epoch

Applies to VAST Cluster 5.5.

Functions › Date and time functions › Epoch values. Returns the number of seconds since 1970-01-01 00:00:00 of a date or timestamp, with the fraction, as a DOUBLE. On a time of day it returns the seconds since midnight, and on an interval its length in seconds.

Syntax

epoch(value)

Returns: DOUBLE.

Same as: date_part('epoch', value) and extract(epoch 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_epoch. 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_epoch"'

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

epoch converts a value to seconds, as a DOUBLE with the fraction of a second:

Values before 1970 are negative: one microsecond before 1970 (row 5) is -1e-06.

On an INTERVAL, epoch counts a month as 30 days and a year as 365.25 days: epoch(INTERVAL '1 month') is 2592000.0, and epoch(INTERVAL '1 year') is 31557600.0. epoch_ms, epoch_us and epoch_ns count a year as 12 months of 30 days instead.

On a TIME WITH TIME ZONE, the result is the seconds since midnight of the local time; the offset isn't applied: epoch(TIMETZ '13:45:30.123456+02:30') is 49530.123456.

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, epoch(ts) FROM {TABLE} WHERE id = 4")
run("SELECT epoch(DATE 'infinity'), epoch(TIMESTAMP '-infinity'), epoch(DATE '0001-01-01'), "
    "epoch(TIMESTAMP '1969-12-31 23:59:59.5'), epoch(TIME '24:00:00')")
run("SELECT epoch(INTERVAL '1 year 2 months 3 days 04:05:06.789'), "
    "epoch(INTERVAL '-1 year -2 months -3 days -04:05:06.789'), epoch(TIMESTAMP_NS '2024-02-29 13:45:30.123456789')")
run("SELECT epoch(NULL)")
run("SELECT epoch('2024-02-29 13:45:30')")
run("SELECT epoch(123)")

[(4, None)]
[(None, None, -62135596800.0, -0.5, 86400.0)]
[(37015506.789, -37015506.789, 1709214330.123456)]
InternalError: Binder Error: Could not choose a best candidate function for the function call "epoch("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 "epoch(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'epoch(INTEGER_LITERAL)'. You might need to add explicit type casts.

Examples

The seconds since 1970 of each event's date and timestamp, and the seconds since midnight of its time:

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

[(1, 1772236800.0, 1772320500.0, 83700.0), (2, 1772323200.0, 1772353845.123456, 30645.123456), (3, 1735516800.0, 1735560000.0, 43200.0), (4, None, None, None), (5, -86400.0, -1e-06, 86399.999999)]

The length of an interval in seconds, and the seconds between two timestamps:

run("SELECT epoch(INTERVAL '1 month'), epoch(INTERVAL '1 year'), "
    "epoch(TIMESTAMP '2026-03-01 09:01:00') - epoch(TIMESTAMP '2026-03-01 08:59:00')")

[(2592000.0, 31557600.0, 120.0)]

Keep only the events after a Unix time in seconds. This works, but Make it faster has a faster way to write it:

run(f"SELECT id FROM {TABLE} WHERE epoch(ts) > 1772300000 ORDER BY id LIMIT 10")

[(1,), (2,)]

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 epoch() is always computed by the Query Engine:

• In the SELECT list, the scan reads the column and the Query Engine computes epoch() for each row it returns.
• In WHERE, the scan sends the column for every row, and a FILTER step in the Query Engine computes epoch() 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 epoch(ts) > 1772300000")

┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│ (epoch(ts) > 1772300000.0)│
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             ts            │
│             id            │
│                           │
└───────────────────────────┘

Make it faster

• Convert the number to a timestamp, not the column to a number. ts > make_timestamp(1772300000000000) (microseconds) and ts > CAST(to_timestamp(1772300000) AS TIMESTAMP) (seconds) return the same rows as epoch(ts) > 1772300000. The function is applied to a constant, so the comparison of the raw column is pushed down to VAST DataBase, and the plans have no FILTER step:

plan(f"SELECT id FROM {TABLE} WHERE ts > make_timestamp(1772300000000000)")
plan(f"SELECT id FROM {TABLE} WHERE ts > CAST(to_timestamp(1772300000) AS TIMESTAMP)")
run(f"SELECT id FROM {TABLE} WHERE ts > make_timestamp(1772300000000000) ORDER BY id LIMIT 10")

┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
┌───────────────────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│      Projections: id      │
│                           │
└───────────────────────────┘
[(1,), (2,)]

• Use epoch() in the SELECT list, where it doesn't stop a filter from being pushed down.

Limitations and errors

• No time-zone support. On a TIMESTAMP WITH TIME ZONE value, such as now(), epoch fails with an Extension Autoloading Error. Cast the value to TIMESTAMP first, or use epoch_ms, which takes a TIMESTAMP WITH TIME ZONE. See time zones.
• Microseconds at most. On a TIMESTAMP_NS, the result has microsecond precision: row 5's 1969-12-31 23:59:59.999999999 gives 0.0, while epoch_ns gives -1. Use epoch_ns for nanoseconds.
• No reverse form. epoch(1772353845) fails with No function matches the given name and argument types 'epoch(INTEGER_LITERAL)'. To turn seconds into a timestamp, use to_timestamp. epoch_s and epoch_seconds don't exist.
• One argument. epoch(ts, ts) fails with No function matches the given name and argument types 'epoch(TIMESTAMP, TIMESTAMP)'.

run(f"SELECT id, epoch(tns), epoch_ns(tns) FROM {TABLE} ORDER BY id LIMIT 10")
run("SELECT epoch(1772353845)")
run("SELECT CAST(to_timestamp(1772353845) AS TIMESTAMP)")
run(f"SELECT epoch(ts, ts) FROM {TABLE} LIMIT 1")

[(1, 1772320500.123456, 1772320500123456789), (2, 1772353845.123456, 1772353845123456000), (3, 1735560000.0, 1735560000000000000), (4, None, None), (5, 0.0, -1)]
InternalError: Binder Error: No function matches the given name and argument types 'epoch(INTEGER_LITERAL)'. You might need to add explicit type casts.
[(datetime.datetime(2026, 3, 1, 8, 30, 45),)]
InternalError: Binder Error: No function matches the given name and argument types 'epoch(TIMESTAMP, TIMESTAMP)'. You might need to add explicit type casts.

Similar functions

run("SELECT epoch(TIMESTAMP '2024-02-29 13:45:30.123456'), date_part('epoch', TIMESTAMP '2024-02-29 13:45:30.123456'), "
    "epoch_ms(TIMESTAMP '2024-02-29 13:45:30.123456'), epoch_us(TIMESTAMP '2024-02-29 13:45:30.123456'), "
    "epoch_ns(TIMESTAMP '2024-02-29 13:45:30.123456'), julian(TIMESTAMP '2024-02-29 13:45:30.123456')")
run("SELECT epoch(INTERVAL '1 year 1 month 1 day'), date_part('epoch', INTERVAL '1 year 1 month 1 day'), "
    "epoch_ms(INTERVAL '1 year 1 month 1 day'), epoch_us(INTERVAL '1 year 1 month 1 day')")

[(1709214330.123456, 1709214330.123456, 1709214330123, 1709214330123456, 1709214330123456000, 2460370.573265318)]
[(34236000.0, 34236000.0, 33782400000, 33782400000000)]

Clean up:

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

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See also

• epoch_ms, epoch_us and epoch_ns: whole milliseconds, microseconds and nanoseconds.
• to_timestamp and make_timestamp: from a number back to a timestamp.
• Date and time functions: all the date and time functions.
• Where filters run and pushdowns.
• EXPLAIN: how to read a plan.