| (bitwise OR)

Applies to VAST Cluster 5.5.

Functions › Operators and predicates › Bitwise operators. a | b returns an integer whose bits are set where they're set in a, in b, or in both. Use it to combine flags into a bit mask: 1 | 2 | 4 is 7.

Syntax

a | b

Returns: the integer type of the arguments: UTINYINT | UTINYINT is a UTINYINT.

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_operators_bitwise_or. 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 four users with a permission mask: 1 is read, 2 is write and 4 is admin. 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_operators_bitwise_or"'

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}.users"
run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}")
run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, name VARCHAR, perms INTEGER)")
run(f"INSERT INTO {TABLE} VALUES (1, 'ada', 7), (2, 'grace', 5), (3, 'alan', 1), (4, NULL, NULL)")

[]
[]
[(4,)]

What it does

| compares the two values bit by bit and sets a bit in the result where either has it set: 12 | 10 is 14, because 12 is 1100 in binary, 10 is 1010, and together they cover 1110. A bit that's already set stays set, so 7 | 2 is still 7. Negative numbers are in two's complement, so -1 has every bit set and 12 | -1 is -1.

On BIT values | works bit by bit as well; see Bitwise operators on BIT values.

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 12 | 10, 12 | -1, 0 | 0, 1 | 2 | 4")
run("SELECT NULL | NULL, 1 | NULL, NULL | 1")
run("SELECT (-128)::TINYINT | 1::TINYINT, typeof(12::UTINYINT | 10::UTINYINT)")
run(f"SELECT id, '12' | perms FROM {TABLE} ORDER BY id LIMIT 10")
run(f"SELECT 'abc' | perms FROM {TABLE} LIMIT 1")
run("SELECT 1.5 | 1")
run("SELECT true | false")

[(14, -1, 0, 7)]
[(None, None, None)]
[(-127, 'UTINYINT')]
[(1, 15), (2, 13), (3, 13), (4, None)]
OSError: Could not convert string 'abc' to INT32
InternalError: Binder Error: No function matches the given name and argument types '|(DECIMAL(2,1), INTEGER_LITERAL)'. You might need to add explicit type casts.
InternalError: Binder Error: No function matches the given name and argument types '|(BOOLEAN, BOOLEAN)'. You might need to add explicit type casts.

Examples

Give every user the write bit (2). Users who already have it keep the same mask:

run(f"SELECT id, name, perms, perms | 2 FROM {TABLE} ORDER BY id LIMIT 10")

[(1, 'ada', 7, 7), (2, 'grace', 5, 7), (3, 'alan', 1, 3), (4, None, None, None)]

Keep the users who would gain a permission from the write bit, that is, whose mask changes:

run(f"SELECT id, name FROM {TABLE} WHERE (perms | 2) <> perms ORDER BY id LIMIT 10")

[(2, 'grace'), (3, 'alan')]

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 an operation on a column, so | on a column is always computed by the Query Engine:

• In the SELECT list, the scan reads the column and the Query Engine computes | for each row it returns.
• In WHERE, the scan sends the column for every row, and a FILTER step in the Query Engine computes | 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 (perms | 2) <> perms")

┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│   ((perms | 2) != perms)  │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│           perms           │
│             id            │
│                           │
└───────────────────────────┘

Make it faster

• Build a mask from constants. | on constants is computed before the scan, so perms = (1 | 2 | 4) is a comparison of the raw column with a constant, which is pushed down to VAST DataBase. The plan has no FILTER step:

plan(f"SELECT id FROM {TABLE} WHERE perms = (1 | 2 | 4)")

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

• Store the flags you filter on often. Keep a flag in its own BOOLEAN column when you write the rows: a comparison of that column with a constant is pushed down, an operation on perms isn't.

Limitations and errors

• Integers and BIT only. A DECIMAL, DOUBLE, FLOAT, BOOLEAN, DATE, INTERVAL, BLOB or list fails with No function matches the given name and argument types, for example '|(DOUBLE, INTEGER)'. Cast the value to an integer type first.
• No logical OR. true | false fails; use OR for booleans.
• No bitor function. bitor(12, 10) fails with Scalar Function with name bitor does not exist!. Use |.
• A string must be a whole number. A string next to an integer is converted to that integer's type at run time; 'abc' | perms fails with Could not convert string 'abc' to INT32.
• BIT results come back as bytes. The driver returns a BIT value as bytes; see Bitwise operators on BIT values.

run("SELECT 1.5::DOUBLE | 1")
run("SELECT CAST(1.5::DOUBLE AS INTEGER) | 1, true OR false")
run("SELECT bitor(12, 10)")

InternalError: Binder Error: No function matches the given name and argument types '|(DOUBLE, INTEGER_LITERAL)'. You might need to add explicit type casts.
[(3, True)]
InternalError: Catalog Error: Scalar Function with name bitor does not exist!

Similar functions

run("SELECT 12 | 10, 12 & 10, xor(12, 10), ~12")

[(14, 8, 6, -13)]

Clean up:

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

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[]

See also

• Operators and predicates: all the operators.
• Bitwise operators on BIT values.
• Where filters run and pushdowns.
• EXPLAIN: how to read a plan.