DECIMAL

Description

DECIMAL(P[,S])

High-precision fixed-point value. P stands for the total number of significant numbers (precision). S stands for the maximum number of decimal points (scale).

If P is omitted, the default is 10. If S is omitted, the default is 0.

• Decimal V2

  The range of P is [1,27] and the range of S is [0,9]. P must be greater than or equal to the value of S. The default value of S is 0.

• Fast Decimal (Decimal V3)

  The range of P is [1,38] and the range of S is [0, P]. The default value of S is 0. Fast Decimal provides a higher precision.

  Major optimizations:

  ​1. Fast Decimal uses variable-width integers to express decimals. For example, it uses 64-bit integers to express decimals whose precision is less than or equal to 18. Whereas, Decimal V2 uses 128-bit integers uniformly for all decimals. Arithmetic operations and conversion operations on 64-bit processors use fewer instructions, which greatly improves performance.

  ​2. Compared with Decimal V2, Fast Decimal made significant optimizations in some algorithms, especially in multiplication, which improves performance by about 4 times.

Fast Decimal is controlled by the FE dynamic parameter enable_decimal_v3, which is true by default.

From v3.1 onwards, StarRocks supports Fast Decimal entries in ARRAY, MAP, and STRUCT.

Limits

StarRocks does not support querying DECIMAL data in ORC and Parquet files from Hive.

Examples

Define DECIMAL columns when creating a table.

CREATE TABLE decimalDemo (
    pk BIGINT(20) NOT NULL COMMENT "",
    account DECIMAL(20,10) COMMENT ""
) ENGINE=OLAP 
DUPLICATE KEY(pk)
COMMENT "OLAP"
DISTRIBUTED BY HASH(pk);

INSERT INTO decimalDemo VALUES
(1,3.141592656),
(2,21.638378),
(3,4873.6293048479);

SELECT * FROM decimalDemo;
+------+-----------------+
| pk   | account         |
+------+-----------------+
|    1 |    3.1415926560 |
|    3 | 4873.6293048479 |
|    2 |   21.6383780000 |
+------+-----------------+

keywords

decimal, decimalv2, decimalv3, fast decimal