--- title: "isnan" slug: "dev-database-reference-sql-functions-numeric-isnan" updated: 2026-10-30T18:18:51Z published: 2026-10-30T18:18:51Z canonical: "docs.vastdata.com/dev-database-reference-sql-functions-numeric-isnan" --- > ## 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. # isnan *Applies to VAST Cluster 5.5.* *[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Numeric and math functions](/develop/docs/dev-database-reference-sql-functions-numeric) › Floating-point values.* Returns `true` if `x` is NaN (not a number), the floating-point value that results from operations such as `0 / 0`, and `false` for any other number. ## Syntax ``` isnan(x) ``` | Argument | Type | Description | | --- | --- | --- | | `x` | `DOUBLE` or `FLOAT` | The value to test. An integer or `DECIMAL` literal is accepted, and is never NaN. | **Returns:** `BOOLEAN`. ## 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_numeric_isnan`. 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 seven sensor readings: ordinary values, NaN, both infinities, negative zero and, in row 6, no value: ``` 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_numeric_isnan"' 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}.readings" run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}") run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, x DOUBLE)") run(f"INSERT INTO {TABLE} VALUES " "(1, 2.5), (2, 'nan'::DOUBLE), (3, 'inf'::DOUBLE), (4, '-inf'::DOUBLE), " "(5, '-0.0'::DOUBLE), (6, NULL), (7, 1.0)") ``` ``` [] [] [(7,)] ``` ## What it does NaN is a special floating-point value, separate from NULL. You get it from operations with no numeric answer, such as `0 / 0`, `fmod(1, 0)` or `pow(-27, 1.0 / 3)`, and you can write it as `'nan'::DOUBLE` (or `'NaN'::DOUBLE`). `isnan(x)` is `true` only for NaN: infinity, negative zero and every ordinary number give `false`, and NULL gives NULL. In the VAST Query Engine, NaN compares as a value of its own, larger than any other number: | Comparison | Result | | --- | --- | | `'nan'::DOUBLE = 'nan'::DOUBLE` | `true` | | `'nan'::DOUBLE <> 'nan'::DOUBLE` | `false` | | `'nan'::DOUBLE > 1e308` | `true` | | `'nan'::DOUBLE > 'inf'::DOUBLE` | `true` | So `max()` of a column that holds a NaN is NaN, and a sum that includes one is NaN. Exclude NaN with `NOT isnan(x)` when you aggregate (see [Examples](/develop/docs/dev-database-reference-sql-functions-numeric-isnan#examples)). ``` run("SELECT 'nan'::DOUBLE = 'nan'::DOUBLE, 'nan'::DOUBLE <> 'nan'::DOUBLE, " "'nan'::DOUBLE > 1e308, 'nan'::DOUBLE > 'inf'::DOUBLE") ``` ``` [(True, False, True, True)] ``` ## NULLs and edge cases | Input | Result | | --- | --- | | `NULL`, `NULL::FLOAT` | `NULL`: NULL isn't NaN | | `'nan'::DOUBLE`, `'nan'::FLOAT` | `true` | | `0 / 0` | `true` | | `'inf'::DOUBLE`, `'-inf'::DOUBLE`, `1 / 0`, `1e308 * 10` | `false` | | `-0.0::DOUBLE`, `1.0::DOUBLE`, `1::FLOAT` | `false` | | `1`, `2.45`, `9223372036854775807` (integer and `DECIMAL` literals) | `false` | | `'nan'` or any other string literal | Error: `Could not choose a best candidate function for the function call "isnan(STRING_LITERAL)"`; cast it: `'nan'::DOUBLE` | | A date, timestamp, `BLOB`, boolean, list or interval | Error: `No function matches the given name and argument types`, for example `'isnan(DATE)'` | 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-numeric-isnan#set-up-the-examples): ``` run("SELECT isnan(NULL), isnan(NULL::FLOAT), isnan('nan'::DOUBLE), isnan('nan'::FLOAT), isnan(0 / 0)") run("SELECT isnan('inf'::DOUBLE), isnan('-inf'::DOUBLE), isnan(1 / 0), isnan(1e308 * 10)") run("SELECT isnan(-0.0::DOUBLE), isnan(1.0::DOUBLE), isnan(1::FLOAT), isnan(1), isnan(2.45), " "isnan(9223372036854775807), typeof(isnan(1))") run("SELECT isnan('nan')") run("SELECT isnan(DATE '2026-10-16')") ``` ``` [(None, None, True, True, True)] [(False, False, False, False)] [(False, False, False, False, False, False, 'BOOLEAN')] InternalError: Binder Error: Could not choose a best candidate function for the function call "isnan(STRING_LITERAL)". In order to select one, please add explicit type casts. InternalError: Binder Error: No function matches the given name and argument types 'isnan(DATE)'. You might need to add explicit type casts. ``` ## Examples Test each reading. Row 6 has no value, so its result is NULL: ``` run(f"SELECT id, x, isnan(x) FROM {TABLE} ORDER BY id LIMIT 10") ``` ``` [(1, 2.5, False), (2, nan, True), (3, inf, False), (4, -inf, False), (5, -0.0, False), (6, None, None), (7, 1.0, False)] ``` Find the NaN readings: ``` run(f"SELECT id FROM {TABLE} WHERE isnan(x) ORDER BY id LIMIT 10") ``` ``` [(2,)] ``` Aggregate with and without the NaN reading. With it, `max()` and `sum()` are NaN. Without it, `max()` is `inf`, but `sum()` is still NaN, because the column also holds `inf` and `-inf`, and their sum is NaN; to leave out the infinities too, use [isfinite](/develop/docs/dev-database-reference-sql-functions-numeric-isfinite): ``` run(f"SELECT min(x), max(x), sum(x), count(x) FROM {TABLE}") run(f"SELECT min(x), max(x), sum(x), count(x) FROM {TABLE} WHERE NOT isnan(x)") ``` ``` [(-inf, nan, nan, 6)] [(-inf, inf, nan, 5)] ``` ## 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 `isnan()` is always computed by the Query Engine: - **In the `SELECT` list,** the scan reads the column and the Query Engine computes `isnan()` for each row it returns. - **In `WHERE`,** `isnan(x)` and `NOT isnan(x)` alike, the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `isnan()` and keeps the rows that match. The plan of the `WHERE` example shows the `FILTER` step above the scan: ``` plan(f"SELECT id FROM {TABLE} WHERE isnan(x)") ``` ``` ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ #1 │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ FILTER │ │ ──────────────────── │ │ isnan(x) │ │ │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ │ │ Projections: │ │ x │ │ id │ │ │ └───────────────────────────┘ ``` ## Make it faster - **Compare with NaN directly.** `x = 'nan'::DOUBLE` is a comparison of the raw column with a constant, so it's pushed down to VAST DataBase and the plan has no `FILTER` step. The second line shows the rows it returns: ``` plan(f"SELECT id FROM {TABLE} WHERE x = 'nan'::DOUBLE") run(f"SELECT id FROM {TABLE} WHERE x = 'nan'::DOUBLE ORDER BY id LIMIT 10") ``` ``` ┌───────────────────────────┐ │ VAST_SCAN │ │ ──────────────────── │ │ Function: VAST_SCAN │ │ Projections: id │ │ │ └───────────────────────────┘ [(2,)] ``` - **Store NULL for a missing value, not NaN.** Aggregates skip NULLs (`count(x)` above doesn't count row 6) but not NaN, so a NULL keeps `max()` and `sum()` meaningful without a filter. ## Limitations and errors - **Floating-point values only.** The function takes `DOUBLE` and `FLOAT`. A date, timestamp, `BLOB`, boolean, list or interval fails with `No function matches the given name and argument types`. For the special date values `'infinity'` and `'-infinity'`, use [isinf](/develop/docs/dev-database-reference-sql-functions-numeric-isinf) or [isfinite](/develop/docs/dev-database-reference-sql-functions-numeric-isfinite). - **A string literal must be cast.** `isnan('nan')` fails with `Could not choose a best candidate function for the function call "isnan(STRING_LITERAL)"`, because the literal could be a `DOUBLE` or a `FLOAT`. Write `isnan('nan'::DOUBLE)`. - **Other names aren't available.** `is_nan()` and a `nan()` constant don't exist (`Scalar Function with name is_nan does not exist!`); use `isnan()` and `'nan'::DOUBLE`: ``` run("SELECT is_nan(1.0)") run("SELECT nan()") run("SELECT 'nan'::DOUBLE, 'NaN'::DOUBLE") ``` ``` InternalError: Catalog Error: Scalar Function with name is_nan does not exist! InternalError: Catalog Error: Scalar Function with name nan does not exist! [(nan, nan)] ``` ## Similar functions | Function | `nan` | `inf` | `-inf` | `-0.0` | `1.0` | `NULL` | | --- | --- | --- | --- | --- | --- | --- | | `isnan(x)` | `true` | `false` | `false` | `false` | `false` | `NULL` | | [isinf](/develop/docs/dev-database-reference-sql-functions-numeric-isinf)`(x)` | `false` | `true` | `true` | `false` | `false` | `NULL` | | [isfinite](/develop/docs/dev-database-reference-sql-functions-numeric-isfinite)`(x)` | `false` | `false` | `false` | `true` | `true` | `NULL` | | [signbit](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid-signbit)`(x)` | `false` | `false` | `true` | `true` | `false` | `NULL` | ``` run("SELECT x, isnan(x), isinf(x), isfinite(x), signbit(x) FROM (VALUES ('nan'::DOUBLE), ('inf'::DOUBLE), " "('-inf'::DOUBLE), (-0.0::DOUBLE), (1.0::DOUBLE), (NULL::DOUBLE)) v(x)") ``` ``` [(nan, True, False, False, False), (inf, False, True, False, False), (-inf, False, True, False, True), (-0.0, False, False, True, True), (1.0, False, False, True, False), (None, None, None, None, None)] ``` Clean up: ``` run(f"DROP TABLE IF EXISTS {TABLE}") run(f"DROP SCHEMA IF EXISTS {SCHEMA}") conn.close() ``` ``` [] [] ``` ## See also - [Numeric and math functions](/develop/docs/dev-database-reference-sql-functions-numeric#floating-point-values): isnan, isinf and isfinite. - [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.