--- title: "strpos" slug: "dev-database-reference-sql-functions-string-strpos" updated: 2026-10-30T18:18:56Z published: 2026-10-30T18:18:56Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-string-strpos" --- > ## 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. # strpos *Applies to VAST Cluster 5.5.* *[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Search and split](/develop/docs/dev-database-reference-sql-functions-string-search-and-split) › Searching.* Returns the position of the first occurrence of a substring in a string, counting characters from 1, or 0 if it doesn't occur. `instr` is the same function, and `position(substring IN s)` is the standard SQL form, with the arguments the other way round. ## Syntax ``` strpos(s, substring) instr(s, substring) position(substring IN s) ``` | Argument | Type | Description | | --- | --- | --- | | `s` | `VARCHAR` | The string to search. | | `substring` | `VARCHAR` | The text to look for. | **Returns:** `BIGINT`: the position of the first character of the first match, counting from 1, or 0 if there's no match. **Aliases:** `instr`, `position(substring IN s)`. ## 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_strpos`. 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 users with an e-mail address and a file path. Row 3 has an accented name. 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_strpos"' 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}.users" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, email VARCHAR, home VARCHAR)") run(f"INSERT INTO {TABLE} VALUES " "(1, 'ada@example.com', '/home/ada'), " "(2, 'grace.hopper@example.org', '/home/grace/db'), " "(3, 'jos\u00e9@example.es', '/home/jose'), " "(4, NULL, NULL)") ``` ``` [] [] [(4,)] ``` ## What it does `strpos(s, substring)` scans `s` from the left and returns where `substring` first starts: - **Positions count characters (code points) from 1,** not bytes. In `'café x'`, `x` is at position 6, although `é` takes two bytes. A letter written with a combining accent (`e` followed by U+0301) counts as two. - **The first match wins,** and matches can overlap: `strpos('aaa', 'aa')` is 1, and `strpos('abcabc', 'c')` is 3. - **No match gives 0,** never `NULL` (unless an argument is `NULL`). Test `strpos(s, substring) > 0` for "contains". - **An empty substring gives 1,** even in an empty string. - **Case and accents must match exactly,** as in [contains](/develop/docs/dev-database-reference-sql-functions-string-contains): `strpos('ABC', 'b')` is 0. `position(substring IN s)` takes the substring first; `strpos` and `instr` take the string first. ## NULLs and edge cases | Input | Result | | --- | --- | | `strpos(NULL, 'o')`, `strpos('abc', NULL)` | `NULL` | | `position(NULL IN 'abc')`, `position('b' IN NULL)` | `NULL` | | `strpos('abc', '')`, `strpos('', '')` | `1` | | `strpos('', 'a')`, `strpos('abc', 'x')` | `0` | | `strpos('abc', 'abcd')` | `0` | | `strpos('ABC', 'b')` | `0` | | `strpos('aaa', 'aa')` | `1` | | `strpos('abcabc', 'c')` | `3` | | `strpos('café x', 'x')` | `6` | | `strpos('e\u0301x', 'x')` (`e` and a combining accent) | `3` | | `strpos('🇫🇷x', 'x')` (a flag emoji is two code points) | `3` | | `strpos('cafe\u0301', 'é')` (decomposed string, precomposed substring) | `0` | | A number, date, boolean, `BLOB` or list on either side | 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-strpos#set-up-the-examples): ``` run("SELECT strpos(NULL, 'o'), strpos('abc', NULL), position(NULL IN 'abc'), position('b' IN NULL)") run("SELECT strpos('abc', ''), strpos('', ''), strpos('', 'a'), strpos('abc', 'x'), strpos('abc', 'abcd'), " "strpos('ABC', 'b'), strpos('aaa', 'aa'), strpos('abcabc', 'c')") run("SELECT strpos('caf\u00e9 x', 'x'), strpos('e\u0301x', 'x'), strpos('\U0001F1EB\U0001F1F7x', 'x'), " "strpos('cafe\u0301', '\u00e9')") run("SELECT strpos(123, 'o')") ``` ``` [(None, None, None, None)] [(1, 1, 0, 0, 0, 0, 1, 3)] [(6, 3, 3, 0)] InternalError: Binder Error: No function matches the given name and argument types 'strpos(INTEGER_LITERAL, STRING_LITERAL)'. You might need to add explicit type casts. ``` ## Examples Find the `@` in each e-mail address with all three spellings. In row 3, `é` counts as one character: ``` run(f"SELECT id, strpos(email, '@'), instr(email, '@'), position('@' IN email) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, 4, 4, 4), (2, 13, 13, 13), (3, 5, 5, 5), (4, None, None, None)] ``` Take the user name before the `@`, with [substring](/develop/docs/dev-database-reference-sql-functions-string-substring): ``` run(f"SELECT id, substring(email, 1, strpos(email, '@') - 1) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, 'ada'), (2, 'grace.hopper'), (3, 'josé'), (4, None)] ``` Keep the users whose home directory has a subdirectory called `db`: ``` run(f"SELECT id, home FROM {TABLE} WHERE strpos(home, '/db') > 0 ORDER BY id LIMIT 10") ``` ``` [(2, '/home/grace/db')] ``` ## 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 `strpos()` is always computed by the Query Engine: - **In the `SELECT` list,** the scan reads the column and the Query Engine computes `strpos()` for each row it returns. - **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `strpos()` and keeps the rows that match. No rows are skipped in storage. `position(substring IN s)` appears in the plan as `"position"(s, substring)`. The plan of the `WHERE` example shows the `FILTER` step above the scan: ``` plan(f"SELECT id FROM {TABLE} WHERE strpos(home, '/db') > 0") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ (strpos(home, '/db') > 0) │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ home │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **To test whether a string contains a substring, `contains()` says what you mean.** `strpos(s, x) > 0` and [contains](/develop/docs/dev-database-reference-sql-functions-string-contains)`(s, x)` both run in the `FILTER` step; `LIKE '%x%'` is rewritten to `contains()`. - **Store the part you filter on.** If you often split a value at a separator to filter on one part, such as the domain of an e-mail address, write that part to its own column when you load the rows: `domain = 'example.org'` is pushed down to VAST DataBase. The plan for a raw column compared with a constant has no `FILTER` step: ``` plan(f"SELECT id FROM {TABLE} WHERE email = 'ada@example.com'") ``` ``` ┌───────────────────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ Projections: id │ │ │ └───────────────────────────┘ ``` - **Combine it with a pushed-down condition.** In `id > 1 AND strpos(home, '/db') > 0`, `id > 1` is still evaluated in VAST DataBase, so `strpos()` runs only on the rows that pass it. ## Limitations and errors - **Strings only.** A number, a date, a boolean, a `BLOB` or a list on either side fails with `No function matches the given name and argument types`, for example `'strpos(INTEGER_LITERAL, STRING_LITERAL)'`. Cast the value to `VARCHAR` first. - **No start position.** `strpos(s, substring, start)` fails with `No function matches the given name and argument types`, and `position(substring IN s FROM start)` is a syntax error. - **`position` takes `IN`, not a comma.** `position('abc', 'b')` fails with `Parser Error: syntax error at or near ","`. - **Other SQL dialects' names aren't available.** `locate`, `charindex` and `strrpos` (the last occurrence) fail with `Scalar Function with name ... does not exist!`. ``` run("SELECT strpos('abab', 'b', 3)") run("SELECT position('abc', 'b')") run("SELECT locate('b', 'abc')") run("SELECT strpos(CAST(2026 AS VARCHAR), '2')") ``` ``` InternalError: Binder Error: No function matches the given name and argument types 'strpos(STRING_LITERAL, STRING_LITERAL, INTEGER_LITERAL)'. You might need to add explicit type casts. InternalError: Parse query: 'SELECT position('abc', 'b')' failed with: Parser Error: syntax error at or near "," InternalError: Catalog Error: Scalar Function with name locate does not exist! [(1,)] ``` ## Similar functions | Function | Returns | Result for `'Hello World'` and `'o'` | | --- | --- | --- | | `strpos`, `instr`, `position('o' IN s)` | the first position, in characters | `5` | | [contains](/develop/docs/dev-database-reference-sql-functions-string-contains) | whether it occurs | `true` | | [starts_with](/develop/docs/dev-database-reference-sql-functions-string-starts-with) | whether the string begins with it | `false` | | [strlen](/develop/docs/dev-database-reference-sql-functions-string-strlen) | bytes, not characters: use it to see where a position in bytes differs | | | [split_part](/develop/docs/dev-database-reference-sql-functions-string-split-part) | the text between separators, by number | | | [regexp_extract](/develop/docs/dev-database-reference-sql-functions-string-regexp-extract) | the text that matches a pattern | | ``` run("SELECT strpos('Hello World', 'o'), instr('Hello World', 'o'), position('o' IN 'Hello World'), " "contains('Hello World', 'o'), starts_with('Hello World', 'o')") run("SELECT strpos('caf\u00e9 x', 'x'), strlen('caf\u00e9 '), length('caf\u00e9 ')") ``` ``` [(5, 5, 5, True, False)] [(6, 6, 5)] ``` Clean up: ``` run(f"DROP TABLE IF EXISTS {TABLE}") run(f"DROP SCHEMA IF EXISTS {SCHEMA}") conn.close() ``` ``` [] [] ``` ## See also - [Search and split](/develop/docs/dev-database-reference-sql-functions-string-search-and-split): all the search 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.