--- title: "map_contains_value" slug: "dev-database-reference-sql-functions-maps-map-contains-value" updated: 2026-10-30T18:18:46Z published: 2026-10-30T18:18:46Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-maps-map-contains-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. # map_contains_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) › Search a map.* Returns true if any key of a map has a given value, false if none has. ## Syntax ``` map_contains_value(map, value) ``` | Argument | Type | Description | | --- | --- | --- | | `map` | `MAP(K, V)` | The map to search. | | `value` | the map's value type `V`, or one that converts to it | The value to look for. | **Returns:** `BOOLEAN`. ## 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_maps_map_contains_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. A table can't return a `MAP` column, so the examples keep each map as two list columns, `codes` (the keys) and `counts` (the values), and build the map in the query with [map](/develop/docs/dev-database-reference-sql-functions-maps-map)`(codes, counts)`. This block connects, defines the `run()` and `plan()` helpers, and creates a table of five rows, each with a number `n` to look up. Row 2 has a NULL value, row 3 has empty lists (an empty map) 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_maps_map_contains_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}.langs" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, codes VARCHAR[], counts BIGINT[], code VARCHAR, n BIGINT)") run(f"INSERT INTO {TABLE} VALUES " "(1, ['en', 'de'], [1, 2], 'de', 10), " "(2, ['\u00e9', '\u00fc'], [NULL, 3], 'fr', -5), " "(3, [], [], '', 0), " "(4, NULL, NULL, NULL, NULL), " "(5, ['k1', 'k2', 'k3'], [10, 20, 30], 'k3', 2147483647)") ``` ``` [] [] [(5,)] ``` ## What it does `map_contains_value` is true if `value` equals the value of at least one key: - **Values only.** The keys aren't searched: `map_contains_value(MAP {'en': 'English', 'de': 'German'}, 'de')` is false. To search the keys, use [map_contains](/develop/docs/dev-database-reference-sql-functions-maps-map-contains); for a key with a given value, [map_contains_entry](/develop/docs/dev-database-reference-sql-functions-maps-map-contains-entry). - **Exact, typed comparison.** Strings must match exactly, so `'german'` doesn't find `'German'`. Numbers of different types compare by value: `1.0` finds the `INTEGER` value `1`. - **Any number of keys can share the value.** `map_contains_value(MAP {'a': 1, 'b': 1}, 1)` is true. - **Values that are lists** compare as whole lists: `map_contains_value(MAP {'a': [1, 2]}, [1, 2])` is true. ## NULLs and edge cases | Input | Result | | --- | --- | | A NULL map: `map_contains_value(NULL::MAP(VARCHAR, BIGINT), 1)` | `NULL` | | A NULL value: `map_contains_value(MAP {'a': 1}, NULL)` | `NULL` | | A NULL value in a map that has one: `map_contains_value(MAP {'a': NULL::BIGINT}, NULL)` | `NULL`: NULL never matches | | `map_contains_value(NULL, NULL)` | `NULL` | | `map_contains_value(MAP {}, 1)` (empty map) | `false` | | `map_contains_value(MAP {'en': 'English', 'de': 'German'}, 'german')` | `false` | | `map_contains_value(MAP {'en': 'English', 'de': 'German'}, 'de')` (a key) | `false` | | `map_contains_value(MAP {'a': 1, 'b': 1}, 1)` | `true` | | `map_contains_value(MAP {'a': 1}, 1.0)` | `true` | | `map_contains_value(MAP {'a': [1, 2]}, [1, 2])` | `true` | | `map_contains_value(MAP {'a': 1}, '1')` (a value of another type) | Error: `contains: Cannot match element of type 'VARCHAR' in a list of type 'INTEGER[]' - 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-maps-map-contains-value#set-up-the-examples): ``` run("SELECT map_contains_value(NULL::MAP(VARCHAR, BIGINT), 1), map_contains_value(MAP {'a': 1}, NULL), " "map_contains_value(MAP {'a': NULL::BIGINT}, NULL), map_contains_value(NULL, NULL), map_contains_value(MAP {}, 1)") run("SELECT map_contains_value(MAP {'en': 'English', 'de': 'German'}, 'german'), " "map_contains_value(MAP {'en': 'English', 'de': 'German'}, 'de'), map_contains_value(MAP {'a': 1, 'b': 1}, 1), " "map_contains_value(MAP {'a': 1}, 1.0), map_contains_value(MAP {'a': [1, 2]}, [1, 2])") run("SELECT map_contains_value(MAP {'a': 1}, '1')") ``` ``` [(None, None, None, None, False)] [(False, False, True, True, True)] InternalError: Binder Error: contains: Cannot match element of type 'VARCHAR' in a list of type 'INTEGER[]' - an explicit cast is required ``` ## Examples Whether each row's map has the value 2, and whether it has the row's own number `n` as a value. Only row 1 has the value 2; no row's map has its `n`; row 4's lists are NULL, so its map and the answers are NULL: ``` run(f"SELECT id, map_contains_value(map(codes, counts), 2), map_contains_value(map(codes, counts), n) " f"FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, True, False), (2, False, False), (3, False, False), (4, None, None), (5, False, False)] ``` Keep only the rows whose map has the value 2: ``` run(f"SELECT id FROM {TABLE} WHERE map_contains_value(map(codes, counts), 2) 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`). A map exists only inside the query: the scan sends the list columns, and the Query Engine builds the map and searches its values, row by row: - **In the `SELECT` list,** the Query Engine builds the map and computes `map_contains_value()` for each row it returns. - **In `WHERE`,** the scan sends the lists for every row, and a `FILTER` step in the Query Engine builds the map, searches it and keeps the rows that match. No rows are skipped in storage. The plan of the `WHERE` example shows the `FILTER` step above the scan: ``` plan(f"SELECT id FROM {TABLE} WHERE map_contains_value(map(codes, counts), 2)") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #2 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ contains(map_values("map" │ │ (codes, counts)), 2) │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ codes │ │ counts │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **Search the value list instead.** When the values are in a list column, [list_contains](/develop/docs/dev-database-reference-sql-functions-lists-list-contains)`(counts, 2)` asks the same question without building the map. It still runs in a `FILTER` step: ``` run(f"SELECT id FROM {TABLE} WHERE list_contains(counts, 2) ORDER BY id LIMIT 10") ``` ``` [(1,)] ``` - **Pair it with a pushed-down condition.** A comparison of a plain column with a constant, such as `id > 1`, is evaluated in VAST DataBase, so the rows it rules out never reach the `FILTER` step: ``` plan(f"SELECT id FROM {TABLE} WHERE id > 1 AND map_contains_value(map(codes, counts), 2)") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #0 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ contains(map_values("map" │ │ (codes, counts)), 2) │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ id │ │ codes │ │ counts │ │ │ └───────────────────────────┘ ``` - **Keep a value you filter on often in its own column.** A comparison such as `n = 10` is evaluated in VAST DataBase; a search of a map built in the query isn't. ## Limitations and errors - **The first argument must be a map.** A list, string, number, date or struct fails with `The provided argument is not a map`. - **The value must have the map's value type.** A string in a map with `INTEGER` values fails with `contains: Cannot match element of type 'VARCHAR' in a list of type 'INTEGER[]' - an explicit cast is required`; the error names the map's values as a list. Cast the value to the map's value type. - **NULL can't be found.** `map_contains_value(m, NULL)` is NULL for every map. To test for a key with a NULL value, use [map_contains_entry](/develop/docs/dev-database-reference-sql-functions-maps-map-contains-entry)`(m, key, NULL)`, or count the NULL values with [list_filter](/develop/docs/dev-database-reference-sql-functions-lists-list-filter): `len(list_filter(map_values(m), x -> x IS NULL)) > 0`. ``` run("SELECT map_contains_value([1], 1)") run("SELECT map_contains_value(MAP {'a': 1}, 'x')") run("SELECT map_contains_value(MAP {'a': NULL::BIGINT}, NULL), map_contains_entry(MAP {'a': NULL::BIGINT}, 'a', NULL), " "len(list_filter(map_values(MAP {'a': NULL::BIGINT}), x -> x IS NULL)) > 0") ``` ``` InternalError: Invalid Input Error: The provided argument is not a map InternalError: Binder Error: contains: Cannot match element of type 'VARCHAR' in a list of type 'INTEGER[]' - an explicit cast is required [(None, True, True)] ``` ## Similar functions | Function | Answers | Result for `MAP {'en': 'English', 'de': 'German'}` | | --- | --- | --- | | `map_contains_value(m, 'German')` | is `'German'` a value? | `true` | | [map_contains](/develop/docs/dev-database-reference-sql-functions-maps-map-contains)`(m, 'de')` | is `'de'` a key? | `true` | | [map_contains_entry](/develop/docs/dev-database-reference-sql-functions-maps-map-contains-entry)`(m, 'de', 'German')` | is `'de'` a key with the value `'German'`? | `true` | | [list_contains](/develop/docs/dev-database-reference-sql-functions-lists-list-contains)`(`[map_values](/develop/docs/dev-database-reference-sql-functions-maps-map-values)`(m), 'German')` | is `'German'` in the list of values? | `true` | ``` run("SELECT map_contains_value(MAP {'en': 'English', 'de': 'German'}, 'German'), " "map_contains(MAP {'en': 'English', 'de': 'German'}, 'de'), " "map_contains_entry(MAP {'en': 'English', 'de': 'German'}, 'de', 'German'), " "list_contains(map_values(MAP {'en': 'English', 'de': 'German'}), 'German')") ``` ``` [(True, True, True, True)] ``` 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 map functions. - [map_values](/develop/docs/dev-database-reference-sql-functions-maps-map-values): a map's values as a list. - [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.