Updating index schema

Updating index schema in RT mode

ALTER TABLE index {ADD|DROP} COLUMN column_name [{INTEGER|INT|BIGINT|FLOAT|BOOL|MULTI|MULTI64|JSON|STRING|TIMESTAMP}]

It supports adding one attribute at a time for both plain and RT indexes. The int, bigint, float, bool, multi-valued, multi-valued 64bit, json and string attribute types are supported. You can add json and string attributes, but you cannot modify their values.

Important notes:

  • Querying an index is impossible (because of a write lock) while adding a column.
  • Newly created attribute's values are set to 0.
  • ALTER will not work for distributed indexes and indexes without any attributes.
  • DROP COLUMN will fail if an index has only one attribute.

Updating index schema in plain mode

ALTER RTINDEX index RECONFIGURE

ALTER can also reconfigure an RT index in plain mode, so that new tokenization, morphology, and other text processing settings from the configuration file take effect on the newly INSERT-ed rows, while retaining the existing rows as they were. Internally, it forcibly saves the current RAM chunk as a new disk chunk, and adjusts the index header, so that the new rows are tokenized using the new rules.

Example
📋
mysql> desc plain;
+------------+-----------+
| Field      | Type      |
+------------+-----------+
| id         | bigint    |
| text       | field     |
| group_id   | uint      |
| date_added | timestamp |
+------------+-----------+
4 rows in set (0.01 sec)

mysql> alter table plain add column test integer;
Query OK, 0 rows affected (0.04 sec)

mysql> desc plain;
+------------+-----------+
| Field      | Type      |
+------------+-----------+
| id         | bigint    |
| text       | field     |
| group_id   | uint      |
| date_added | timestamp |
| test       | uint      |
+------------+-----------+
5 rows in set (0.00 sec)

mysql> alter table plain drop column group_id;
Query OK, 0 rows affected (0.01 sec)

mysql> desc plain;
+------------+-----------+
| Field      | Type      |
+------------+-----------+
| id         | bigint    |
| text       | field     |
| date_added | timestamp |
| test       | uint      |
+------------+-----------+
4 rows in set (0.00 sec)

Functions

Mathematical functions

ABS()

Returns the absolute value of the argument.

ATAN2()

Returns the arctangent function of two arguments, expressed in radians.

BITDOT()

BITDOT(mask, w0, w1, ...) returns the sum of products of an each bit of a mask multiplied with its weight. bit0*w0 + bit1*w1 + ...

CEIL()

Returns the smallest integer value greater or equal to the argument.

COS()

Returns the cosine of the argument.

CRC32()

Returns the CRC32 value of a string argument.

EXP()

Returns the exponent of the argument (e=2.718... to the power of the argument).

FIBONACCI()

Returns the N-th Fibonacci number, where N is the integer argument. That is, arguments of 0 and up will generate the values 0, 1, 1, 2, 3, 5, 8, 13 and so on. Note that the computations are done using 32-bit integer math and thus numbers 48th and up will be returned modulo 2\^32.

FLOOR()

Returns the largest integer value lesser or equal to the argument.

GREATEST()

GREATEST(attr_json.some_array) function takes JSON array as the argument, and returns the greatest value in that array. Also works for MVA.

IDIV()

Returns the result of an integer division of the first argument by the second argument. Both arguments must be of an integer type.

LEAST()

LEAST(attr_json.some_array) function takes JSON array as the argument, and returns the least value in that array. Also works for MVA.

LN()

Returns the natural logarithm of the argument (with the base of e=2.718...).

LOG10()

Returns the common logarithm of the argument (with the base of 10).

LOG2()

Returns the binary logarithm of the argument (with the base of 2).

MAX()

Returns the bigger of two arguments.

MIN()

Returns the smaller of two arguments.

POW()

Returns the first argument raised to the power of the second argument.

RAND()

RAND(seed) function returns a random float between 0..1. Optional, an integer seed value can be specified.

SIN()

Returns the sine of the argument.

SQRT()

Returns the square root of the argument.