--- title: "md5" slug: "dev-database-reference-sql-functions-binary-hash-uuid-md5" updated: 2026-10-30T18:18:51Z published: 2026-10-30T18:18:51Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-binary-hash-uuid-md5" --- > ## 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. # md5 *Applies to VAST Cluster 5.5.* *[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Binary, hash and UUID functions](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid) › Hashes.* Returns the MD5 digest of a string or of a `BLOB`, as a `VARCHAR` of 32 lower-case hexadecimal digits. For the same digest as a number, see [md5_number](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-md5-number). ## Syntax ``` md5(x) ``` | Argument | Type | Description | | --- | --- | --- | | `x` | `VARCHAR` or `BLOB` | The value to hash. | **Returns:** `VARCHAR` (32 characters). ## 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_binary_hash_uuid_md5`. 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 documents, each with a name and its first bytes. 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_binary_hash_uuid_md5"' 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}.documents" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, name VARCHAR, data BLOB)") run(f"INSERT INTO {TABLE} VALUES " "(1, 'hello', '\\x25\\x50\\x44\\x46'::BLOB), " "(2, '', ''::BLOB), " "(3, 'a', '\\x61'::BLOB), " "(4, NULL, NULL)") ``` ``` [] [] [(4,)] ``` ## What it does `md5` computes the 128-bit MD5 digest of its argument and writes it as 32 hexadecimal digits, in lower case: `md5('abc')` is `'900150983cd24fb0d6963f7d28e17f72'`. A `VARCHAR` is hashed as its UTF-8 bytes, so a string and the same bytes as a `BLOB` have the same digest: `md5('hello')`, `md5('hello'::BLOB)` and `md5(encode('hello'))` are equal. The digest depends on every byte: `md5('Hello')` and `md5('hello')` differ. Use it for checksums, change detection and keys built from content. MD5 isn't suitable for passwords or signatures. ## NULLs and edge cases | Input | Result | | --- | --- | | `NULL` | `NULL` | | `''` (empty string) or `''::BLOB` | `'d41d8cd98f00b204e9800998ecf8427e'`, the digest of no bytes | | `md5('hello') = md5('hello'::BLOB)` | `true` | | `md5('hello') = md5(encode('hello'))` | `true` | | `upper(md5('abc')) = md5('abc')` | `false`: the digest is lower case | | `length(md5('a'))` | `32` | | A number: `md5(123)` | Error: `No function matches the given name and argument types`; cast it to `VARCHAR` | | A date, boolean, `UUID`, `BIT` or list | Error: `No function matches the given name and argument types` | | Two arguments: `md5('a', 'b')` | Error: `No function matches the given name and argument types` | The same cases, as the cluster returns them. They use the helpers from [Set up the examples](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-md5#set-up-the-examples): ``` run("SELECT md5(NULL), md5(''), md5(''::BLOB), length(md5('a'))") run("SELECT md5('hello') = md5('hello'::BLOB), md5('hello') = md5(encode('hello')), upper(md5('abc')) = md5('abc')") run("SELECT md5(123)") run("SELECT md5(CAST(42 AS VARCHAR))") run("SELECT md5('a', 'b')") ``` ``` [(None, 'd41d8cd98f00b204e9800998ecf8427e', 'd41d8cd98f00b204e9800998ecf8427e', 32)] [(True, True, False)] InternalError: Binder Error: No function matches the given name and argument types 'md5(INTEGER_LITERAL)'. You might need to add explicit type casts. [('a1d0c6e83f027327d8461063f4ac58a6',)] InternalError: Binder Error: No function matches the given name and argument types 'md5(STRING_LITERAL, STRING_LITERAL)'. You might need to add explicit type casts. ``` ## Examples The digest of each document's name and of its bytes: ``` run(f"SELECT id, md5(name), md5(data) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, '5d41402abc4b2a76b9719d911017c592', 'bfa4b10a76324b166cfdad5e02a63730'), (2, 'd41d8cd98f00b204e9800998ecf8427e', 'd41d8cd98f00b204e9800998ecf8427e'), (3, '0cc175b9c0f1b6a831c399e269772661', '0cc175b9c0f1b6a831c399e269772661'), (4, None, None)] ``` Find a document by the digest of its name: ``` run(f"SELECT id, name FROM {TABLE} WHERE md5(name) = '5d41402abc4b2a76b9719d911017c592' ORDER BY id LIMIT 10") ``` ``` [(1, 'hello')] ``` ## 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`). `md5()` is computed by the Query Engine: - **On a column in the `SELECT` list,** the scan reads the column and the Query Engine computes the digest for each row it returns. - **On a column in `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine hashes each value and keeps the rows that match. No rows are skipped in storage. - **On a constant,** such as `name = md5('x')`, the Query Engine computes the digest once, before the scan, and the comparison of the column with it is pushed down to VAST DataBase. The plan of the `WHERE` example shows the `FILTER` step above the scan: ``` plan(f"SELECT id FROM {TABLE} WHERE md5(name) = '5d41402abc4b2a76b9719d911017c592'") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ (md5(name) = │ │'5d41402abc4b2a76b9719d9110│ │ 17c592') │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ name │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **Store the digest if you look rows up by it.** Compute `md5()` when you write the rows and keep it in its own `VARCHAR` column. A lookup is then a comparison of a column with a constant, which VAST DataBase evaluates: the plan for a comparison with `md5('x')` has no `FILTER` step, because the digest of the constant is computed once: ``` plan(f"SELECT id FROM {TABLE} WHERE name = md5('x')") ``` ``` ┌───────────────────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ Projections: id │ │ │ └───────────────────────────┘ ``` ## Limitations and errors - **Strings and bytes only.** A number, a `DECIMAL`, a date, a boolean, a `UUID` or a `BIT` value fails with `No function matches the given name and argument types`, and the error lists `md5(VARCHAR)` and `md5(BLOB)`. Cast the value to `VARCHAR` first: `md5(CAST(42 AS VARCHAR))`, `md5(CAST(u AS VARCHAR))` for a `UUID` column. - **Lower case only.** Compare the result with a lower-case digest, or apply `lower()` to the other side; [hex](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-hex) writes capitals. - **Other names aren't available.** `md5_hex` and `sha512` fail with `Scalar Function with name ... does not exist!`. Use `md5`, or [sha1](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-sha1) and [sha256](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-sha256). ``` run("SELECT md5(DATE '2026-10-16')") run("SELECT md5_hex('a')") run("SELECT sha512('a')") ``` ``` InternalError: Binder Error: No function matches the given name and argument types 'md5(DATE)'. You might need to add explicit type casts. InternalError: Catalog Error: Scalar Function with name md5_hex does not exist! InternalError: Catalog Error: Scalar Function with name sha512 does not exist! ``` ## Similar functions | Function | Result | Type | For `'hello'` | | --- | --- | --- | --- | | `md5` | 128-bit digest as 32 hex digits | `VARCHAR` | `'5d41402abc4b2a76b9719d911017c592'` | | [md5_number](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-md5-number) | the same digest as a signed 128-bit number | `HUGEINT` | `-145191729247072235933599665601768308387` | | [md5_number_upper](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-md5-number-upper), [md5_number_lower](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-md5-number-lower) | 8 of the digest's 16 bytes as a number | `UBIGINT` | `8514701317032132957`, `10575884659879408057` | | [sha1](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-sha1) | 160-bit digest as 40 hex digits | `VARCHAR` | `'aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d'` | | [sha256](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-sha256) | 256-bit digest as 64 hex digits | `VARCHAR` | `'2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824'` | | [hash](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-hash) | a 64-bit hash, not a standard digest | `UBIGINT` | (not a standard value: compare hashes only with each other) | ``` run("SELECT md5('hello'), md5_number('hello'), md5_number_upper('hello'), md5_number_lower('hello')") run("SELECT sha1('hello'), sha256('hello'), typeof(hash('hello'))") ``` ``` [('5d41402abc4b2a76b9719d911017c592', Decimal('-145191729247072235933599665601768308387'), 8514701317032132957, 10575884659879408057)] [('aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d', '2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824', 'UBIGINT')] ``` Clean up: ``` run(f"DROP TABLE IF EXISTS {TABLE}") run(f"DROP SCHEMA IF EXISTS {SCHEMA}") conn.close() ``` ``` [] [] ``` ## See also - [Binary, hash and UUID functions](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid): all the functions in this family. - [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.