isinf

Applies to VAST Cluster 5.5.

Functions › Numeric and math functions › Floating-point values. Returns true if x is infinite, inf or -inf, and false for any other number, NaN included. It also takes a date or timestamp, and is true for the special values 'infinity' and '-infinity'.

Syntax

isinf(x)

Returns: BOOLEAN.

Set up the examples

The examples connect with the ADBC driver, as in VAST Query Engine (ADBC), and work in a schema called docs_sql_fn_numeric_isinf. Set QE_ENDPOINT, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY and VASTDB_BUCKET (SQL reference), 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 ratios: ordinary values, both infinities, NaN, 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_isinf"'

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}.ratios"
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, 'inf'::DOUBLE), (3, '-inf'::DOUBLE), (4, 'nan'::DOUBLE), "
    "(5, '-0.0'::DOUBLE), (6, NULL), (7, 1.0)")

[]
[]
[(7,)]

What it does

Floating-point values include positive and negative infinity. You get them from a division by zero with / (1 / 0 is inf), from a result too large for the type (1e308 * 10 is inf), and by casting 'inf', 'infinity' or '-Infinity' to DOUBLE. isinf(x) is true for both infinities and false for everything else, NaN included; NULL gives NULL.

A DATE or TIMESTAMP can also hold 'infinity' or '-infinity', and isinf() is true for them and false for an ordinary date. The date and time version has the details.

NULLs and edge cases

The same cases, as the cluster returns them. They use the table and helpers from Set up the examples:

run("SELECT isinf(NULL), isinf(NULL::FLOAT), isinf('inf'::DOUBLE), isinf('-inf'::DOUBLE), isinf('inf'::FLOAT)")
run("SELECT isinf(1 / 0), isinf(-1 / 0), isinf(1e308 * 10), isinf('nan'::DOUBLE), isinf('nan'::FLOAT), isinf(0 / 0)")
run("SELECT isinf(-0.0::DOUBLE), isinf(1.0::DOUBLE), isinf(1::FLOAT), isinf(1), isinf(2.45), "
    "isinf(9223372036854775807), typeof(isinf(1))")
run("SELECT isinf('infinity'::DATE), isinf('infinity'::TIMESTAMP), isinf(DATE '2026-10-16')")
run("SELECT isinf('nan')")
run("SELECT isinf(true)")

[(None, None, True, True, True)]
[(True, True, True, False, False, False)]
[(False, False, False, False, False, False, 'BOOLEAN')]
[(True, True, False)]
InternalError: Binder Error: Could not choose a best candidate function for the function call "isinf(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'isinf(BOOLEAN)'. You might need to add explicit type casts.

Examples

Test each ratio. Row 4 is NaN, so its result is false; row 6 has no value, so its result is NULL:

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

[(1, 2.5, False), (2, inf, True), (3, -inf, True), (4, nan, False), (5, -0.0, False), (6, None, None), (7, 1.0, False)]

Replace the infinite ratios with NULL before you compute with them:

run(f"SELECT id, CASE WHEN isinf(x) THEN NULL ELSE x END FROM {TABLE} ORDER BY id LIMIT 10")

[(1, 2.5), (2, None), (3, None), (4, nan), (5, -0.0), (6, None), (7, 1.0)]

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 isinf() is always computed by the Query Engine:

• In the SELECT list, the scan reads the column and the Query Engine computes isinf() for each row it returns.
• In WHERE, the scan sends the column for every row, and a FILTER step in the Query Engine computes isinf() and keeps the rows that match.

The plan of a WHERE isinf(x) query shows the FILTER step above the scan:

plan(f"SELECT id FROM {TABLE} WHERE isinf(x)")

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

Make it faster

• Compare with the largest DOUBLE. x > 1.7976931348623157e308 compares the raw column with a constant, so it's pushed down to VAST DataBase and the plan has no FILTER step. It keeps inf, not -inf. NaN compares larger than every number in the Query Engine (see isnan), so it keeps NaN rows too: the second line shows rows 2 (inf) and 4 (NaN) for this table:

plan(f"SELECT id FROM {TABLE} WHERE x > 1.7976931348623157e308")
run(f"SELECT id FROM {TABLE} WHERE x > 1.7976931348623157e308 ORDER BY id LIMIT 10")

┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
[(2,), (4,)]

• Avoid writing infinities. If an infinite value means "no answer", store NULL instead: aggregates skip NULLs, while a sum of a column that holds both inf and -inf is NaN.

Limitations and errors

• A string literal must be cast. isinf('inf') fails with Could not choose a best candidate function for the function call "isinf(STRING_LITERAL)", because the literal could be a number, a date or a timestamp. Write isinf('inf'::DOUBLE).
• Numbers, dates and timestamps only. A BLOB, boolean, list or interval fails with No function matches the given name and argument types.
• Other names aren't available. is_infinite() and an infinity() constant don't exist (Scalar Function with name is_infinite does not exist!); use isinf() and 'inf'::DOUBLE:

run("SELECT is_infinite(1.0)")
run("SELECT infinity()")
run("SELECT 'inf'::DOUBLE, 'infinity'::DOUBLE, '-Infinity'::DOUBLE")

InternalError: Catalog Error: Scalar Function with name is_infinite does not exist!
InternalError: Catalog Error: Scalar Function with name infinity does not exist!
[(inf, inf, -inf)]

Similar functions

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: isnan, isinf and isfinite.
• isinf for dates and timestamps.
• Where filters run and pushdowns.
• EXPLAIN: how to read a plan.