--- title: "parse_filename" slug: "dev-database-reference-sql-functions-string-parse-filename" updated: 2026-10-30T18:18:56Z published: 2026-10-30T18:18:56Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-string-parse-filename" --- > ## 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. # parse_filename *Applies to VAST Cluster 5.5.* *[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Text basics](/develop/docs/dev-database-reference-sql-functions-string-text-basics) › Paths.* Returns the last component of a file path, the file name, optionally without its last extension. It has no aliases. ## Syntax ``` parse_filename(path) parse_filename(path, trim_extension) parse_filename(path, separator) parse_filename(path, trim_extension, separator) ``` | Argument | Type | Description | | --- | --- | --- | | `path` | `VARCHAR` | The path to read. | | `trim_extension` | `BOOLEAN` | Optional. `true` removes the last extension from the file name. The default is `false`, and `NULL` is treated as `false`. | | `separator` | `VARCHAR` | Optional. Which character separates components, as for [parse_path](/develop/docs/dev-database-reference-sql-functions-string-parse-path#what-it-does): `'forward_slash'`, `'backslash'`, `'both_slash'` or `'system'` (which means `/` on the cluster). Without it, with `NULL` or with any other value, `/` and `\` both separate components. | **Returns:** `VARCHAR`. **Aliases:** none. **Argument order.** `trim_extension` always comes before `separator`. With two arguments, the type of the second one decides what it is: a `BOOLEAN` is `trim_extension`, a `VARCHAR` is `separator`. A quoted `'true'` is a `VARCHAR`, so `parse_filename('a/b.txt', 'true')` reads it as an (unknown) separator and returns `'b.txt'` with the extension kept: write `true` without quotes. To pass both, write `parse_filename(path, true, 'backslash')`; the order `parse_filename(path, 'backslash', true)` fails with `No function matches the given name and argument types`. ## 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_parse_filename`. 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 file paths, with the file name stored next to each path. One path is a Windows path and one ends with a separator; 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_parse_filename"' 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, path VARCHAR, file_name VARCHAR)") run(f"INSERT INTO {TABLE} VALUES " "(1, '/data/logs/app.log', 'app.log'), " "(2, '/home/ada/projects/notes.tar.gz', 'notes.tar.gz'), " "(3, 'C:\\Users\\jose\\poems.docx', 'poems.docx'), " "(4, 'exports/2026/', ''), " "(5, NULL, NULL)") ``` ``` [] [] [(5,)] ``` ## What it does `parse_filename` returns what comes after the last separator of the path. A path that ends with a separator has nothing after it, and gives an empty string: | Path | Result | | --- | --- | | `'/data/logs/app.log'` | `'app.log'` | | `'C:\dir\file.tar.gz'` | `'file.tar.gz'` | | `'c'` | `'c'`: a path with no separator is a file name. | | `'a/b/'` | `''` | | `''` | `''` | **trim_extension.** With `true`, the file name loses its last extension: the last `.` of the file name and everything after it. Only one extension goes, a dot in a directory name doesn't count, and a name whose only `.` is its first character, such as `.bashrc`, is all extension: | Call | Result | | --- | --- | | `parse_filename('a/b/c.tar.gz', true)` | `'c.tar'` | | `parse_filename('a/b/c.tar.gz', false)` | `'c.tar.gz'` | | `parse_filename('c', true)` | `'c'`: no dot, nothing to remove. | | `parse_filename('c.', true)` | `'c'` | | `parse_filename('a.d/c', true)` | `'c'` | | `parse_filename('a/.b.txt', true)` | `'.b'` | | `parse_filename('.bashrc', true)` | `''` | **separator.** With `'forward_slash'`, only `/` separates components, so a backslash stays in the name; `'system'` means `/` on the cluster and does the same. With `'backslash'`, only `\` does. `'both_slash'`, `NULL` and a value that isn't a mode name split on both, as the default does: | Call | Result | | --- | --- | | `parse_filename('a\b.txt', 'forward_slash')` | `'a\b.txt'` | | `parse_filename('a\b.txt', 'system')` | `'a\b.txt'` | | `parse_filename('a\b.txt', 'both_slash')` | `'b.txt'` | | `parse_filename('a\b.txt', true, 'backslash')` | `'b'` | | `parse_filename('a\b.txt', true, NULL)` | `'b'` | | `parse_filename('a/b/c.txt', 'x')` | `'c.txt'`: a value that isn't a separator name is accepted without an error. | In Python code, write each `\` of a path as `\\` inside the string, so that the SQL receives one backslash. Python prints each backslash in the results doubled: `'a\\b.txt'` is the string `a\b.txt`. ## NULLs and edge cases | Input | Result | | --- | --- | | `NULL` | `NULL` | | `NULL` with `trim_extension` `true` | `NULL` | | `'a/b.txt'` with a `NULL` second argument | `'b.txt'` | | `''` (empty string) | `''` | | `'a/b/'` (trailing separator) | `''` | | `'c'` (no separator) | `'c'` | | `'c'` with `trim_extension` `true` (no dot) | `'c'` | | `'.bashrc'` with `trim_extension` `true` | `''` | | `'a/b/c.tar.gz'` with `trim_extension` `true` | `'c.tar'` | | `'a/b/c.tar.gz'` with `trim_extension` `false` | `'c.tar.gz'` | | `'a/b/c.txt'` with separator `'x'` | `'c.txt'` | | `'a\b.txt'` with separator `'forward_slash'` | `'a\b.txt'` | | `'a\b.txt'` with `trim_extension` `true` and separator `'backslash'` | `'b'` | | A number, decimal, date, boolean, `BLOB` or list as `path` | 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-parse-filename#set-up-the-examples): ``` run("SELECT parse_filename(NULL), parse_filename(NULL, true), parse_filename('a/b.txt', NULL), parse_filename('')") run("SELECT parse_filename('a/b/'), parse_filename('c'), parse_filename('c', true), parse_filename('.bashrc', true)") run("SELECT parse_filename('a/b/c.tar.gz', true), parse_filename('a/b/c.tar.gz', false), parse_filename('a/b/c.txt', 'x')") run("SELECT parse_filename('a\\b.txt', 'forward_slash'), parse_filename('a\\b.txt', true, 'backslash')") run("SELECT parse_filename(123)") ``` ``` [(None, None, 'b.txt', '')] [('', 'c', 'c', '')] [('c.tar', 'c.tar.gz', 'c.txt')] [('a\\b.txt', 'b')] InternalError: Binder Error: No function matches the given name and argument types 'parse_filename(INTEGER_LITERAL)'. You might need to add explicit type casts. ``` ## Examples The file name of each path, with and without its last extension. The path that ends with a separator has no file name: ``` run(f"SELECT id, parse_filename(path), parse_filename(path, true) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, 'app.log', 'app'), (2, 'notes.tar.gz', 'notes.tar'), (3, 'poems.docx', 'poems'), (4, '', ''), (5, None, None)] ``` The same paths read with `/` as the only separator, then with `\` as the only separator and the extension removed. With `'backslash'`, a path with no backslash is a single component, so the whole path comes back, less its extension: ``` run(f"SELECT id, parse_filename(path, 'forward_slash'), parse_filename(path, true, 'backslash') " f"FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, 'app.log', '/data/logs/app'), (2, 'notes.tar.gz', '/home/ada/projects/notes.tar'), (3, 'C:\\Users\\jose\\poems.docx', 'poems'), (4, '', 'exports/2026/'), (5, None, None)] ``` Find a file by name, wherever it is: ``` run(f"SELECT id, path FROM {TABLE} WHERE parse_filename(path) = 'app.log' ORDER BY id LIMIT 10") ``` ``` [(1, '/data/logs/app.log')] ``` ## 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 `parse_filename()` is always computed by the Query Engine: - **In the `SELECT` list,** the scan reads the column and the Query Engine computes `parse_filename()` for each row it returns. - **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `parse_filename()` 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 parse_filename(path) = 'app.log'") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ (parse_filename(path) = │ │ 'app.log') │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ path │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **Store the file name if you look files up by name.** Compute it when you write the rows and keep it in its own column. A comparison of a raw column with a constant is pushed down to VAST DataBase, so rows that don't match never leave storage. The plan for `file_name = 'app.log'` has no `FILTER` step: ``` plan(f"SELECT id FROM {TABLE} WHERE file_name = 'app.log'") ``` ``` ┌───────────────────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ Projections: id │ │ │ └───────────────────────────┘ ``` - **A suffix pattern on the raw path doesn't help.** `path LIKE '%/app.log'` isn't pushed down either: its plan has a `FILTER` step too. Store the file name instead. ``` plan(f"SELECT id FROM {TABLE} WHERE path LIKE '%/app.log'") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ suffix(path, '/app.log') │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ path │ │ id │ │ │ └───────────────────────────┘ ``` - **Combine it with a pushed-down condition.** In `id > 100 AND parse_filename(path) = 'app.log'`, `id > 100` is still evaluated in VAST DataBase, so `parse_filename()` runs only on the rows that pass it. ## Limitations and errors - **Strings only.** A number, a decimal, a date, a boolean, a `BLOB` or a list as `path` fails with `No function matches the given name and argument types`. - **`trim_extension` before `separator`.** The four forms are the ones in [Syntax](/develop/docs/dev-database-reference-sql-functions-string-parse-filename#syntax); there's no form that takes the separator first and `trim_extension` after it. - **Only the last extension.** `parse_filename('a/b/c.tar.gz', true)` returns `'c.tar'`, not `'c'`. - **A trailing separator gives `''`.** `parse_filename('a/b/')` returns `''`, while [parse_path](/develop/docs/dev-database-reference-sql-functions-string-parse-path) drops the trailing separator and ends its list with `'b'`. - **Unknown separator names aren't errors.** A value other than the mode names is accepted and splits on `/` and `\`. Check the spelling, and don't quote `true`: `'true'` is read as a separator name. ``` run("SELECT parse_filename('\\xAA'::BLOB)") run("SELECT parse_filename('a/b.txt', 'forward_slash', true)") ``` ``` InternalError: Binder Error: No function matches the given name and argument types 'parse_filename(BLOB)'. You might need to add explicit type casts. InternalError: Binder Error: No function matches the given name and argument types 'parse_filename(STRING_LITERAL, STRING_LITERAL, BOOLEAN)'. You might need to add explicit type casts. ``` ## Similar functions | Function | Returns | Result for `'/home/ada/notes.txt'` | Result for `'C:\dir\file.tar.gz'` | | --- | --- | --- | --- | | `parse_filename` | the last component | `'notes.txt'` | `'file.tar.gz'` | | `parse_filename` with `trim_extension` true | the last component without its last extension | `'notes'` | `'file.tar'` | | [parse_dirpath](/develop/docs/dev-database-reference-sql-functions-string-parse-dirpath) | the path without its last component | `'/home/ada'` | `'C:\dir'` | | [parse_dirname](/develop/docs/dev-database-reference-sql-functions-string-parse-dirname) | the top-level directory | `'/'` | `'C:'` | | [parse_path](/develop/docs/dev-database-reference-sql-functions-string-parse-path) | every component, as a list | `['/', 'home', 'ada', 'notes.txt']` | `['C:', 'dir', 'file.tar.gz']` | ``` run("SELECT parse_filename('/home/ada/notes.txt'), parse_filename('/home/ada/notes.txt', true), " "parse_dirpath('/home/ada/notes.txt'), parse_dirname('/home/ada/notes.txt'), parse_path('/home/ada/notes.txt')") run("SELECT parse_filename('C:\\dir\\file.tar.gz'), parse_filename('C:\\dir\\file.tar.gz', true), " "parse_dirpath('C:\\dir\\file.tar.gz'), parse_dirname('C:\\dir\\file.tar.gz'), parse_path('C:\\dir\\file.tar.gz')") ``` ``` [('notes.txt', 'notes', '/home/ada', '/', ['/', 'home', 'ada', 'notes.txt'])] [('file.tar.gz', 'file.tar', 'C:\\dir', 'C:', ['C:', 'dir', 'file.tar.gz'])] ``` 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. - [parse_path](/develop/docs/dev-database-reference-sql-functions-string-parse-path): the separator modes in detail. - [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.