--- title: "regexp_extract_all" slug: "dev-database-reference-sql-functions-string-regexp-extract-all" updated: 2026-10-30T18:18:56Z published: 2026-10-30T18:18:56Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-string-regexp-extract-all" --- > ## 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. # regexp_extract_all *Applies to VAST Cluster 5.5.* *[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Regular expressions](/develop/docs/dev-database-reference-sql-functions-string-regular-expressions) › Regular expressions.* `regexp_extract_all(s, pattern)` returns a list of every part of `s` that the regular expression `pattern` matches, from left to right. With a group number it returns that group of each match. ## Syntax ``` regexp_extract_all(s, pattern) regexp_extract_all(s, pattern, group) regexp_extract_all(s, pattern, group, options) ``` | Argument | Type | Description | | --- | --- | --- | | `s` | `VARCHAR` | The string to search. | | `pattern` | `VARCHAR` | The regular expression ([syntax](/develop/docs/dev-database-reference-sql-functions-string-regexp-syntax)). A constant or a column. | | `group` | `INTEGER` | Optional. `0` (the default) returns each whole match; `1` or more the group with that number. It can come from a column. | | `options` | `VARCHAR` | Optional, a constant. Flags such as `'i'` (ignore case); see [options](/develop/docs/dev-database-reference-sql-functions-string-regexp-syntax#what-it-does). | **Returns:** `VARCHAR[]`. ## 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_string_regexp_extract_all`. 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 request logs. Log 3 is empty, 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_string_regexp_extract_all"' 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}.requests" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, query VARCHAR)") run(f"INSERT INTO {TABLE} VALUES " "(1, 'user=ada&id=17&id=42'), " "(2, 'Tag=SQL&tag=vast'), " "(3, ''), " "(4, NULL)") ``` ``` [] [] [(4,)] ``` ## What it does `regexp_extract_all` scans `s` from left to right. Each match starts where the previous one ended, so matches don't overlap: `regexp_extract_all('aaa', 'aa')` is `['aa']`. | Form | Returns | Example | Result | | --- | --- | --- | --- | | no `group` (or `0`) | each whole match | `regexp_extract_all('a1b22c333', '\d+')` | `['1', '22', '333']` | | `group` 1 or more | that group of each match | `regexp_extract_all('a1b22', '([a-z])(\d+)', 2)` | `['1', '22']` | | with `options` | the same, with flags | `regexp_extract_all('ABab', 'a', 0, 'i')` | `['A', 'a']` | Without a match, the result is an empty list `[]`. A pattern that can match an empty string adds an empty string at each place it matches nothing: `regexp_extract_all('baaac', 'a*')` is `['', 'aaa', '', '']`. To count the matches, take the length of the list. ## NULLs and edge cases | Input | Result | | --- | --- | | A `NULL` string, pattern or group | `NULL` | | A `NULL` options string | Error: `Regex options field must not be NULL` | | `regexp_extract_all('abc', 'x')`, `regexp_extract_all('', 'a')` | `[]` | | `regexp_extract_all('abc', '')` | `['', '', '', '']` | | `regexp_extract_all('', '')` | `['']` | | `regexp_extract_all('ab', '(x)?(b)', 1)` (group 1 doesn't take part) | `[None]`: a list holding `NULL` | | `regexp_extract_all('a1b22', '([a-z])(\d+)', -1)` | `[]` | | `regexp_extract_all('a1b22', '([a-z])(\d+)', 3)` | Error: `Pattern has 2 groups. Cannot access group 3` | | `regexp_extract_all('e\u0301e\u0301', '.')` | four elements: each `e` and each accent | | `regexp_extract_all('abc', '(')` (an invalid pattern) | Error: `Pattern failed to parse, error: 'missing ): ('` | 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-regexp-extract-all#set-up-the-examples): ``` run("SELECT regexp_extract_all(NULL, 'a'), regexp_extract_all('abc', NULL), regexp_extract_all('abc', '(a)', NULL)") run("SELECT regexp_extract_all('abc', 'a', 0, NULL)") run("SELECT regexp_extract_all('abc', 'x'), regexp_extract_all('', 'a'), regexp_extract_all('abc', ''), " "regexp_extract_all('', '')") run("SELECT regexp_extract_all('ab', '(x)?(b)', 1), regexp_extract_all('a1b22', '([a-z])(\\d+)', -1), " "len(regexp_extract_all('e\u0301e\u0301', '.'))") run("SELECT regexp_extract_all('a1b22', '([a-z])(\\d+)', 3)") run("SELECT regexp_extract_all('abc', '(')") ``` ``` [(None, None, None)] InternalError: Invalid Input Error: Regex options field must not be NULL [([], [], ['', '', '', ''], [''])] [([None], [], 4)] OSError: Pattern has 2 groups. Cannot access group 3 OSError: Pattern failed to parse, error: 'missing ): (' ``` ## Examples Every number in each query string, every `id` value (group 2 of `(id)=(\w+)`), and the number of parameters: ``` run(f"SELECT id, regexp_extract_all(query, '\\d+'), regexp_extract_all(query, '(id)=(\\w+)', 2), " f"len(regexp_extract_all(query, '\\w+=')) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, ['17', '42'], ['17', '42'], 3), (2, [], [], 2), (3, [], [], 0), (4, None, None, None)] ``` The `tag` values, in any case, with option `'i'`: ``` run(f"SELECT id, regexp_extract_all(query, 'tag=(\\w+)', 1), regexp_extract_all(query, 'tag=(\\w+)', 1, 'i') " f"FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, [], []), (2, ['vast'], ['SQL', 'vast']), (3, [], []), (4, None, None)] ``` ## 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`). `regexp_extract_all` is always evaluated in the Query Engine: - **In the `SELECT` list,** the scan reads the column and the Query Engine builds a list for each value it returns. - **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step computes `regexp_extract_all()` and keeps the rows that match. ``` plan(f"SELECT id FROM {TABLE} WHERE len(regexp_extract_all(query, '\\w+=')) > 2") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ (len(regexp_extract_all │ │ (query, '\w+=')) > 2) │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ query │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **Test for a match with [regexp_matches](/develop/docs/dev-database-reference-sql-functions-string-regexp-matches),** not with `len(regexp_extract_all(...)) > 0`: it returns a `BOOLEAN` without building a list, and simple patterns are rewritten into cheaper tests. - **Extract at load time.** If you filter on the extracted values often, store them in their own column, such as a `VARCHAR[]`, when you write the data. - **Combine it with a pushed-down condition.** In `id > 100 AND ...`, `id > 100` is still evaluated in VAST DataBase, so the list is built only for the rows that pass it. ## Limitations and errors - **The group must exist in the pattern.** A larger number fails with `Pattern has N groups. Cannot access group M`. A negative group gives `[]`. - **The options string is a constant and isn't `NULL`;** option `g` fails with `Option 'g' (global replace) is only valid for regexp_replace`. - **No `regexp_count`.** It fails with `Scalar Function with name regexp_count does not exist!`. Use `len(regexp_extract_all(s, pattern))`. ``` run("SELECT regexp_extract_all('ABab', 'a', 0, 'g')") run("SELECT regexp_count('abab', 'a')") run("SELECT len(regexp_extract_all('abab', 'a'))") ``` ``` InternalError: Invalid Input Error: Option 'g' (global replace) is only valid for regexp_replace InternalError: Catalog Error: Scalar Function with name regexp_count does not exist! [(2,)] ``` ## Similar functions | Function | Returns | Result for `'a,b,,c'` | | --- | --- | --- | | `regexp_extract_all('a,b,,c', '[^,]+')` | every match: the non-empty fields | `['a', 'b', 'c']` | | [regexp_split_to_array](/develop/docs/dev-database-reference-sql-functions-string-regexp-split-to-array)`('a,b,,c', ',')` | the parts between matches, empty ones included | `['a', 'b', '', 'c']` | | [string_split](/develop/docs/dev-database-reference-sql-functions-string-string-split)`('a,b,,c', ',')` | the parts between literal separators | `['a', 'b', '', 'c']` | | [regexp_extract](/develop/docs/dev-database-reference-sql-functions-string-regexp-extract)`('a,b,,c', '[^,]+')` | the first match only | `'a'` | ``` run("SELECT regexp_extract_all('a,b,,c', '[^,]+'), regexp_split_to_array('a,b,,c', ','), " "string_split('a,b,,c', ','), regexp_extract('a,b,,c', '[^,]+')") ``` ``` [(['a', 'b', 'c'], ['a', 'b', '', 'c'], ['a', 'b', '', 'c'], 'a')] ``` Clean up: ``` run(f"DROP TABLE IF EXISTS {TABLE}") run(f"DROP SCHEMA IF EXISTS {SCHEMA}") conn.close() ``` ``` [] [] ``` ## See also - [Regular-expression syntax and options](/develop/docs/dev-database-reference-sql-functions-string-regexp-syntax). - [Regular expressions](/develop/docs/dev-database-reference-sql-functions-string-regular-expressions): all the regular-expression 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.