yearweek

Applies to VAST Cluster 5.5.

Functions › Date and time functions › Weeks and days of the week. Returns the ISO 8601 year and week of a date or timestamp as one number: the year times 100 plus the week, such as 202609 for week 9 of 2026.

Syntax

yearweek(value)

Returns: BIGINT.

Same as: date_part('yearweek', 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_yearweek. 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 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, row 6 is the last moment of 1969, and row 7 is a Sunday early in January 2027:

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_yearweek"'

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 '2024-02-29', TIMESTAMP '2024-02-29 00:00:00', TIME '00:00:00', "
    "CAST('2024-02-29 00:00:00' AS TIMESTAMP_NS)), "
    "(6, 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)), "
    "(7, DATE '2027-01-03', TIMESTAMP '2027-01-03 00:00:00.5', TIME '00:00:00.000001', "
    "CAST('2027-01-03 00:00:00.5' AS TIMESTAMP_NS))")

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[(7,)]

What it does

yearweek combines isoyear and week: isoyear(value) * 100 + week(value). ISO 8601 weeks start on Monday, and week 1 of a year is the week that holds the year's first Thursday. So the first days of January can belong to the last week of the year before, and the last days of December to week 1 of the next year:

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, yearweek(ts) FROM {TABLE} WHERE id = 4")
run("SELECT yearweek(DATE '2026-01-01'), yearweek(DATE '2024-12-30'), yearweek(DATE '2021-01-01'), "
    "yearweek(DATE '2027-01-03')")
run("SELECT yearweek(DATE 'infinity'), yearweek(TIMESTAMP '-infinity'), yearweek(DATE '0001-01-01'), "
    "yearweek(DATE '9999-12-31'), yearweek(CAST('0044-03-15 (BC)' AS DATE)), "
    "yearweek(TIMESTAMP '1969-12-31 23:59:59.999999')")
run("SELECT yearweek(NULL)")
run("SELECT yearweek(INTERVAL '1 year 2 months 3 days')")
run("SELECT yearweek(TIME '13:45:30')")
run("SELECT yearweek('2026-03-01')")
run("SELECT yearweek(123)")

[(4, None)]
[(202601, 202501, 202053, 202653)]
[(None, None, 101, 999952, -4311, 197001)]
InternalError: Binder Error: Could not choose a best candidate function for the function call "yearweek("NULL")". In order to select one, please add explicit type casts.
OSError: interval units "week" not recognized
InternalError: Binder Error: No function matches the given name and argument types 'yearweek(TIME)'. You might need to add explicit type casts.
InternalError: Binder Error: Could not choose a best candidate function for the function call "yearweek(STRING_LITERAL)". In order to select one, please add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types 'yearweek(INTEGER_LITERAL)'. You might need to add explicit type casts.

Examples

The ISO year and week of each event. Row 3 (30 December 2024) is in week 1 of 2025, and row 6 (31 December 1969) in week 1 of 1970:

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

[(1, datetime.date(2026, 2, 28), 202609, 202609), (2, datetime.date(2026, 3, 1), 202609, 202609), (3, datetime.date(2024, 12, 30), 202501, 202501), (4, None, None, None), (5, datetime.date(2024, 2, 29), 202409, 202409), (6, datetime.date(1969, 12, 31), 197001, 197001), (7, datetime.date(2027, 1, 3), 202653, 202653)]

The same week as a label in the ISO format, such as 2026-W09, with the %G (ISO year) and %V (ISO week) codes of strftime:

run(f"SELECT id, strftime(d, '%G-W%V') FROM {TABLE} ORDER BY id LIMIT 10")

[(1, '2026-W09'), (2, '2026-W09'), (3, '2025-W01'), (4, None), (5, '2024-W09'), (6, '1970-W01'), (7, '2026-W53')]

Keep only the events in week 9 of 2026:

run(f"SELECT id FROM {TABLE} WHERE yearweek(d) = 202609 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 yearweek() is always computed by the Query Engine:

• In the SELECT list, the scan reads the column and the Query Engine computes yearweek() for each row it returns.
• In WHERE, the scan sends the column for every row, and a FILTER step in the Query Engine computes yearweek() 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 yearweek(d) = 202609")

┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│   (yearweek(d) = 202609)  │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│             d             │
│             id            │
│                           │
└───────────────────────────┘

Make it faster

• For one week, filter on a range of the raw column. Week 9 of 2026 runs from Monday 23 February to Sunday 1 March, so d >= DATE '2026-02-23' AND d < DATE '2026-03-02' selects the same rows. The range is pushed down to VAST DataBase, so rows outside it never leave storage. The plan for the range has no FILTER step:

plan(f"SELECT id FROM {TABLE} WHERE d >= DATE '2026-02-23' AND d < DATE '2026-03-02'")

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

• Find the week's Monday with date_trunc. date_trunc('week', d) returns the Monday that starts the ISO week, which gives you the start of the range; see date_trunc.
• Store the week if you filter on many weeks. Compute yearweek when you write the rows and keep it in its own column: event_week = 202609 is pushed down, yearweek(d) = 202609 isn't.

Limitations and errors

• ISO weeks only. yearweek always uses ISO 8601 weeks, which start on Monday. For weeks that start on Sunday, use the %U code of strftime.
• No time-zone support. On a TIMESTAMP WITH TIME ZONE value, such as now(), yearweek fails with an Extension Autoloading Error. Cast the value to TIMESTAMP first; see time zones.
• Not for TIME or INTERVAL. The error for an INTERVAL lists yearweek(INTERVAL) among the candidates, but running it fails with interval units "week" not recognized.

Similar functions

run("SELECT yearweek(DATE '2024-12-30'), week(DATE '2024-12-30'), isoyear(DATE '2024-12-30'), "
    "year(DATE '2024-12-30'), strftime(DATE '2024-12-30', '%G%V'), date_part('yearweek', DATE '2024-12-30')")

[(202501, 1, 2025, 2024, '202501', 202501)]

Clean up:

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

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See also

• week and isoyear: the two halves of yearweek.
• Date and time functions: all the date and time functions.
• Where filters run and pushdowns.
• EXPLAIN: how to read a plan.