fdiv

Applies to VAST Cluster 5.5.

Functions › Numeric and math functions › Arithmetic. Divides a by b and rounds the quotient down (towards minus infinity) to a whole number, returned as a DOUBLE: fdiv(-5.5, 2) is -3.0. It goes with fmod: for ordinary values, a = fdiv(a, b) * b + fmod(a, b).

Syntax

fdiv(a, b)

Returns: DOUBLE, for every numeric input type.

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_fdiv. 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 six events with an offset in seconds from a reference time; negative offsets are before it. 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_numeric_fdiv"'

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}.events"
run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}")
run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, offset_s BIGINT)")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, 0), "
    "(2, 59), "
    "(3, 60), "
    "(4, 125), "
    "(5, -1), "
    "(6, NULL)")

[]
[]
[(6,)]

What it does

fdiv(a, b) is floor(a / b): the quotient, rounded down to a whole number. For a negative quotient, rounding down moves away from zero:

This differs from integer division with //, which truncates towards zero: -7 // 2 is -3, while fdiv(-7, 2) is -4.0. Use fdiv to put values into buckets of equal width, such as seconds into minutes, when some values are negative: fdiv(-1, 60) is -1.0, the minute before the reference time.

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 fdiv(NULL, 2), fdiv(1, NULL), fdiv(5, 0), fdiv(5.0, 0.0), fdiv(0, 0)")
run("SELECT fdiv('inf'::DOUBLE, 1), fdiv(1, 'inf'::DOUBLE), fdiv('NaN'::DOUBLE, 1), fdiv(1e308, 1e-308)")
run("SELECT fdiv(7::DECIMAL(4,1), 2), fdiv(9223372036854775807, 2), typeof(fdiv(5, 2))")
run("SELECT fdiv('7', 2)")

[(None, None, inf, inf, nan)]
[(inf, 0.0, nan, inf)]
[(3.0, 4.611686018427388e+18, 'DOUBLE')]
InternalError: Binder Error: No function matches the given name and argument types 'floor(INTERVAL)'. You might need to add explicit type casts.

Examples

The minute each event falls in, and the second within that minute from fmod. Compare with //, which puts the event at -1 seconds into minute 0:

run(f"SELECT id, offset_s, fdiv(offset_s, 60), fmod(offset_s, 60), offset_s // 60 FROM {TABLE} ORDER BY id LIMIT 10")

[(1, 0, 0.0, 0.0, 0), (2, 59, 0.0, 59.0, 0), (3, 60, 1.0, 0.0, 1), (4, 125, 2.0, 5.0, 2), (5, -1, -1.0, 59.0, 0), (6, None, None, None, None)]

The events in the first minute:

run(f"SELECT id, offset_s FROM {TABLE} WHERE fdiv(offset_s, 60) = 0 ORDER BY id LIMIT 10")

[(1, 0), (2, 59)]

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 fdiv() is always computed by the Query Engine:

• In the SELECT list, the scan reads the columns and the Query Engine computes fdiv() for each row it returns.
• In WHERE, the scan sends the columns for every row, and a FILTER step in the Query Engine computes fdiv() 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 fdiv(offset_s, 60) = 0")

┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│  (floor((CAST(offset_s AS │
│   DOUBLE) / 60.0)) = 0.0) │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│          offset_s         │
│             id            │
│                           │
└───────────────────────────┘

Make it faster

• Filter on a range of the raw column instead. fdiv(offset_s, 60) = 0 keeps the offsets from 0 to 59; offset_s >= 0 AND offset_s < 60 returns the same rows, and a comparison of the raw column with a constant is pushed down to VAST DataBase, so rows that don't match never leave storage. Its plan has no FILTER step:

plan(f"SELECT id FROM {TABLE} WHERE offset_s >= 0 AND offset_s < 60")

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

• Compute the bucket in the SELECT list of the rows you return, and filter on the raw column.

Limitations and errors

• The result is always a DOUBLE, also for integers: fdiv(7, 2) is 3.0. Cast it if you need an integer: CAST(fdiv(7, 2) AS BIGINT). Integers beyond about 16 significant digits lose precision in the DOUBLE.
• Division by zero returns inf, -inf or nan, not an error and not NULL. Test for it with isinf() and isnan(), or guard the divisor: fdiv(a, NULLIF(b, 0)) returns NULL instead.
• Numbers only. A date, boolean, list or BLOB fails with an error that names the division fdiv performs, for example No function matches the given name and argument types '/(DATE, INTEGER_LITERAL)'. A string, even a numeric one, fails with 'floor(INTERVAL)'. Cast strings to a number first.

run("SELECT CAST(fdiv(7, 2) AS BIGINT), isinf(fdiv(1, 0)), fdiv(1, NULLIF(0, 0))")
run("SELECT fdiv(DATE '2026-10-16', 2)")
run("SELECT fdiv(CAST('7' AS DOUBLE), 2)")

[(3, True, None)]
InternalError: Binder Error: No function matches the given name and argument types '/(DATE, INTEGER_LITERAL)'. You might need to add explicit type casts.
[(3.0,)]

Similar functions

run("SELECT fdiv(-7, 2), -7 // 2, floor(-7 / 2), fmod(-7, 2), divide(-7, 2)")
run("SELECT fdiv(7, 2), 7 // 2, floor(7 / 2), fmod(7, 2), divide(7, 2)")

[(-4.0, -3, -4.0, 1.0, -3)]
[(3.0, 3, 3.0, 1.0, 3)]

Clean up:

run(f"DROP TABLE IF EXISTS {TABLE}")
run(f"DROP SCHEMA IF EXISTS {SCHEMA}")
conn.close()

[]
[]

See also

• Numeric and math functions: all the numeric functions.
• fmod, // (integer division) and floor.
• Where filters run and pushdowns.
• EXPLAIN: how to read a plan.