index on decimal column EXPLAIN bug when encoding decimal

indexDecimalBug.md

Summary

When creating an index on a column with type DECIMAL, EXPLAIN SELECT shows the indexed range it's retrieving as:

EXPLAIN SELECT decimalCol FROM t WHERE decimalCol>10;
+-------+------+------------------------------------------------------------------------------------------------+
| Level | Type |                                          Description                                           |
+-------+------+------------------------------------------------------------------------------------------------+
|     0 | scan | t@decimalIndex /<util/encoding/decimal.go:395: did not find terminator 0x0 in buffer 0x1401>-  |
+-------+------+------------------------------------------------------------------------------------------------+

However, the SELECT statement still executes, so it looks like it's just a bug with encoding the DECIMAL value in EXPLAIN's output.

INSERT INTO t VALUES (11.1);
SELECT decimalCol FROM t WHERE decimalCol>10;
+------------+
| decimalCol |
+------------+
|       11.1 |
+------------+

NOTE: Tested indexes created with INT, FLOAT, BOOL, DATE, TIMESTAMP, INTERVAL, STRING, and BYTE columns and there were no issues.

Steps to repro

Create table

CREATE TABLE t (decimalCol DECIMAL);

Create index on the DECIMAL column

CREATE INDEX decimalIndex ON t (decimalCol);

EXPLAIN SELECT demos bug

EXPLAIN SELECT decimalCol FROM t WHERE decimalCol>10;

+-------+------+------------------------------------------------------------------------------------------------+
| Level | Type |                                          Description                                           |
+-------+------+------------------------------------------------------------------------------------------------+
|     0 | scan | t@decimalIndex /<util/encoding/decimal.go:395: did not find terminator 0x0 in buffer 0x1401>-  |
+-------+------+------------------------------------------------------------------------------------------------+

Other tested table configurations

All of the following tables generate the same error

• Column with precision and scale specified

CREATE TABLE t (decimalCol DECIMAL(9,2));

• Table with primary key

CREATE TABLE t (id INT PRIMARY KEY, decimalCol DECIMAL);

• Table with primary key; column with precision and scale identified

CREATE TABLE t (id INT PRIMARY KEY, decimalCol DECIMAL);