--- title: "regexp_escape" slug: "dev-database-reference-sql-functions-string-regexp-escape" updated: 2026-10-30T18:18:56Z published: 2026-10-30T18:18:56Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-string-regexp-escape" --- > ## 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_escape *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.* Puts a backslash in front of every character of a string that could have a meaning in a regular expression, so the result matches the original text literally. Use it to build a pattern from a search term, a column value or user input. ## Syntax ``` regexp_escape(s) ``` | Argument | Type | Description | | --- | --- | --- | | `s` | `VARCHAR` | The text to escape. | **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_escape`. 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 search terms and the text to search. 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_escape"' 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}.terms" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, term VARCHAR, body VARCHAR)") run(f"INSERT INTO {TABLE} VALUES " "(1, 'a.b', 'see axb'), " "(2, '1+1', '1+1=2'), " "(3, 'price (USD)', 'Total price (USD): 42'), " "(4, '50%', 'up 50% today'), " "(5, NULL, NULL)") ``` ``` [] [] [(5,)] ``` ## What it does In a regular expression, characters such as `.`, `+`, `(` and `*` have a meaning: `a.b` matches `axb` as well as `a.b`. `regexp_escape` puts a backslash in front of each of them, so `regexp_escape('a.b')` returns `a\.b`, which matches only the text `a.b`. It escapes every ASCII character that isn't a letter, a digit or an underscore, including the space, `%`, `-`, `#`, `:`, `/`, a newline and a tab. Letters, digits, `_` and non-ASCII characters (such as `é` or an emoji) are returned unchanged. The escaped string is a pattern that matches the original string: `regexp_full_match(s, regexp_escape(s))` is true. ## NULLs and edge cases | Input | Result | | --- | --- | | `NULL` | `NULL` | | `''` (empty string) | `''` | | `'a b'` | `a\ b`: the space is escaped | | `'a_b%c'` | `a_b\%c`: `_` is kept, `%` is escaped | | `'é'`, an emoji | Unchanged | | `'a#b'`, `'a:b'` | `a\#b`, `a\:b` | | A newline or a tab | A backslash, then the newline or tab | | `'.^$*+?()[]{}\\|-/'` | Every character escaped | | A number, date, boolean, `BLOB` or list | Error: `No function matches the given name and argument types`; cast to `VARCHAR` first | The same cases, as the cluster returns them. They use the table and helpers from [Set up the examples](/develop/docs/dev-database-reference-sql-functions-string-regexp-escape#set-up-the-examples): ``` run("SELECT regexp_escape(NULL), regexp_escape(''), regexp_escape('a b'), regexp_escape('a_b%c'), " "regexp_escape('\u00e9'), regexp_escape('\U0001F600'), regexp_escape('a#b'), regexp_escape('a:b')") run("SELECT regexp_escape('a\nb'), regexp_escape('a\tb')") run("SELECT regexp_escape('.^$*+?()[]{}|-/')") run("SELECT regexp_escape(123)") ``` ``` [(None, '', 'a\\ b', 'a_b\\%c', 'é', '😀', 'a\\#b', 'a\\:b')] [('a\\\nb', 'a\\\tb')] [('\\.\\^\\$\\*\\+\\?\\(\\)\\[\\]\\{\\}\\|\\-\\/',)] InternalError: Binder Error: No function matches the given name and argument types 'regexp_escape(INTEGER_LITERAL)'. You might need to add explicit type casts. ``` ## Examples Each term, escaped: ``` run(f"SELECT id, term, regexp_escape(term) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, 'a.b', 'a\\.b'), (2, '1+1', '1\\+1'), (3, 'price (USD)', 'price\\ \\(USD\\)'), (4, '50%', '50\\%'), (5, None, None)] ``` Search each row's text for its term, first as a pattern and then escaped. Used as a pattern, each term's `.`, `+`, `(` and `)` keep their meaning; escaped, each term matches only its own text: ``` run(f"SELECT id, regexp_matches(body, term), regexp_matches(body, regexp_escape(term)) " f"FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, True, False), (2, False, True), (3, False, True), (4, True, True), (5, None, None)] ``` Use the escaped text inside a larger pattern. Here it replaces the literal text `1+1`: ``` run("SELECT regexp_replace('1+1=2', regexp_escape('1+1'), 'two'), " "regexp_full_match('a.b*(c)', regexp_escape('a.b*(c)'))") ``` ``` [('two=2', True)] ``` Keep the rows whose text contains `(USD)`: ``` run(f"SELECT id, body FROM {TABLE} WHERE regexp_matches(body, regexp_escape('(USD)')) ORDER BY id LIMIT 10") ``` ``` [(3, 'Total price (USD): 42')] ``` ## 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 regular-expression match is a function of a column, so it's computed by the Query Engine: - **In the `SELECT` list,** the scan reads the column and the Query Engine computes `regexp_escape()` for each row it returns. - **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine runs the match and keeps the rows that pass. The plan of the `WHERE` example shows the `FILTER` step above the scan. The argument is a constant, so the escaped text is worked out when the query is planned, and the match is rewritten into a `contains()` test, as for a plain literal pattern ([regexp_matches](/develop/docs/dev-database-reference-sql-functions-string-regexp-matches#how-it-runs-in-vast)): ``` plan(f"SELECT id FROM {TABLE} WHERE regexp_matches(body, regexp_escape('(USD)'))") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ contains(body, '(USD)') │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ body │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **For a fixed search text, don't use a pattern at all.** `contains(body, '(USD)')` finds literal text without a regular expression, and option `'l'` makes [regexp_matches](/develop/docs/dev-database-reference-sql-functions-string-regexp-matches) treat its whole pattern as literal text. Use `regexp_escape` when only part of the pattern is literal, or when the pattern comes from a column. - **Combine it with a pushed-down condition.** In `id > 100 AND regexp_matches(...)`, the comparison of the raw column with a constant can be evaluated in VAST DataBase, so the match runs only on the rows that pass it. See [pushdowns](/develop/docs/dev-database-reference-pushdowns). ## Limitations and errors - **`VARCHAR` only.** A number, a date, a boolean, a `BLOB` or a list fails with `No function matches the given name and argument types`, for example `'regexp_escape(INTEGER_LITERAL)'`. Cast the value to `VARCHAR` first. - **It escapes for regular expressions, not for `LIKE`.** `_` is left as it is. To match a literal `%` or `_` with `LIKE`, see [like_escape](/develop/docs/dev-database-reference-sql-functions-string-like-escape). ## Similar functions | Function | Use it to | `'a.b'` matched against `'axb'` | | --- | --- | --- | | `regexp_escape` with [regexp_matches](/develop/docs/dev-database-reference-sql-functions-string-regexp-matches) | Match literal text inside a larger pattern | `false` | | [regexp_matches](/develop/docs/dev-database-reference-sql-functions-string-regexp-matches) with option `'l'` | Match the whole pattern as literal text | `false` | | [regexp_matches](/develop/docs/dev-database-reference-sql-functions-string-regexp-matches) without escaping | Match a pattern: `.` matches any character | `true` | | [contains](/develop/docs/dev-database-reference-sql-functions-string-contains) | Find literal text without a regular expression | `false` | ``` run("SELECT regexp_matches('axb', regexp_escape('a.b')), regexp_matches('axb', 'a.b', 'l'), " "regexp_matches('axb', 'a.b'), contains('axb', 'a.b')") ``` ``` [(False, False, True, False)] ``` Clean up: ``` run(f"DROP TABLE IF EXISTS {TABLE}") run(f"DROP SCHEMA IF EXISTS {SCHEMA}") conn.close() ``` ``` [] [] ``` ## See also - [Regular expressions](/develop/docs/dev-database-reference-sql-functions-string-regular-expressions): all the regular-expression functions. - [Regular expression syntax](/develop/docs/dev-database-reference-sql-functions-string-regexp-syntax). - [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.