some containing arrays. A basic query in Vertica results in the following:
=> SELECT orderkey, custkey, prodkey, orderprices, email_addrs FROM orders LIMIT 5; orderkey | custkey | prodkey | orderprices | email_addrs ------------+---------+-----------------------------------------------+-----------------------------------+---------------------------------------------------------------------------------------------------------------- 113-341987 | 342799 | ["MG-7190 ","VA-4028 ","EH-1247 ","MS-7018 "] | ["60.00","67.00","22.00","14.99"] | ["bob@example,com","robert.jones@example.com"] 111-952000 | 342845 | ["ID-2586 ","IC-9010 ","MH-2401 ","JC-1905 "] | ["22.00","35.00",null,"12.00"] | ["br92@cs.example.edu"] 111-345634 | 342536 | ["RS-0731 ","SJ-2021 "] | ["50.00",null] | [null] 113-965086 | 342176 | ["GW-1808 "] | ["108.00"] | ["joe.smith@example.com"] 111-335121 | 342321 | ["TF-3556 "] | ["50.00"] | ["789123@example-isp.com","alexjohnson@example.com","monica@eng.example.com","sara@johnson.example.name",null] (5 rows)
This example expands the orderprices column for a specified customer, in ascending order. The custkey and email_addrs columns are repeated for each array element.
=> SELECT EXPLODE(orderprices, custkey, email_addrs) OVER(PARTITION BEST) AS (position, orderprices, custkey, email_addrs)
FROM orders WHERE custkey='342845' ORDER BY orderprices;
position | orderprices | custkey | email_addrs
----------+-------------+---------+------------------------------
2 | | 342845 | ["br92@cs.example.edu",null]
3 | 12.00 | 342845 | ["br92@cs.example.edu",null]
0 | 22.00 | 342845 | ["br92@cs.example.edu",null]
1 | 35.00 | 342845 | ["br92@cs.example.edu",null]
(4 rows)
When you explode a column that contains null values, the null values are displayed as empty.
You can explode more than one column by specifying the explode_count parameter.
=> SELECT EXPLODE(orderkey, prodkey, orderprices USING PARAMETERS explode_count=2) OVER(PARTITION BEST) AS (orderkey,pk_idx,pk_val,ord_idx,ord_val) FROM orders WHERE orderkey='113-341987'; orderkey | pk_idx | pk_val | ord_idx | ord_val ------------+--------+----------+---------+--------- 113-341987 | 0 | MG-7190 | 0 | 60.00 113-341987 | 0 | MG-7190 | 1 | 67.00 113-341987 | 0 | MG-7190 | 2 | 22.00 113-341987 | 0 | MG-7190 | 3 | 14.99 113-341987 | 1 | VA-4028 | 0 | 60.00 113-341987 | 1 | VA-4028 | 1 | 67.00 113-341987 | 1 | VA-4028 | 2 | 22.00 113-341987 | 1 | VA-4028 | 3 | 14.99 113-341987 | 2 | EH-1247 | 0 | 60.00 113-341987 | 2 | EH-1247 | 1 | 67.00 113-341987 | 2 | EH-1247 | 2 | 22.00 113-341987 | 2 | EH-1247 | 3 | 14.99 113-341987 | 3 | MS-7018 | 0 | 60.00 113-341987 | 3 | MS-7018 | 1 | 67.00 113-341987 | 3 | MS-7018 | 2 | 22.00 113-341987 | 3 | MS-7018 | 3 | 14.99 (16 rows)
The following example uses a multi-dimensional array:
=> SELECT name, pingtimes FROM network_tests; name | pingtimes ------+------------------------------------------------------- eng1 | [[24.24,25.27,27.16,24.97],[23.97,25.01,28.12,29.5]] eng2 | [[27.12,27.91,28.11,26.95],[29.01,28.99,30.11,31.56]] qa1 | [[23.15,25.11,24.63,23.91],[22.85,22.86,23.91,31.52]] (3 rows) => SELECT EXPLODE(name, pingtimes USING PARAMETERS explode_count=1) OVER() FROM network_tests; name | position | value ------+----------+--------------------------- eng1 | 0 | [24.24,25.27,27.16,24.97] eng1 | 1 | [23.97,25.01,28.12,29.5] eng2 | 0 | [27.12,27.91,28.11,26.95] eng2 | 1 | [29.01,28.99,30.11,31.56] qa1 | 0 | [23.15,25.11,24.63,23.91] qa1 | 1 | [22.85,22.86,23.91,31.52] (6 rows)