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Flex map functions

The flex map functions let you extract and manipulate nested map data.

1: EMPTYMAP
2: MAPAGGREGATE
3: MAPCONTAINSKEY
4: MAPCONTAINSVALUE
5: MAPITEMS
6: MAPKEYS
7: MAPKEYSINFO
8: MAPLOOKUP
9: MAPPUT
10: MAPSIZE
11: MAPTOSTRING
12: MAPVALUES
13: MAPVERSION

The flex map functions let you extract and manipulate nested map data.

The first argument of all flex map functions (except EMPTYMAP and MAPAGGREGATE) takes a VMap. The VMap can originate from the __raw__ column in a flex table or be returned from a map or extraction function.

All map functions (except EMPTYMAP and MAPAGGREGATE) accept either a LONG VARBINARY or a LONG VARCHAR map argument.

In the following example, the outer MAPLOOKUP function operates on the VMap data returned from the inner MAPLOOKUP function:

=> MAPLOOKUP(MAPLOOKUP(ret_map, 'batch'), 'scripts')

You can use flex map functions exclusively with:

Flex tables
Their associated _keys tables and _view views
Flexible complex-type columns

1 - EMPTYMAP

Constructs a new VMap with one row but without keys or data.

Constructs a new VMap with one row but without keys or data. Use this transform function to populate a map without using a flex parser. Instead, you use either from SQL queries or from map data present elsewhere in the database.

Syntax

EMPTYMAP()

Examples

Create an Empty Map

=> SELECT EMPTYMAP();
                             emptymap
------------------------------------------------------------------
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
(1 row)

Create an Empty Map from an Existing Flex Table

If you create an empty map from an existing flex table, the new map has the same number of rows as the table from which it was created.

This example shows the result if you create an empty map from the darkdata table, which has 12 rows of JSON data:

=> SELECT EMPTYMAP() FROM darkdata;
                             emptymap
------------------------------------------------------------------
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
 \001\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000
(12 rows)

2 - MAPAGGREGATE

Returns a LONG VARBINARY VMap with key and value pairs supplied from two VARCHAR input columns.

Returns a LONG VARBINARY VMap with key and value pairs supplied from two VARCHAR input columns. This function requires an OVER clause.

Syntax

MAPAGGREGATE (keys-column1, values-column2 [USING PARAMETERS param=value[,...]])

Arguments

keys-column: Table column with the keys for the key/value pairs of the returned VMap data. Keys with a NULL value are excluded. If there are duplicate keys, the duplicate key and value that appear first in the query result are used, while the other duplicates are omitted.
values-column: Table column with the values for the key/value pairs of the returned VMap data.

Parameters

max_vmap_length

Maximum length in bytes for the VMap result, an integer between 1-32000000 inclusive.

Default: 130000

on_overflow

Overflow behavior for cases when the VMap result is larger than the max_vmap_length. The value must be one of the following strings:

'ERROR': Returns an error when overflow occurs.
'TRUNCATE': Stops aggregating key/value pairs if the result exceeds max_vmap_length. The query executes, but the resulting VMap does not have all key/value pairs. When the provided max_vmap_length is not large enough to store an empty VMap, the result returned is NULL. Note that you need to specify order criteria in the OVER clause to get consistent results.
'RETURN_NULL': Return NULL if overflow occurs.

Default: 'ERROR'

Examples

The following examples use this input table:

=> SELECT * FROM inventory;
  product     | stock
--------------+--------
  Planes      | 100
  Trains      | 50
  Automobiles | 200
(3 rows)

Call MAPAGGREGATE as follows to return the raw_map data of the resulting VMap:


=> SELECT raw_map FROM (SELECT MAPAGGREGATE(product, stock) OVER(ORDER BY product) FROM inventory) inventory;
raw_map
------------------------------------------------------------------------------------------------------------
\001\000\000\000\030\000\000\000\003\000\000\000\020\000\000\000\023\000\000\000\026\000\000\00020010050\003
\000\000\000\020\000\000\000\033\000\000\000!\000\000\000AutomobilesPlanesTrains
(1 row)

To transform the returned raw_map data into string representation, use MAPAGGREGATE with MAPTOSTRING:


=> SELECT MAPTOSTRING(raw_map) FROM (SELECT MAPAGGREGATE(product, stock) OVER(ORDER BY product) FROM
inventory) inventory;
MAPTOSTRING
--------------------------------------------------------------
{
  "Automobiles": "200",
  "Planes": "100",
  "Trains": "50"
}
(1 row)

If you run the above query with on_overflow left as default and a max_vmap_length less than the returned VMap size, the function returns with an error message indicating the need to increase VMap length:


=> SELECT MAPTOSTRING(raw_map) FROM (SELECT MAPAGGREGATE(product, stock USING PARAMETERS max_vmap_length=60)
OVER(ORDER BY product) FROM inventory) inventory;
----------------------------------------------------------------------------------------------------------
ERROR 5861:  Error calling processPartition() in User Function MapAggregate at [/data/jenkins/workspace
/RE-PrimaryBuilds/RE-Build-Master_2/server/udx/supported/flextable/Dict.cpp:1324], error code: 0, message:
Exception while finalizing map aggregation: Output VMap length is too small [60]. HINT: Set the parameter
max_vmap_length=71 and retry your query

Switching the value of on_overflow allows you to alter how MAPAGGREGATE behaves in the case of overflow. For example, changing on_overflow to 'RETURN_NULL' causes the above query to execute and return NULL:


SELECT raw_map IS NULL FROM (SELECT MAPAGGREGATE(product, stock USING PARAMETERS max_vmap_length=60,
on_overflow='RETURN_NULL') OVER(ORDER BY product) FROM inventory) inventory;
?column?
----------
t
(1 row)

If on_overflow is set to 'TRUNCATE', the resulting VMap has enough space for two of the key/value pairs, but must cut the third:


SELECT raw_map IS NULL FROM (SELECT MAPAGGREGATE(product, stock USING PARAMETERS max_vmap_length=60,
on_overflow='TRUNCATE') OVER(ORDER BY product) FROM inventory) inventory;
MAPTOSTRING
---------------------------------------------
{
  "Automobiles": "200",
  "Planes": "100"
}
(1 row)

3 - MAPCONTAINSKEY

Determines whether a VMap contains a virtual column (key).

Determines whether a VMap contains a virtual column (key). This scalar function returns true (t), if the virtual column exists, or false (f) if it does not. Determining that a key exists before calling maplookup() lets you distinguish between NULL returns. The maplookup() function uses for both a non-existent key and an existing key with a NULL value.

Syntax

MAPCONTAINSKEY (VMap-data, 'virtual-column-name')

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

virtual-column-name

Name of the key to check.

Examples

This example shows how to use the mapcontainskey() functions with maplookup(). View the results returned from both functions. Check whether the empty fields that maplookup() returns indicate a NULL value for the row (t) or no value (f):

You can use mapcontainskey( ) to determine that a key exists before calling maplookup(). The maplookup() function uses both NULL returns and existing keys with NULL values to indicate a non-existent key.

=> SELECT MAPLOOKUP(__raw__, 'user.location'), MAPCONTAINSKEY(__raw__, 'user.location')
FROM darkdata ORDER BY 1;
 maplookup | mapcontainskey
-----------+----------------
           | t
           | t
           | t
           | t
 Chile     | t
 Narnia    | t
 Uptown..  | t
 chicago   | t
           | f
           | f
           | f
           | f

(12 rows)

4 - MAPCONTAINSVALUE

Determines whether a VMap contains a specific value.

Determines whether a VMap contains a specific value. Use this scalar function to return true (t) if the value exists, or false (f) if it does not.

Syntax

MAPCONTAINSVALUE (VMap-data, 'virtual-column-value')

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

virtual-column-value

Value to confirm.

Examples

This example shows how to use mapcontainsvalue() to determine whether or not a virtual column contains a particular value. Create a flex table (ftest), and populate it with some virtual columns and values. Name both virtual columns one:

=> CREATE FLEX TABLE ftest();
CREATE TABLE
=> copy ftest from stdin parser fjsonparser();
Enter data to be copied followed by a newline.
End with a backslash and a period on a line by itself.
>> {"one":1, "two":2}
>> {"one":"one","2":"2"}
>> \.

Call mapcontainsvalue() on the ftest map data. The query returns false (f) for the first virtual column, and true (t) for the second , which contains the value one:


=> SELECT MAPCONTAINSVALUE(__raw__, 'one') FROM ftest;
mapcontainsvalue
------------------
f
t
(2 rows)

5 - MAPITEMS

Returns information about items in a VMap.

Returns information about items in a VMap. Use this transform function with one or more optional arguments to access polystructured values within the VMap data. This function requires an over()` clause.

Syntax

MAPITEMS (VMap-data [, passthrough-arg[,...] ])

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

max_key_length

In a __raw__ column, determines the maximum length of keys that the function can return. Keys that are longer than max_key_length cause the query to fail. Defaults to the smaller of VMap column length and 65K.

max_value_length

In a __raw__ column, determines the maximum length of values the function can return. Values that are larger than max_value_length cause the query to fail. Defaults to the smaller of VMap column length and 65K.

passthrough-arg

One or more arguments indicating keys within the map data in VMap-data.

Examples

The following examples illustrate using MAPITEMS()with the over(PARTITION BEST) clause.

This example determines the number of virtual columns in the map data using a flex table, labeled darkmountain. Query using the count() function to return the number of virtual columns in the map data:

=> SELECT COUNT(keys) FROM (SELECT MAPITEMS(darkmountain.__raw__) OVER(PARTITION BEST) FROM
 darkmountain) AS a;
 count
-------
    19
(1 row)

The next example determines what items exist in the map data:

=> SELECT * FROM (SELECT MAPITEMS(darkmountain.__raw__) OVER(PARTITION BEST) FROM darkmountain) AS a;
    keys     |    values
-------------+---------------
 hike_safety | 50.6
 name        | Mt Washington
 type        | mountain
 height      | 17000
 hike_safety | 12.2
 name        | Denali
 type        | mountain
 height      | 29029
 hike_safety | 34.1
 name        | Everest
 type        | mountain
 height      | 14000
 hike_safety | 22.8
 name        | Kilimanjaro
 type        | mountain
 height      | 29029
 hike_safety | 15.4
 name        | Mt St Helens
 type        | volcano
(19 rows)

The following example shows how to restrict the length of returned values to 100000:

=> SELECT LENGTH(keys), LENGTH(values) FROM (SELECT MAPITEMS(__raw__ USING PARAMETERS max_value_length=100000) OVER() FROM t1) x;
 LENGTH | LENGTH
--------+--------
      9 | 98899
(1 row)

Directly Query a Key Value in a VMap

Review the following JSON input file, simple.json. In particular, notice the array called three_Array, and its four values:

{
  "one": "one",
  "two": 2,
  "three_Array":
  [
    "three_One",
    "three_Two",
    3,
    "three_Four"
  ],
  "four": 4,
  "five_Map":
  {
    "five_One": 51,
    "five_Two": "Fifty-two",
    "five_Three": "fifty three",
    "five_Four": 54,
    "five_Five": "5 x 5"
  },
  "six": 6
}

Create a flex table, mapper:

=> CREATE FLEX TABLE mapper();
CREATE TABLE

Load simple.json into the flex table mapper:

=> COPY mapper FROM '/home/dbadmin/data/simple.json' parser fjsonparser (flatten_arrays=false,
flatten_maps=false);
 Rows Loaded
-------------
           1
(1 row)

Call MAPKEYS on the flex table's __raw__ column to see the flex table's keys, but not the key submaps. The return values indicate three_Array as one of the virtual columns:

=> SELECT MAPKEYS(__raw__) OVER() FROM mapper;
    keys
-------------
 five_Map
 four
 one
 six
 three_Array
 two
(6 rows)

Call mapitems on flex table mapper with three_Array as a pass-through argument to the function. The call returns these array values:

=> SELECT __identity__, MAPITEMS(three_Array) OVER(PARTITION BY __identity__) FROM mapper;
 __identity__ | keys |   values
--------------+------+------------
            1 | 0    | three_One
            1 | 1    | three_Two
            1 | 2    | 3
            1 | 3    | three_Four
(4 rows)

6 - MAPKEYS

Returns the virtual columns (and values) present in any VMap data.

Returns the virtual columns (and values) present in any VMap data. This transform function requires an OVER(PARTITION BEST) clause.

Syntax

MAPKEYS (VMap-data)

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

max_key_length

In a __raw__ column, specifies the maximum length of keys that the function can return. Keys that are longer than max_key_length cause the query to fail. Defaults to the smaller of VMap column length and 65K.

Examples

Determine Number of Virtual Columns in Map Data

This example shows how to create a query, using an over(PARTITION BEST) clause with a flex table, darkdata to find the number of virtual column in the map data. The table is populated with JSON tweet data.

=> SELECT COUNT(keys) FROM (SELECT MAPKEYS(darkdata.__raw__) OVER(PARTITION BEST) FROM darkdata) AS a;
 count
-------
   550
(1 row)

Query Ordered List of All Virtual Columns in the Map

This example shows a snippet of the return data when you query an ordered list of all virtual columns in the map data:

=> SELECT * FROM (SELECT MAPKEYS(darkdata.__raw__) OVER(PARTITION BEST) FROM darkdata) AS a;
    keys
-------------------------------------
 contributors
 coordinates
 created_ at
 delete.status.id
 delete.status.id_str
 delete.status.user_id
 delete.status.user_id_str
 entities.hashtags
 entities.media
 entities.urls
 entities.user_mentions
 favorited
 geo
 id
.
.
.
 user.statuses_count
 user.time_zone
 user.url
 user.utc_offset
 user.verified
(125 rows)

Specify the Maximum Length of Keys that MAPKEYS Can Return

=> SELECT MAPKEYS(__raw__ USING PARAMETERS max_key_length=100000) OVER() FROM mapper;
    keys
-------------
 five_Map
 four
 one
 six
 three_Array
 two
(6 rows)

7 - MAPKEYSINFO

Returns virtual column information from a given map.

Returns virtual column information from a given map. This transform function requires an OVER(PARTITION BEST) clause.

Syntax

MAPKEYSINFO (VMap-data)

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

max_key_length

Returns

This function is a superset of the MAPKEYS() function. It returns the following information about each virtual column:

Column	Description
`keys`	The virtual column names in the raw data.
`length`	The data length of the key name, which can differ from the actual string length.
`type_oid`	The OID type into which the value should be converted. Currently, the type is always `116` for a `LONG VARCHAR`, or `199` for a nested map that is stored as a `LONG VARBINARY`.
`row_num`	The number of rows in which the key was found.
`field_num`	The field number in which the key exists.

Examples

This example shows a snippet of the return data you receive if you query an ordered list of all virtual columns in the map data:

=> SELECT * FROM (SELECT MAPKEYSINFO(darkdata.__raw__) OVER(PARTITION BEST) FROM darkdata) AS a;
                          keys                           | length | type_oid | row_num | field_num
----------------------------------------------------------+--------+----------+---------+-----------
 contributors                                             |      0 |      116 |       1 |         0
 coordinates                                              |      0 |      116 |       1 |         1
 created_at                                               |     30 |      116 |       1 |         2
 entities.hashtags                                        |     93 |      199 |       1 |         3
 entities.media                                           |    772 |      199 |       1 |         4
 entities.urls                                            |     16 |      199 |       1 |         5
 entities.user_mentions                                   |     16 |      199 |       1 |         6
 favorited                                                |      1 |      116 |       1 |         7
 geo                                                      |      0 |      116 |       1 |         8
 id                                                       |     18 |      116 |       1 |         9
 id_str                                                   |     18 |      116 |       1 |        10
.
.
.
 delete.status.id                                         |     18 |      116 |      11 |         0
 delete.status.id_str                                     |     18 |      116 |      11 |         1
 delete.status.user_id                                    |      9 |      116 |      11 |         2
 delete.status.user_id_str                                |      9 |      116 |      11 |         3
 delete.status.id                                         |     18 |      116 |      12 |         0
 delete.status.id_str                                     |     18 |      116 |      12 |         1
 delete.status.user_id                                    |      9 |      116 |      12 |         2
 delete.status.user_id_str                                |      9 |      116 |      12 |         3
(550 rows)

Specify the Maximum Length of Keys that MAPKEYSINFO Can Return

=> SELECT MAPKEYSINFO(__raw__ USING PARAMETERS max_key_length=100000) OVER() FROM mapper;
    keys
-------------
 five_Map
 four
 one
 six
 three_Array
 two
(6 rows)

8 - MAPLOOKUP

Returns single-key values from VMAP data.

Returns single-key values from VMAP data. This scalar function returns a LONG VARCHAR, with values, or NULL if the virtual column does not have a value.

Using maplookup is case insensitive to virtual column names. To avoid loading same-name values, set the fjsonparser parser reject_on_duplicate parameter to true when data loading.

You can control the behavior for non-scalar values in a VMAP (like arrays), when loading data with the fjsonparser or favroparser parsers and its flatten-arrays argument. See JSON data and the FJSONPARSER reference.

For information about using maplookup() to access nested JSON data, see Querying nested data.

Syntax

MAPLOOKUP (VMap-data, 'virtual-column-name' [USING PARAMETERS [case_sensitive={false | true}] [, buffer_size=n] ] )

Parameters

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

virtual-column-name

The name of the virtual column whose values this function returns.

buffer_size

[Optional parameter] Specifies the maximum length (in bytes) of each value returned for virtual-column-name. To return all values for virtual-column-name, specify a buffer_size equal to or greater than (=>) the number of bytes for any returned value. Any returned values greater in length than buffer_size are rejected.

Default: 0 (No limit on buffer_size)

case_sensitive

[Optional parameter]

Specifies whether to return values for virtual-column-name if keys with different cases exist.

Example:

(... USING PARAMETERS case_sensitive=true)

Default: false

Examples

This example returns the values of one virtual column, user.location:

=> SELECT MAPLOOKUP(__raw__, 'user.location') FROM darkdata ORDER BY 1;
 maplookup
-----------
 Chile
 Nesnia
 Uptown
 .
 .
 chicago
(12 rows)

Using maplookup buffer_size

Use the buffer_size= parameter to indicate the maximum length of any value that maplookup returns for the virtual column you specify. If none of the returned key values can be greater than n bytes, use this parameter to allocate n bytes as the buffer_size.

For the next example, save this JSON data to a file, simple_name.json:

{
  "name": "sierra",
  "age": "63",
  "eyes": "brown",
  "weapon": "doggie"
}
{
  "name": "janis",
  "age": "10",
  "eyes": "blue",
  "weapon": "humor"
}
{
  "name": "ben",
  "age": "43",
  "eyes": "blue",
  "weapon": "sword"
}
{
  "name": "jen",
  "age": "38",
  "eyes": "green",
  "weapon": "shopping"
}

Create a flex table, logs.

Load the simple_name.json data into logs, using the fjsonparser. Specify the flatten_arrays option as True:

=> COPY logs FROM '/home/dbadmin/data/simple_name.json'
  PARSER fjsonparser(flatten_arrays=True);

Use maplookup with buffer_size=0 for the logs table name key. This query returns all of the values:

=> SELECT MAPLOOKUP(__raw__, 'name' USING PARAMETERS buffer_size=0) FROM logs;
 MapLookup
-----------
 sierra
 ben
 janis
 jen
(4 rows)

Next, call maplookup() three times, specifying the buffer_size parameter as 3, 5, and 6, respectively. Now, maplookup() returns values with a byte length less than or equal to (<=) buffer_size:

=> SELECT MAPLOOKUP(__raw__, 'name' USING PARAMETERS buffer_size=3) FROM logs;
 MapLookup
-----------

 ben

 jen
(4 rows)
=> SELECT MAPLOOKUP(__raw__, 'name' USING PARAMETERS buffer_size=5) FROM logs;
 MapLookup
-----------

 janis
 jen
 ben
(4 rows)
=> SELECT MAPLOOKUP(__raw__, 'name' USING PARAMETERS buffer_size=6) FROM logs;
 MapLookup
-----------
 sierra
 janis
 jen
 ben
(4 rows)

Disambiguate Empty Output Rows

This example shows how to interpret empty rows. Using maplookup without first checking whether a key exists can be ambiguous. When you review the following output, 12 empty rows, you cannot determine whether a user.location key has:

A non-NULL value
A NULL value
No value

=> SELECT MAPLOOKUP(__raw__, 'user.location') FROM darkdata;
 maplookup
-----------












(12 rows)

To disambiguate empty output rows, use the mapcontainskey() function in conjunction with maplookup(). When maplookup returns an empty field, the corresponding value from mapcontainskey indicates t for a NULL or other value, or ffor no value.

The following example output using both functions lists rows with NULL or a name value as t, and rows with no value as f:

=> SELECT MAPLOOKUP(__raw__, 'user.location'), MAPCONTAINSKEY(__raw__, 'user.location')
FROM darkdata ORDER BY 1;
 maplookup | mapcontainskey
-----------+----------------
           | t
           | t
           | t
           | t
 Chile     | t
 Nesnia    | t
 Uptown    | t
 chicago   | t
           | f >>>>>>>>>>No value
           | f >>>>>>>>>>No value
           | f >>>>>>>>>>No value
           | f >>>>>>>>>>No value
(12 rows)

Check for Case-Sensitive Virtual Columns

You can use maplookup() with the case_sensitive parameter to return results when key names with different cases exist.

Save the following sample content as a JSON file. This example saves the file as repeated_key_name.json:

{
  "test": "lower1"
}
{
  "TEST": "upper1"
}
{
  "TEst": "half1"
}
{
  "test": "lower2",
  "TEst": "half2"
}
{
  "TEST": "upper2",
  "TEst": "half3"
}
{
  "test": "lower3",
  "TEST": "upper3"
}
{
  "TEst": "half4",
  "test": "lower4",
  "TEST": "upper4"
}
{
  "TesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttest
TesttestTesttestTesttestTesttest":"1",
    "TesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttestTesttest
TesttestTesttestTesttestTesttestTest12345":"2"
}

Create a flex table, dupe, and load the JSON file:

=> CREATE FLEX TABLE dupe();
CREATE TABLE
dbt=> COPY dupe FROM '/home/release/KData/repeated_key_name.json' parser fjsonparser();
 Rows Loaded
-------------
           8
(1 row)

9 - MAPPUT

Accepts a VMap and one or more key/value pairs and returns a new VMap with the key/value pairs added.

Accepts a VMap and one or more key/value pairs and returns a new VMap with the key/value pairs added. Keys must be set using the auxiliary function SetMapKeys(), and can only be constant strings. If the VMap has any of the new input keys, then the original values are replaced by the new ones.

Syntax

MAPPUT (VMap-data, value[,...] USING PARAMETERS keys=SetMapKeys('key'[,...])

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP.
Other database content

value[,...]

One or more values to add to the VMap specified in VMap-data.

Parameters

keys: The result of SetMapKeys(). SetMapKeys() takes one or more constant string arguments.

The following example shows how to create a flex table and use COPY to enter some basic JSON data. After creating a second flex table, insert the new VMap results from mapput(), with additional key/value pairs.

Create sample table:

=> CREATE FLEX TABLE vmapdata1();
CREATE TABLE

Load sample JSON data from STDIN:

=> COPY vmapdata1 FROM stdin parser fjsonparser();
Enter data to be copied followed by a newline.
End with a backslash and a period on a line by itself.
>> {"aaa": 1, "bbb": 2, "ccc": 3}
>> \.

Create another flex table and use the function to insert data into it: => CREATE FLEX TABLE vmapdata2(); => INSERT INTO vmapdata2 SELECT MAPPUT(__raw__, '7','8','9' using parameters keys=SetMapKeys('xxx','yyy','zzz')) from vmapdata1;

View the difference between the original and the new flex tables:

=> SELECT MAPTOSTRING(__raw__) FROM vmapdata1;
                     maptostring
-----------------------------------------------------
 {
   "aaa" : "1",
   "bbb" : "2",
   "ccc" : "3"
 }
 (1 row)

=> SELECT MAPTOSTRING(__raw__) from vmapdata2;
                     maptostring
-------------------------------------------------------
 {
   "mapput" : {
      "aaa" : "1",
      "bbb" : "2",
      "ccc" : "3",
      "xxx" : "7",
      "yyy" : "8",
      "zzz" : "9"
   }
 }

10 - MAPSIZE

Returns the number of virtual columns present in any VMap data.

Returns the number of virtual columns present in any VMap data. Use this scalar function to determine the size of keys.

Syntax

MAPSIZE (VMap-data)

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

Examples

This example shows the returned sizes from the number of keys in the flex table darkmountain:

=> SELECT MAPSIZE(__raw__) FROM darkmountain;
 mapsize
---------
       3
       4
       4
       4
       4
(5 rows)

11 - MAPTOSTRING

Recursively builds a string representation of VMap data, including nested JSON maps.

Recursively builds a string representation of VMap data, including nested JSON maps. Use this transform function to display the VMap contents in a LONG VARCHAR format. You can use MAPTOSTRING to see how map data is nested before querying virtual columns with MAPVALUES.

Syntax

MAPTOSTRING ( VMap-data [ USING PARAMETERS param=value ] )

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

Parameters

canonical_json: Boolean, whether to produce canonical JSON format, using the first instance of any duplicate keys in the map data. If false, the function returns duplicate keys and their values.
Default: true

Examples

The following example uses this table definition and sample data:

=> CREATE FLEX TABLE darkdata();
CREATE TABLE

=> COPY darkdata FROM stdin parser fjsonparser();
Enter data to be copied followed by a newline.
End with a backslash and a period on a line by itself.
>> {"aaa": 1, "aaa": 2, "AAA": 3, "bbb": "aaa\"bbb"}
>> \.

Calling MAPTOSTRING with the default value of canonical_json returns only the first instance of the duplicate key:

=> SELECT MAPTOSTRING (__raw__) FROM darkdata;
                        maptostring
------------------------------------------------------------
 {
   "AAA" : "3",
   "aaa" : "1",
   "bbb" : "aaa\"bbb"
}
(1 row)

With canonical_json set to false, the function returns all of the keys, including duplicates:

=> SELECT MAPTOSTRING(__raw__ using parameters canonical_json=false) FROM darkdata;
                          maptostring
---------------------------------------------------------------
 {
        "aaa":  "1",
        "aaa":  "2",
        "AAA":  "3",
        "bbb":  "aaa"bbb"
 }
(1 row)

12 - MAPVALUES

Returns a string representation of the top-level values from a VMap.

Returns a string representation of the top-level values from a VMap. This transform function requires an OVER() clause.

Syntax

MAPVALUES (VMap-data)

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

max_value_length

In a __raw__ column, specifies the maximum length of values the function can return. Values that are larger than max_value_length cause the query to fail. Defaults to the smaller of VMap column length and 65K.

Examples

The following example shows how to query a darkmountain flex table, using an over() clause (in this case, the over(PARTITION BEST) clause) with mapvalues().

=> SELECT * FROM (SELECT MAPVALUES(darkmountain.__raw__) OVER(PARTITION BEST) FROM darkmountain) AS a;
    values
---------------
 29029
 34.1
 Everest
 mountain
 29029
 15.4
 Mt St Helens
 volcano
 17000
 12.2
 Denali
 mountain
 14000
 22.8
 Kilimanjaro
 mountain
 50.6
 Mt Washington
 mountain
(19 rows)

Specify the Maximum Length of Values that MAPVALUES Can Return

=> SELECT MAPVALUES(__raw__ USING PARAMETERS max_value_length=100000) OVER() FROM mapper;
    keys
-------------
 five_Map
 four
 one
 six
 three_Array
 two
(6 rows)

13 - MAPVERSION

Returns the version or invalidity of any map data.

Returns the version or invalidity of any map data. This scalar function returns the map version (such as 1) or -1, if the map data is invalid.

Syntax

MAPVERSION (VMap-data)

Arguments

VMap-data

Any VMap data. The VMap can exist as:

The __raw__ column of a flex table
Data returned from a map function such as MAPLOOKUP
Other database content

Examples

The following example shows how to use mapversion() with the darkmountainflex table, returning mapversion 1 for the flex table map data:

=> SELECT MAPVERSION(__raw__) FROM darkmountain;
 mapversion
------------
          1
          1
          1
          1
          1
(5 rows)

Flex map functions

1 - EMPTYMAP

Syntax

Examples

See also

2 - MAPAGGREGATE

Syntax

Arguments

Parameters

Examples

See also

3 - MAPCONTAINSKEY

Syntax

Arguments

Examples

See also

4 - MAPCONTAINSVALUE

Syntax

Arguments

Examples

See also

5 - MAPITEMS

Syntax

Arguments

Examples

See also

6 - MAPKEYS

Syntax

Arguments

Examples

See also

7 - MAPKEYSINFO

Syntax

Arguments

Returns

Examples

See also

8 - MAPLOOKUP

Syntax

Parameters

Examples

See also

9 - MAPPUT

Syntax

Arguments

Parameters

See also

10 - MAPSIZE

Syntax

Arguments

Examples

See also

11 - MAPTOSTRING

Syntax

Arguments

Parameters

Examples

See also

12 - MAPVALUES

Syntax

Arguments

Examples

See also

13 - MAPVERSION

Syntax

Arguments

Examples

See also