--- title: "list_value" slug: "dev-database-reference-sql-functions-lists-list-value" updated: 2026-10-30T18:19:06Z published: 2026-10-30T18:19:06Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-lists-list-value" --- > ## 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_value *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) › Build a list.* Returns a list of its arguments, in order. `list_pack` is the same function, and the bracket literal `[a, b, ...]` and `ARRAY[a, b, ...]` build the same list. ## Syntax ``` list_value(value, ...) list_pack(value, ...) [value, ...] ARRAY[value, ...] ``` | Argument | Type | Description | | --- | --- | --- | | `value` | any type; all of them must convert to one type | The elements of the list, in order. Zero or more. | **Returns:** a list (`T[]`) of the arguments' common type. **Aliases:** `list_pack`, `[...]`, `ARRAY[...]`. ## 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_value`. 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 four sensor readings, each with a low and a high value. The third has no high value and the last row 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_value"' 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}.readings" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, low BIGINT, high BIGINT, unit VARCHAR)") run(f"INSERT INTO {TABLE} VALUES " "(1, 10, 20, 'C'), " "(2, -5, 5, 'C'), " "(3, 7, NULL, 'F'), " "(4, NULL, NULL, NULL)") ``` ``` [] [] [(4,)] ``` ## What it does `list_value(a, b, ...)` returns the list `[a, b, ...]`. The four forms are interchangeable: `list_value(1, 2)`, `list_pack(1, 2)`, `[1, 2]` and `ARRAY[1, 2]` all return the `INTEGER[]` list `[1, 2]`. - **One element type.** The elements are converted to one common type. `[1, 2.5]` is a `DECIMAL(11,1)[]` list (the Python driver returns its elements as `Decimal` values); with a `DOUBLE`, `list_value(1, 2.5::DOUBLE)` is a `DOUBLE[]` list. `list_value(1, true)` returns `[1, 1]`. - **Lists of lists.** `[[1, 2], [3]]` is an `INTEGER[][]` list. The inner lists can have different lengths. - **NULL arguments become NULL elements.** `list_value(1, NULL)` is `[1, NULL]`; the list itself isn't NULL. - **A trailing comma is allowed** in the literal: `[1, 2,]` is `[1, 2]`. - **Lists compare element by element.** `[1, 2] = [1, 2]` is true and `[1, 2] = [2, 1]` is false. `<` and `>` compare the first elements that differ, and a list that runs out first is the smaller: `[1, 2] < [1, 3]`, `[1, 2] < [1, 2, 0]` and `[2] > [1, 9]` are all true. `[1, NULL] = [1, NULL]` is true. ## NULLs and edge cases | Input | Result | | --- | --- | | `list_value(NULL)` | `[NULL]` | | `list_value(1, NULL)` | `[1, NULL]` | | `list_value()`, `[]` | `[]`, of type `"NULL"[]` | | `[]::BIGINT[]` | `[]`, of type `BIGINT[]` | | `list_value(1, 2.5)` | `[1.0, 2.5]`, of type `DECIMAL(11,1)[]` | | `list_value(1, true)` | `[1, 1]` | | `[1, 2,]` | `[1, 2]` | | `[1, NULL] = [1, NULL]` | `true` | | `list_value(1, 'a')` | Error: `Could not convert string 'a' to INT32` | | `list_value([1], ['a'])` | Error: `Cannot create a list of types INTEGER[] and VARCHAR[] - an explicit cast is required` | The same cases, as the cluster returns them. They use the table and helpers from [Set up the examples](/develop/docs/dev-database-reference-sql-functions-lists-list-value#set-up-the-examples): ``` run("SELECT list_value(NULL), list_value(1, NULL), list_value(), [], []::BIGINT[]") run("SELECT typeof([]), typeof([]::BIGINT[]), list_value(1, 2.5), typeof(list_value(1, 2.5))") run("SELECT list_value(1, true), [1, 2,], [1, NULL] = [1, NULL], [1, 2] < [1, 2, 0], [2] > [1, 9]") run("SELECT list_value(1, 'a')") run("SELECT list_value([1], ['a'])") ``` ``` [([None], [1, None], [], [], [])] [('"NULL"[]', 'BIGINT[]', [Decimal('1.0'), Decimal('2.5')], 'DECIMAL(11,1)[]')] [([1, 1], [1, 2], True, True, True)] OSError: Could not convert string 'a' to INT32 InternalError: Binder Error: Cannot create a list of types INTEGER[] and VARCHAR[] - an explicit cast is required ``` ## Examples The low and high values of each reading as one list, in each of the four forms. A NULL column becomes a NULL element: ``` run(f"SELECT id, list_value(low, high), [low, high], list_pack(low, high), ARRAY[low, high] " f"FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, [10, 20], [10, 20], [10, 20], [10, 20]), (2, [-5, 5], [-5, 5], [-5, 5], [-5, 5]), (3, [7, None], [7, None], [7, None], [7, None]), (4, [None, None], [None, None], [None, None], [None, None])] ``` A list of a column and a constant: ``` run(f"SELECT id, [unit, 'K'] FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, ['C', 'K']), (2, ['C', 'K']), (3, ['F', 'K']), (4, [None, 'K'])] ``` Keep the readings whose low and high values are exactly 10 and 20: ``` run(f"SELECT id FROM {TABLE} WHERE [low, high] = [10, 20] ORDER BY id LIMIT 10") ``` ``` [(1,)] ``` ## 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`). VAST DataBase can evaluate a comparison of a column with a constant, but not a function of a column, so the list is always built by the Query Engine: - **In the `SELECT` list,** the scan reads the columns and the Query Engine builds the list for each row it returns. - **In `WHERE`,** the scan sends the columns for every row, and a `FILTER` step in the Query Engine builds the list and keeps the rows that match. The plan of the `WHERE` example shows the `FILTER` step above the scan: ``` plan(f"SELECT id FROM {TABLE} WHERE [low, high] = [10, 20]") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #2 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ (list_value(low, high) = │ │ [10, 20]) │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ low │ │ high │ │ id │ │ │ └───────────────────────────┘ ``` A list built this way is never NULL, so `list_value(low, high) IS NOT NULL` is always true: it returns every row, and its plan has no `FILTER` step: ``` plan(f"SELECT id FROM {TABLE} WHERE list_value(low, high) IS NOT NULL") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #2 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ low │ │ high │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **Compare the columns, not a list of them.** `low = 10 AND high = 20` is pushed down to VAST DataBase, so rows that don't match never leave storage; `[low, high] = [10, 20]` runs in a `FILTER` step. The plan of the column comparisons has no `FILTER` step: ``` plan(f"SELECT id FROM {TABLE} WHERE low = 10 AND high = 20") ``` ``` ┌───────────────────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ Projections: id │ │ │ └───────────────────────────┘ ``` - **Build lists in the `SELECT` list of the rows you keep.** Filter on plain columns first; the list is then built only for the rows that pass. ## Limitations and errors - **The elements must have a common type.** `list_value(1, 'a')` fails with `Could not convert string 'a' to INT32`, and lists of different element types fail with `Cannot create a list of types INTEGER[] and VARCHAR[] - an explicit cast is required`. Cast the values to one type first, for example `[CAST(1 AS VARCHAR), 'a']`. - **An empty list has no element type.** `[]` is of type `"NULL"[]`. Cast it when the type matters: `[]::BIGINT[]`. - **No list aggregate across rows.** `list(id)` and `array_agg(id)` fail with `The operator 'HASH_GROUP_BY' type=9 is currently not supported.` `list_value` builds a list from the values of one row only. ``` run("SELECT [CAST(1 AS VARCHAR), 'a'], typeof([]::VARCHAR[])") run(f"SELECT list(id) FROM {TABLE}") ``` ``` [(['1', 'a'], 'VARCHAR[]')] InternalError: The operator 'HASH_GROUP_BY' type=9 is currently not supported. ``` ## Similar functions | Function | Builds | Result | Type | | --- | --- | --- | --- | | `list_value(1, 2)`, `[1, 2]`, `list_pack(1, 2)` | a list of the arguments | `[1, 2]` | `INTEGER[]` | | [array_value](/develop/docs/dev-database-reference-sql-functions-lists-array-value) `(1, 2)` | a fixed-size array of the arguments | `[1, 2]` | `INTEGER[2]` | | [range](/develop/docs/dev-database-reference-sql-functions-lists-range) `(1, 3)` | the integers from 1 up to, not including, 3 | `[1, 2]` | `BIGINT[]` | | [generate_series](/develop/docs/dev-database-reference-sql-functions-lists-generate-series) `(1, 2)` | the integers from 1 up to and including 2 | `[1, 2]` | `BIGINT[]` | | [list_append](/develop/docs/dev-database-reference-sql-functions-lists-list-append), [list_concat](/develop/docs/dev-database-reference-sql-functions-lists-list-concat) | a list from an existing list | | | ``` run("SELECT list_value(1, 2), [1, 2], list_pack(1, 2), array_value(1, 2), range(1, 3), generate_series(1, 2)") run("SELECT typeof(list_value(1, 2)), typeof([1, 2]), typeof(array_value(1, 2))") ``` ``` [([1, 2], [1, 2], [1, 2], [1, 2], [1, 2], [1, 2])] [('INTEGER[]', 'INTEGER[]', 'INTEGER[2]')] ``` 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. - [Data types in SQL](/develop/docs/dev-database-reference-sql-data-types): list types. - [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.