hour

Applies to VAST Cluster 5.5.

Functions › Date and time functions › Parts of a date or time. Returns the hour of a timestamp or time of day, from 0 to 23, or the hours of an interval.

Syntax

hour(value)

Returns: BIGINT.

Same as: date_part('hour', value) and extract(hour FROM value); see date_part.

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_date_time_hour. 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 five events. Each has a date (d), a timestamp (ts), a time of day (t) and a timestamp with nanoseconds (tns). Row 4 has no values, and row 5 is the last moment of 1969:

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_date_time_hour"'

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, d DATE, ts TIMESTAMP, t TIME, tns TIMESTAMP_NS)")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, DATE '2026-02-28', TIMESTAMP '2026-02-28 23:15:00', TIME '23:15:00', "
    "CAST('2026-02-28 23:15:00.123456789' AS TIMESTAMP_NS)), "
    "(2, DATE '2026-03-01', TIMESTAMP '2026-03-01 08:30:45.123456', TIME '08:30:45.123456', "
    "CAST('2026-03-01 08:30:45.123456' AS TIMESTAMP_NS)), "
    "(3, DATE '2024-12-30', TIMESTAMP '2024-12-30 12:00:00', TIME '12:00:00', "
    "CAST('2024-12-30 12:00:00' AS TIMESTAMP_NS)), "
    "(4, NULL, NULL, NULL, NULL), "
    "(5, DATE '1969-12-31', TIMESTAMP '1969-12-31 23:59:59.999999', TIME '23:59:59.999999', "
    "CAST('1969-12-31 23:59:59.999999999' AS TIMESTAMP_NS))")

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[(5,)]

What it does

hour returns the hour of a timestamp or time of day on the 24-hour clock: hour(TIMESTAMP '2024-02-29 13:45:30') and hour(TIME '13:45:30') are both 13. It works on every timestamp precision (TIMESTAMP, TIMESTAMP_NS, TIMESTAMP_MS, TIMESTAMP_S). A DATE has no time, so its hour is always 0.

On an INTERVAL, hour returns the whole hours in its time part. It doesn't count days or months, and it doesn't wrap at 24:

To split 36 hours into 1 day and 12 hours first, use normalized_interval: hour(normalized_interval(INTERVAL '36 hours')) is 12. For the total length of an interval in hours, use epoch(...) / 3600.

NULLs and edge cases

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

run(f"SELECT id, hour(ts), hour(t) FROM {TABLE} WHERE id = 4")
run("SELECT hour(DATE 'infinity'), hour(TIMESTAMP '-infinity'), hour(DATE '2026-03-01'), hour(TIME '23:59:59.999999'), "
    "hour(TIME '24:00:00'), hour(TIMETZ '13:45:30.123456+02:30')")
run("SELECT hour(INTERVAL '1 year 2 months 3 days 04:05:06.789'), hour(INTERVAL '36 hours'), "
    "hour(INTERVAL '25 months 40 days 30 hours'), hour(INTERVAL '-90 minutes')")
run("SELECT hour(NULL)")
run("SELECT hour('13:45:30')")
run("SELECT hour(123)")

[(4, None, None)]
[(None, None, 0, 23, 24, 13)]
[(4, 36, 30, -1)]
InternalError: Binder Error: Could not choose a best candidate function for the function call "hour("NULL")". In order to select one, please add explicit type casts.
InternalError: Binder Error: Could not choose a best candidate function for the function call "hour(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'hour(INTEGER_LITERAL)'. You might need to add explicit type casts.

Examples

The hour of each event's timestamp and time of day, and of its date:

run(f"SELECT id, hour(ts), hour(t), hour(d) FROM {TABLE} ORDER BY id LIMIT 10")

[(1, 23, 23, 0), (2, 8, 8, 0), (3, 12, 12, 0), (4, None, None, None), (5, 23, 23, 0)]

Keep only the events from noon onwards, by their time of day:

run(f"SELECT id FROM {TABLE} WHERE hour(t) >= 12 ORDER BY id LIMIT 10")

[(1,), (3,), (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 hour() is always computed by the Query Engine:

• In the SELECT list, the scan reads the column and the Query Engine computes hour() for each row it returns.
• In WHERE, the scan sends the column for every row, and a FILTER step in the Query Engine computes hour() 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 hour(t) >= 12")

┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│     ("hour"(t) >= 12)     │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             t             │
│             id            │
│                           │
└───────────────────────────┘

Make it faster

• On a TIME column, compare the column itself. t >= TIME '12:00:00' returns the same rows as hour(t) >= 12, and it's pushed down to VAST DataBase, so rows that don't match never leave storage. BETWEEN works too, for a window such as t BETWEEN TIME '08:00:00' AND TIME '12:00:00'. The plan has no FILTER step:

plan(f"SELECT id FROM {TABLE} WHERE t >= TIME '12:00:00'")

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

• For one hour of one day, filter on a range of the raw timestamp: ts >= TIMESTAMP '2026-03-01 08:00:00' AND ts < TIMESTAMP '2026-03-01 09:00:00'.
• Store the time of day, or the hour, if you filter on it across days. hour(ts) >= 12 for every day has no single range on ts. Keep the time of day in its own TIME column, as t is here, or the hour in a number column, and compare that column with a constant.

Limitations and errors

• No time-zone support. On a TIMESTAMP WITH TIME ZONE value, such as now(), hour fails with an Extension Autoloading Error. Cast the value to TIMESTAMP first; see time zones.
• TIMESTAMP_NS just before 1970. Row 5's tns, 1969-12-31 23:59:59.999999999, gives 0, not 23. Store such values as TIMESTAMP if you need their hour.
• One argument. hour(ts, ts) fails with No function matches the given name and argument types 'hour(TIMESTAMP, TIMESTAMP)'.

run(f"SELECT id, hour(tns), hour(ts) FROM {TABLE} ORDER BY id LIMIT 10")
run(f"SELECT hour(ts, ts) FROM {TABLE} LIMIT 1")

[(1, 23, 23), (2, 8, 8), (3, 12, 12), (4, None, None), (5, 0, 23)]
InternalError: Binder Error: No function matches the given name and argument types 'hour(TIMESTAMP, TIMESTAMP)'. You might need to add explicit type casts.

Similar functions

On INTERVAL '36 hours': hour gives 36, epoch(...) / 3600 gives 36.0, day gives 0, and hour(normalized_interval(...)) gives 12.

run("SELECT hour(TIMESTAMP '2024-02-29 13:45:30.123456'), minute(TIMESTAMP '2024-02-29 13:45:30.123456'), "
    "date_trunc('hour', TIMESTAMP '2024-02-29 13:45:30.123456'), strftime(TIMESTAMP '2024-02-29 13:45:30.123456', '%H')")
run("SELECT hour(INTERVAL '36 hours'), epoch(INTERVAL '36 hours') / 3600, day(INTERVAL '36 hours'), "
    "hour(normalized_interval(INTERVAL '36 hours'))")

[(13, 45, datetime.datetime(2024, 2, 29, 13, 0), '13')]
[(36, 36.0, 0, 12)]

Clean up:

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

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See also

• date_part: any part of a value, by name.
• Date and time functions: all the date and time functions.
• Where filters run and pushdowns.
• EXPLAIN: how to read a plan.