On this page Carat arrow pointing down

The BYTES data type stores binary strings of variable length.


In CockroachDB, the following are aliases for BYTES:

  • BLOB


To express a byte array constant, see the section on byte array literals for more details. For example, the following three are equivalent literals for the same byte array: b'abc', b'\141\142\143', b'\x61\x62\x63'.

In addition to this syntax, CockroachDB also supports using string literals, including the syntax '...', e'...' and x'....' in contexts where a byte array is otherwise expected.


The size of a BYTES value is variable, but it's recommended to keep values under 1 MB to ensure adequate performance. Above that threshold, write amplification and other considerations may cause significant performance degradation.


We strongly recommend adding size limits to all indexed columns, which includes columns in primary keys.

Values exceeding 1 MiB can lead to storage layer write amplification and cause significant performance degradation or even crashes due to OOMs (out of memory errors).

To add a size limit using CREATE TABLE:

CREATE TABLE name (first STRING(100), last STRING(100));

To add a size limit using ALTER TABLE ... ALTER COLUMN:

SET enable_experimental_alter_column_type_general = true;


If your application requires large binary input in single queries, you can store the blobs somewhere your client can access them (using a cloud storage service, for example), and then reference their addresses from a statement.



> -- explicitly typed BYTES literals
> INSERT INTO bytes VALUES (1, b'\141\142\143'), (2, b'\x61\x62\x63'), (3, b'\141\x62\c');

> -- string literal implicitly typed as BYTES
> INSERT INTO bytes VALUES (4, 'abc');

> SELECT * FROM bytes;
| a |  b  |
| 1 | abc |
| 2 | abc |
| 3 | abc |
| 4 | abc |
(4 rows)

Supported conversions

BYTES values can be cast explicitly to STRING. This conversion always succeeds. Two conversion modes are supported, controlled by the session variable bytea_output:

  • hex (default): The output of the conversion starts with the two characters \, x and the rest of the string is composed by the hexadecimal encoding of each byte in the input. For example, x'48AA'::STRING produces '\x48AA'.

  • escape: The output of the conversion contains each byte in the input, as-is if it is an ASCII character, or encoded using the octal escape format \NNN otherwise. For example, x'48AA'::STRING produces '0\252'.

STRING values can be cast explicitly to BYTES. This conversion will fail if the hexadecimal digits are not valid, or if there is an odd number of them. Two conversion modes are supported:

  • If the string starts with the two special characters \ and x (e.g., \xAABB), the rest of the string is interpreted as a sequence of hexadecimal digits. The string is then converted to a byte array where each pair of hexadecimal digits is converted to one byte.

  • Otherwise, the string is converted to a byte array that contains its UTF-8 encoding.


While both STRING and BYTES can appear to have similar behavior in many situations, one should understand their nuance before casting one into the other.

STRING treats all of its data as characters, or more specifically, Unicode code points. BYTES treats all of its data as a byte string. This difference in implementation can lead to dramatically different behavior. For example, let's take a complex Unicode character such as ☃ (the snowman emoji):

> SELECT length('☃'::string);
> SELECT length('☃'::bytes);

In this case, LENGTH(string) measures the number of Unicode code points present in the string, whereas LENGTH(bytes) measures the number of bytes required to store that value. Each character (or Unicode code point) can be encoded using multiple bytes, hence the difference in output between the two.

Translating literals to STRING vs. BYTES

A literal entered through a SQL client will be translated into a different value based on the type:

  • BYTES give a special meaning to the pair \x at the beginning, and translates the rest by substituting pairs of hexadecimal digits to a single byte. For example, \xff is equivalent to a single byte with the value of 255. For more information, see SQL Constants: String literals with character escapes.
  • STRING does not give a special meaning to \x, so all characters are treated as distinct Unicode code points. For example, \xff is treated as a STRING with length 4 (\, x, f, and f).

See also

Data Types

Yes No
On this page

Yes No