--- title: "list_reverse_sort" slug: "dev-database-reference-sql-functions-lists-list-reverse-sort" updated: 2026-10-30T18:19:06Z published: 2026-10-30T18:19:06Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-lists-list-reverse-sort" --- > ## Documentation Index > Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt > Use this file to discover all available pages before exploring further. # list_reverse_sort *Applies to VAST Cluster 5.5.* *[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [List, struct and map functions](/develop/docs/dev-database-reference-sql-functions-lists-and-structs) › Sort a list.* Returns the elements of a list sorted from largest to smallest. An optional argument chooses whether NULL elements go last (the default) or first. `array_reverse_sort` is the same function. ## Syntax ``` list_reverse_sort(l) list_reverse_sort(l, nulls) array_reverse_sort(l) array_reverse_sort(l, nulls) ``` | Argument | Type | Description | | --- | --- | --- | | `l` | a list of any type whose values can be compared | The list to sort. | | `nulls` | `VARCHAR` | `'NULLS LAST'` (the default) or `'NULLS FIRST'`. | **Returns:** a list of the same type as `l`. **Aliases:** `array_reverse_sort`. ## Set up the examples The examples connect with the ADBC driver, as in [VAST Query Engine (ADBC)](/develop/docs/dev-database-integrations-adbc), and work in a schema called `docs_sql_fn_lists_list_reverse_sort`. Set `QE_ENDPOINT`, `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY` and `VASTDB_BUCKET` ([SQL reference](/develop/docs/dev-database-reference-sql-index#example-connect-and-use-a-transaction)), and run the blocks in order in one Python session. Below each block is the output you should see. This block connects, defines the `run()` and `plan()` helpers, and creates a table of five rows of lists: numbers, words and measurements. Row 3 has empty lists and row 4 has no values: ``` import os import re import adbc_driver_manager import adbc_driver_manager.dbapi as dbapi import adbc_driver_vastdb BUCKET = os.environ["VASTDB_BUCKET"] SCHEMA = f'"{BUCKET}/docs_sql_fn_lists_list_reverse_sort"' conn = dbapi.connect( driver=adbc_driver_vastdb.get_driver_path(), db_kwargs={ "vast.db.endpoint": os.environ["QE_ENDPOINT"], "vast.db.access_key": os.environ["AWS_ACCESS_KEY_ID"], "vast.db.secret_key": os.environ["AWS_SECRET_ACCESS_KEY"], }, autocommit=True, ) def server_message(e): """The server's message in a driver error, without the request ID or the echoed statement.""" text = re.sub(r"\[req=0x[0-9a-f]+\]: ", "", str(e)) found = (re.search(r'message: "(.*?)", request_id', text, re.S) or re.search(r"description: (.*)\)", text, re.S)) message = found.group(1) if found else text.strip().splitlines()[-1] message = re.sub(r"^Plan query: '.*?' failed with: ", "", message, flags=re.S) message = re.split(r"\\n|\n", message)[0].replace('\\"', '"') return message.replace(BUCKET, "") def run(sql): """Run one statement. Print the rows it returns, or the error.""" try: with conn.cursor() as cur: cur.execute(sql) rows = cur.fetchall() if cur.description else [] except (adbc_driver_manager.Error, OSError) as e: print(f"{type(e).__name__}: {server_message(e)}") else: print(rows) def plan(sql): """Print the plan without its ~N Rows lines: the table's row count, which can still be 0 just after an insert.""" with conn.cursor() as cur: cur.execute("EXPLAIN " + sql) steps = cur.fetchall()[0][1] print("\n".join(line for line in steps.splitlines() if "Rows" not in line)) TABLE = f"{SCHEMA}.samples" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, nums BIGINT[], words VARCHAR[], vals DOUBLE[])") run(f"INSERT INTO {TABLE} VALUES " "(1, [1, 2, 3], ['a', 'b', 'c'], [0.5, 2.5, -1.0]), " "(2, [3, NULL, 3], ['b', NULL, 'B'], [2.0, NULL]), " "(3, [], [], []), " "(4, NULL, NULL, NULL), " "(5, [-5, 0, -5, 10], ['\u00e9', 'Zo\u00eb', '\U0001F1EB\U0001F1F7', ''], [1e308, 1e308, -1e-308])") ``` ``` [] [] [(5,)] ``` ## What it does `list_reverse_sort(l)` returns the elements of `l` from largest to smallest, and keeps duplicates: `[-5, 0, -5, 10]` sorts to `[10, 0, -5, -5]`. It gives the same result as [list_sort](/develop/docs/dev-database-reference-sql-functions-lists-list-sort)`(l, 'DESC')`. - **NULL elements go last** by default: `[2, NULL, 1]` sorts to `[2, 1, NULL]`. Pass `'NULLS FIRST'` to put them first. - **Values compare as in `list_sort`, in reverse.** `NaN` comes before `inf`; text sorts by character code, so lower case comes before capitals (`['b', 'A', 'a', 'B']` sorts to `['b', 'a', 'B', 'A']`); `true` comes before `false`; the latest date comes first; and lists compare element by element (`[[2], [1, 9], [1], []]`). - **The second argument is only for NULLs.** It takes no direction: `'DESC'` or `'ASC'` there is an error. For ascending order, use `list_sort`. ## NULLs and edge cases | Input | Result | | --- | --- | | `list_reverse_sort(NULL)` | `NULL` | | `list_reverse_sort([])` | `[]` | | `list_reverse_sort([NULL, NULL])` | `[NULL, NULL]` | | `list_reverse_sort([2, NULL, 1])` | `[2, 1, NULL]` | | `list_reverse_sort([2, NULL, 1], 'NULLS FIRST')` | `[NULL, 2, 1]` | | `list_reverse_sort([2, NULL, 1], 'NULLS LAST')` | `[2, 1, NULL]` | | `list_reverse_sort([2, 1], NULL)` | `NULL` | | `list_reverse_sort(['NaN'::DOUBLE, 1.0, -'inf'::DOUBLE, 'inf'::DOUBLE, NULL])` | `[nan, inf, 1.0, -inf, NULL]` | | `list_reverse_sort([2, NULL, 1], 'DESC')` | Error: `Not implemented Error: Enum value: unrecognized value "DESC" for enum "OrderByNullType"` | | `list_reverse_sort([2, NULL, 1], 'NULLS FIRST', 'ASC')` | Error: `No function matches the given name and argument types 'list_reverse_sort(INTEGER[], STRING_LITERAL, STRING_LITERAL)'` | | A string or a number instead of a list | Error: `No function matches the given name and argument types`, for example `'list_reverse_sort(INTEGER_LITERAL)'` | The same cases, as the cluster returns them. They use the helpers from [Set up the examples](/develop/docs/dev-database-reference-sql-functions-lists-list-reverse-sort#set-up-the-examples): ``` run("SELECT list_reverse_sort(NULL), list_reverse_sort([]), list_reverse_sort([NULL, NULL]), list_reverse_sort([2, NULL, 1])") run("SELECT list_reverse_sort([2, NULL, 1], 'NULLS FIRST'), list_reverse_sort([2, NULL, 1], 'NULLS LAST'), " "list_reverse_sort([2, 1], NULL)") run("SELECT list_reverse_sort(['NaN'::DOUBLE, 1.0, -'inf'::DOUBLE, 'inf'::DOUBLE, NULL]), " "list_reverse_sort(['b', 'A', 'a', 'B']), list_reverse_sort([[2], [1, 9], [1], []])") run("SELECT list_reverse_sort([2, NULL, 1], 'DESC')") run("SELECT list_reverse_sort([2, NULL, 1], 'NULLS FIRST', 'ASC')") run("SELECT list_reverse_sort(123)") ``` ``` [(None, [], [None, None], [2, 1, None])] [([None, 2, 1], [2, 1, None], None)] [([nan, inf, 1.0, -inf, None], ['b', 'a', 'B', 'A'], [[2], [1, 9], [1], []])] InternalError: Not implemented Error: Enum value: unrecognized value "DESC" for enum "OrderByNullType" InternalError: Binder Error: No function matches the given name and argument types 'list_reverse_sort(INTEGER[], STRING_LITERAL, STRING_LITERAL)'. You might need to add explicit type casts. InternalError: Binder Error: No function matches the given name and argument types 'list_reverse_sort(INTEGER_LITERAL)'. You might need to add explicit type casts. ``` ## Examples Each row's numbers from largest to smallest, the same with NULLs first, and the words in reverse order with `array_reverse_sort`: ``` run(f"SELECT id, list_reverse_sort(nums), list_reverse_sort(nums, 'NULLS FIRST'), array_reverse_sort(words) " f"FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, [3, 2, 1], [3, 2, 1], ['c', 'b', 'a']), (2, [3, 3, None], [None, 3, 3], ['b', 'B', None]), (3, [], [], []), (4, None, None, None), (5, [10, 0, -5, -5], [10, 0, -5, -5], ['🇫🇷', 'é', 'Zoë', ''])] ``` The largest two measurements of each row: sort in reverse, then take the first two elements with a slice: ``` run(f"SELECT id, list_reverse_sort(vals)[1:2] FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, [2.5, 0.5]), (2, [2.0, None]), (3, []), (4, None), (5, [1e+308, 1e+308])] ``` ## How it runs in VAST The Query Engine runs on the cluster's CNodes, and a query on a table starts with a scan in VAST DataBase (`VAST_SCAN`). The scan reads a list column whole, and `list_reverse_sort()` always runs in the Query Engine: - **In the `SELECT` list,** a projection step sorts each row's list after the scan. - **In `WHERE`,** the scan sends the list for every row, and a `FILTER` step sorts it and keeps the rows that match. No rows are skipped in storage. A condition on the largest element shows the `FILTER` step above the scan: ``` plan(f"SELECT id FROM {TABLE} WHERE list_reverse_sort(nums)[1] > 5") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ (array_extract │ │ (list_reverse_sort(nums), │ │ 1) > 5) │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ nums │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **Add a condition on a plain column.** A comparison of a column with a constant, such as `id > 1`, is evaluated in VAST DataBase, so `list_reverse_sort()` runs only on the rows that pass it. The plan for `id > 1` alone has no `FILTER` step: ``` plan(f"SELECT id FROM {TABLE} WHERE id > 1") ``` ``` ┌───────────────────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ Projections: id │ │ │ └───────────────────────────┘ ``` - **Use `list_max` for the largest element.** [list_max](/develop/docs/dev-database-reference-sql-functions-lists-list-max)`(l)` returns it directly. - **Store values you filter on in their own column.** A condition on a list always runs in the Query Engine; a comparison of a plain column with a constant is pushed down. ## Limitations and errors - **No direction argument.** `'DESC'` or `'ASC'` as the second argument fails with `Enum value: unrecognized value ... for enum "OrderByNullType"`, and a third argument fails with `No function matches the given name and argument types`. - **Lists only.** Another type fails with `No function matches the given name and argument types`; the error lists the accepted forms, `list_reverse_sort(ANY[])` and `list_reverse_sort(ANY[], VARCHAR)`. ## Similar functions | Function | Result for `[3, 1, NULL, 3, 10]` | | --- | --- | | `list_reverse_sort` | `[10, 3, 3, 1, NULL]` | | `list_reverse_sort(l, 'NULLS FIRST')` | `[NULL, 10, 3, 3, 1]` | | [list_sort](/develop/docs/dev-database-reference-sql-functions-lists-list-sort)`(l, 'DESC')` | `[10, 3, 3, 1, NULL]` | | [list_reverse](/develop/docs/dev-database-reference-sql-functions-lists-list-reverse) | `[10, 3, NULL, 1, 3]`: back to front, not sorted | | [list_max](/develop/docs/dev-database-reference-sql-functions-lists-list-max) | `10`: the largest element only | ``` run("SELECT list_reverse_sort(l), list_reverse_sort(l, 'NULLS FIRST'), list_sort(l, 'DESC'), list_reverse(l), list_max(l) " "FROM (SELECT [3, 1, NULL, 3, 10] AS l)") ``` ``` [([10, 3, 3, 1, None], [None, 10, 3, 3, 1], [10, 3, 3, 1, None], [10, 3, None, 1, 3], 10)] ``` Clean up: ``` run(f"DROP TABLE IF EXISTS {TABLE}") run(f"DROP SCHEMA IF EXISTS {SCHEMA}") conn.close() ``` ``` [] [] ``` ## See also - [List, struct and map functions](/develop/docs/dev-database-reference-sql-functions-lists-and-structs): all the list functions. - [list_sort](/develop/docs/dev-database-reference-sql-functions-lists-list-sort): ascending and descending order. - [Where filters run](/develop/docs/dev-database-reference-sql-select#where-filters-run) and [pushdowns](/develop/docs/dev-database-reference-pushdowns). - [EXPLAIN](/develop/docs/dev-database-reference-sql-explain): how to read a plan.