---
title: "signbit"
slug: "dev-database-reference-sql-functions-binary-hash-uuid-signbit"
updated: 2026-10-30T18:18:56Z
published: 2026-10-30T18:18:56Z
canonical: "docs.vastdata.com/dev-database-reference-sql-functions-binary-hash-uuid-signbit"
---

> ## 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.

# signbit

*Applies to VAST Cluster 5.5.*

*[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [Binary, hash and UUID functions](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid) › Bits of numbers.* Returns `true` when the sign bit of a floating-point number is set. Unlike a test such as `x < 0`, it tells `-0.0` from `0.0`, and it reads the sign of infinities and NaN: `signbit(-0.0::DOUBLE)` is `true`.

## Syntax

```
signbit(x)
```

| Argument | Type | Description |
| --- | --- | --- |
| `x` | `DOUBLE` or `FLOAT` (integers and decimals are converted) | The number to test. |

**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_binary_hash_uuid_signbit`. 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 sensor readings, each as a `DOUBLE` and as a `DECIMAL`. Reading 2 is a negative zero in the `DOUBLE` column, and the third 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_binary_hash_uuid_signbit"'

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, "<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, amount DECIMAL(10,2))")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, 2.5, 2.50), "
    "(2, '-0.0'::DOUBLE, 0.00), "
    "(3, NULL, NULL), "
    "(4, -2.5, -2.50)")
```

```
[]
[]
[(4,)]
```

## What it does

A floating-point number stores its sign in one bit, separately from its value. `signbit` returns that bit:

| Value | `x &lt; 0` | `signbit(x)` |
| --- | --- | --- |
| `-2.5` | `true` | `true` |
| `-0.0` | `false` | `true` |
| `0.0` | `false` | `false` |
| `&apos;-inf&apos;::DOUBLE` |  | `true` |
| `&apos;nan&apos;::DOUBLE` |  | `false` |
| `&apos;-nan&apos;::DOUBLE` |  | `true` |

An integer or a `DECIMAL` is accepted too: `signbit` is `true` for negative values and `false` for zero. A `DECIMAL` has no negative zero: `-0.0` written as a literal is a `DECIMAL`, so `signbit(-0.0)` is `false`. Write `-0.0::DOUBLE` or `&apos;-0.0&apos;::DOUBLE` for the floating-point value.

## NULLs and edge cases

| Input | Result |
| --- | --- |
| `NULL` | `NULL` |
| `-0.0::DOUBLE`, `&apos;-0.0&apos;::FLOAT` | `true` |
| `-0.0` (a `DECIMAL` literal) | `false` |
| `0.0 * -1` (`DECIMAL`) | `false` |
| `-0.0::DOUBLE * 1` | `true` |
| `&apos;inf&apos;::DOUBLE`, `&apos;-inf&apos;::DOUBLE` | `false`, `true` |
| `&apos;nan&apos;::DOUBLE`, `&apos;-nan&apos;::DOUBLE` | `false`, `true` |
| `-2`, `-1::TINYINT`, `-2.50::DECIMAL(5,2)` | `true` |
| `0` | `false` |
| `signbit(&apos;-1&apos;)` (a string literal) | Error: `Could not choose a best candidate function for the function call &quot;signbit(STRING_LITERAL)&quot;` |

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-binary-hash-uuid-signbit#set-up-the-examples):

```
run("SELECT signbit(NULL), signbit(-0.0::DOUBLE), signbit('-0.0'::FLOAT), signbit(-0.0), signbit(0.0 * -1), "
    "signbit(-0.0::DOUBLE * 1)")
run("SELECT signbit('inf'::DOUBLE), signbit('-inf'::DOUBLE), signbit('nan'::DOUBLE), signbit('-nan'::DOUBLE), "
    "signbit(-2), signbit(-1::TINYINT), signbit(-2.50::DECIMAL(5,2)), signbit(0)")
run("SELECT signbit('-1')")
```

```
[(None, True, True, False, False, True)]
[(False, True, False, True, True, True, True, False)]
InternalError: Binder Error: Could not choose a best candidate function for the function call "signbit(STRING_LITERAL)". In order to select one, please add explicit type casts.
```

## Examples

The sign bit of each reading, compared with `x &lt; 0`. Reading 2 is a negative zero, so only `signbit` sees its sign; its `DECIMAL` copy is a plain zero:

```
run(f"SELECT id, x, x < 0, signbit(x), amount, signbit(amount) FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, 2.5, False, False, Decimal('2.50'), False), (2, -0.0, False, True, Decimal('0.00'), False), (3, None, None, None, None, None), (4, -2.5, True, True, Decimal('-2.50'), True)]
```

Keep the readings whose sign bit is set, including the negative zero:

```
run(f"SELECT id, x FROM {TABLE} WHERE signbit(x) ORDER BY id LIMIT 10")
```

```
[(2, -0.0), (4, -2.5)]
```

## 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 `signbit()` is always computed by the Query Engine:

- **In the `SELECT` list,** the scan reads the column and the Query Engine computes `signbit()` for each row it returns.
- **In `WHERE`,** the scan sends the column for every row, and a `FILTER` step in the Query Engine computes `signbit()` 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 signbit(x)")
```

```
┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│         signbit(x)        │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             x             │
│             id            │
│                           │
└───────────────────────────┘
```

## Make it faster

- **Use `x &lt; 0` when negative zero doesn't matter.** A comparison of the raw column with a constant is pushed down to VAST DataBase, so rows that don't match never leave storage. It misses `-0.0`, which `signbit(x)` finds. The plan has no `FILTER` step:

```
plan(f"SELECT id FROM {TABLE} WHERE x < 0")
```

```
┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
```

- **Combine it with a pushed-down condition.** In `x &lt;= 0 AND signbit(x)`, `x &lt;= 0` is evaluated in VAST DataBase, so `signbit()` runs only on the rows that pass it: the negative values and both zeros.

## Limitations and errors

- **Numbers only.** A string literal fails with `Could not choose a best candidate function`, and a `BLOB`, date, boolean or list fails with `No function matches the given name and argument types`. The error lists the types `signbit` accepts: `signbit(FLOAT)` and `signbit(DOUBLE)`. Cast a string to `DOUBLE` first.

```
run("SELECT signbit(true)")
run("SELECT signbit('-1'::DOUBLE)")
```

```
InternalError: Binder Error: No function matches the given name and argument types 'signbit(BOOLEAN)'. You might need to add explicit type casts.
[(True,)]
```

- **No negative zero in `DECIMAL` or integer columns.** Only `FLOAT` and `DOUBLE` values have one. A `DECIMAL` zero, and a `DECIMAL` expression such as `0.0 * -1`, have `signbit` `false`.

## Similar functions

| Function | Result for `-0.0::DOUBLE` | Result for `-2.5::DOUBLE` |
| --- | --- | --- |
| `signbit(x)` | `true` | `true` |
| [sign](/develop/docs/dev-database-reference-sql-functions-numeric-sign)`(x)`: -1, 0 or 1 | `0` | `-1` |
| `x &lt; 0` | `false` | `true` |

```
run("SELECT signbit(-0.0::DOUBLE), sign(-0.0::DOUBLE), -0.0::DOUBLE < 0, signbit(-2.5::DOUBLE), sign(-2.5::DOUBLE), "
    "-2.5::DOUBLE < 0")
```

```
[(True, 0, False, True, -1, True)]
```

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-sign): `sign` and `signbit` with the other sign and rounding functions.
- [Binary, hash and UUID functions](/develop/docs/dev-database-reference-sql-functions-binary-hash-uuid): the bit string functions.
- [Where filters run](/develop/docs/dev-database-reference-sql-select#where-filters-run) and [pushdowns](/develop/docs/dev-database-reference-pushdowns).