--- title: "url_encode" slug: "dev-database-reference-sql-functions-string-url-encode" updated: 2026-10-30T18:18:56Z published: 2026-10-30T18:18:56Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-string-url-encode" --- > ## 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. # url_encode *Applies to VAST Cluster 5.5.* *[Functions](/develop/docs/dev-database-reference-sql-functions-index) β€Ί [Text basics](/develop/docs/dev-database-reference-sql-functions-string-text-basics) β€Ί Unicode and URLs.* Percent-encodes a string so it can be placed in a URL: spaces, reserved characters such as `&`, `=`, `/` and `?`, and characters outside ASCII become `%` followed by two hexadecimal digits for each UTF-8 byte. It has no aliases; [url_decode](/develop/docs/dev-database-reference-sql-functions-string-url-decode) reverses it. ## Syntax ``` url_encode(s) ``` | Argument | Type | Description | | --- | --- | --- | | `s` | `VARCHAR` | The string to encode. | **Returns:** `VARCHAR`. **Aliases:** none. ## 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_url_encode`. 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 file names. The last row has no name: ``` 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_url_encode"' 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}.files" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, name VARCHAR)") run(f"INSERT INTO {TABLE} VALUES " "(1, 'report-2026.pdf'), " "(2, 'Q3 results.xlsx'), " "(3, 'R&D plan.txt'), " "(4, 'caf\u00e9 menu.pdf'), " "(5, NULL)") ``` ``` [] [] [(5,)] ``` ## What it does `url_encode` turns the string into UTF-8 bytes and writes each byte either as itself or as `%` followed by its value in two upper-case hexadecimal digits: - **Kept as they are:** ASCII letters, digits and the four characters `-`, `.`, `_` and `~`. - **Encoded:** everything else, including the space, the characters that have a meaning in a URL (`/`, `?`, `#`, `&`, `=`, `+`, `%`) and every byte of a character outside ASCII. | Call | Result | | --- | --- | | `url_encode('Hello')` | `'Hello'` | | `url_encode('AZaz0189')` | `'AZaz0189'`: letters and digits are kept | | `url_encode('~-._')` | `'~-._'` | | `url_encode('a b')` | `'a%20b'`: a space is `%20`, not `+` | | `url_encode('a+b')` | `'a%2Bb'` | | `url_encode('?#%')` | `'%3F%23%25'` | | `url_encode('a b&c=d/é')` | `'a%20b%26c%3Dd%2F%C3%A9'`: `é` is the two bytes `C3 A9` | | `url_encode('e\u0301 🇫🇷 ẞ')` | `'e%CC%81%20%F0%9F%87%AB%F0%9F%87%B7%20%E1%BA%9E'`: the combining accent is `CC 81`, the flag 8 bytes, `ẞ` 3 bytes | Because `/` is encoded too, encode each part of a URL separately (a path segment, a query parameter's value) and join the parts with the separators, rather than encoding a whole URL. The encoding depends on the bytes, so the same-looking text in two Unicode forms gives two encodings: the decomposed `'e\u0301'` gives `e%CC%81`, the precomposed `é` gives `%C3%A9`. Apply [nfc_normalize](/develop/docs/dev-database-reference-sql-functions-string-nfc-normalize) first if you need one encoding for both. ## NULLs and edge cases | Input | Result | | --- | --- | | `NULL` | `NULL` | | `''` (empty string) | `''` | | `'~-._'` | `'~-._'` | | `'a+b'` | `'a%2Bb'` | | `'?#%'` | `'%3F%23%25'` | | `'AZaz0189'` | `'AZaz0189'` | | `'e\u0301'` and `'é'` | `'e%CC%81'` and `'%C3%A9'` | | A number, decimal, date, boolean, `BLOB` or list | Error: `No function matches the given name and argument types` | 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-string-url-encode#set-up-the-examples): ``` run("SELECT url_encode(NULL), url_encode(''), url_encode('~-._'), url_encode('a+b'), url_encode('?#%'), " "url_encode('AZaz0189')") run("SELECT url_encode('e\u0301'), url_encode('\u00e9'), url_encode('e\u0301 πŸ‡«πŸ‡· ẞ')") run("SELECT url_encode(123)") ``` ``` [(None, '', '~-._', 'a%2Bb', '%3F%23%25', 'AZaz0189')] [('e%CC%81', '%C3%A9', 'e%CC%81%20%F0%9F%87%AB%F0%9F%87%B7%20%E1%BA%9E')] InternalError: Binder Error: No function matches the given name and argument types 'url_encode(INTEGER_LITERAL)'. You might need to add explicit type casts. ``` ## Examples A download link for each file. The name is encoded as one path segment and joined to the fixed part of the URL with [||](/develop/docs/dev-database-reference-sql-functions-string-concat-operator); the NULL name gives a NULL link: ``` run(f"SELECT id, 'https://files.example.com/shared/' || url_encode(name) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, 'https://files.example.com/shared/report-2026.pdf'), (2, 'https://files.example.com/shared/Q3%20results.xlsx'), (3, 'https://files.example.com/shared/R%26D%20plan.txt'), (4, 'https://files.example.com/shared/caf%C3%A9%20menu.pdf'), (5, None)] ``` Find the names that change when they're encoded, that is, the ones that contain characters that aren't safe in a URL: ``` run(f"SELECT id, name FROM {TABLE} WHERE url_encode(name) <> name ORDER BY id LIMIT 10") ``` ``` [(2, 'Q3 results.xlsx'), (3, 'R&D plan.txt'), (4, 'cafΓ© menu.pdf')] ``` ## 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 `url_encode()` is always computed by the Query Engine: - **In the `SELECT` list,** the scan reads the column and the Query Engine computes `url_encode()` for each row it returns. - **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `url_encode()` 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 url_encode(name) <> name") ``` ``` β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”‚ PROJECTION β”‚ β”‚ ──────────────────── β”‚ β”‚ #1 β”‚ β”‚ β”‚ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”΄β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”‚ FILTER β”‚ β”‚ ──────────────────── β”‚ β”‚ (url_encode(name) != name)β”‚ β”‚ β”‚ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”΄β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”‚ VAST_SCAN β”‚ β”‚ ──────────────────── β”‚ β”‚ Function: VAST_SCAN β”‚ β”‚ β”‚ β”‚ Projections: β”‚ β”‚ name β”‚ β”‚ id β”‚ β”‚ β”‚ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ ``` ## Make it faster - **Filter on the raw column, encode in the `SELECT` list.** Encoding is for output: compare the stored name, not its encoding, in `WHERE`. A comparison of the raw column with a constant is pushed down to VAST DataBase, so rows that don't match never leave storage, and `url_encode()` runs only on the rows returned. The plan for `name = 'R&D plan.txt'` has no `FILTER` step: ``` plan(f"SELECT 'https://files.example.com/shared/' || url_encode(name) FROM {TABLE} WHERE name = 'R&D plan.txt'") ``` ``` β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”‚ PROJECTION β”‚ β”‚ ──────────────────── β”‚ β”‚ ('https://files.example β”‚ β”‚ .com/shared/' || β”‚ β”‚ url_encode(name)) β”‚ β”‚ β”‚ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”΄β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”‚ VAST_SCAN β”‚ β”‚ ──────────────────── β”‚ β”‚ Function: VAST_SCAN β”‚ β”‚ Projections: name β”‚ β”‚ β”‚ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ ``` - **Combine it with a pushed-down condition.** In `id > 100 AND url_encode(name) <> name`, `id > 100` is still evaluated in VAST DataBase, so `url_encode()` runs only on the rows that pass it. ## Limitations and errors - **Strings only.** A number, decimal, date, boolean, `BLOB` or list fails with `No function matches the given name and argument types`. Cast a number first: `url_encode(CAST(n AS VARCHAR))`. - **One encoding, no options.** Spaces are always `%20`, never `+`, and `/` is always encoded. There's no argument to keep characters unencoded. - **Unicode form matters.** See [What it does](/develop/docs/dev-database-reference-sql-functions-string-url-encode#what-it-does). ``` run("SELECT url_encode(123)") run("SELECT url_encode('\\xAA'::BLOB)") run("SELECT url_encode(CAST(123 AS VARCHAR))") ``` ``` InternalError: Binder Error: No function matches the given name and argument types 'url_encode(INTEGER_LITERAL)'. You might need to add explicit type casts. InternalError: Binder Error: No function matches the given name and argument types 'url_encode(BLOB)'. You might need to add explicit type casts. [('123',)] ``` ## Similar functions | Function | What it does | Result | | --- | --- | --- | | `url_encode` | percent-encodes a string | `url_encode('a b')` gives `'a%20b'` | | [url_decode](/develop/docs/dev-database-reference-sql-functions-string-url-decode) | reverses `url_encode` | `url_decode('a%20b')` gives `'a b'`; `url_decode(url_encode('a b/é'))` gives `'a b/é'` | | `to_base64` ([Binary, hash and UUID functions](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-to-base64)) | encodes a `BLOB` as Base64 text | `to_base64('a'::BLOB)` gives `'YQ=='` | ``` run("SELECT url_encode('a b'), url_decode('a%20b'), url_decode(url_encode('a b/\u00e9'))") run("SELECT to_base64('a'::BLOB)") ``` ``` [('a%20b', 'a b', 'a b/Γ©')] [('YQ==',)] ``` Clean up: ``` run(f"DROP TABLE IF EXISTS {TABLE}") run(f"DROP SCHEMA IF EXISTS {SCHEMA}") conn.close() ``` ``` [] [] ``` ## See also - [Text basics](/develop/docs/dev-database-reference-sql-functions-string-text-basics): all the text functions. - [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. - [url_decode](/develop/docs/dev-database-reference-sql-functions-string-url-decode) and [nfc_normalize](/develop/docs/dev-database-reference-sql-functions-string-nfc-normalize).