Datatypes and Fixed Encoding

This topic describes standard datatypes and space-saving variations for values stored in OmniSci.

Datatypes

Each OmniSci datatype uses space in memory and on disk. Datatypes and sizes are listed in the following table.

Datatype Size (bytes) Notes
TEXT ENCODING DICT 4 Max cardinality 1 billion distinct string values.
TEXT ENCODING NONE Variable Size of the string + 6 bytes.
TIMESTAMP 8 Linux timestamp from 30610224000000 (1/1/1000 00:00:00.000) through 29379542399999 (12/31/2900 23:59:59.999). Can also be inserted and stored in human-readable format (YYYY-MM-DD HH:MM:SS).
TIME 8 Minimum value: 00:00:00; maximum value: 23:59:59.
DATE* 4 Minimum value: -2,147,483,648; maximum value: 2,147,483,647
Range in years: +/-588,350 around epoch
FLOAT 4 Variable precision. Minimum value: -3.4 x e^38; maximum value: 3.4 x e^38.
DOUBLE 8 Variable precision. Minimum value: -1.79 x e^308; maximum value: 1.79 x e^308
INTEGER 4 Minimum value: -2,147,483,647; maximum value: 2,147,483,647.
TINYINT 1 Minimum value: -127; maximum value: 127.
SMALLINT 2 Minimum value: -32,767; maximum value: 32,767.
BIGINT 8 Minimum value: -9,223,372,036,854,775,807; maximum value: 9,223,372,036,854,775,807.
BOOLEAN 1 TRUE: 'true', '1', 't'. FALSE: 'false', '0', 'f'. Text values are not case-sensitive.
DECIMAL/NUMERIC 8 Precise. Maximum precision: 19. Scale must be less than precision.

* In OmniSci release 4.4.0 and higher, you can use existing 8-byte DATE columns, but you can create only 4-byte DATE columns (default) and 2-byte DATE columns (see DATE ENCODING FIXED(16)).

Note
  • OmniSci does not support geometry arrays.
  • Timestamp values are always stored in 8 bytes. The greater the precision, the lower the fidelity.

Fixed Encoding

For certain datatypes, you can use a more compact representation of these values. The options for these datatypes are listed in the following table.

Encoding Size (bytes) Notes
TIMESTAMP ENCODING FIXED(32) 4 Range: 1901-12-13 20:45:53 - 2038-01-19 03:14:07
TIME ENCODING FIXED(32) 4 Range: 00:00:00 - 23:59:59
DATE ENCODING FIXED(32) 4 Default encoding, equivalent to DATE.
Range in years: +/-588,350 around epoch
DATE ENCODING FIXED(16) 2 Range: -32,768 - 32,767
Range in years: +/-90 around epoch.
TEXT ENCODING DICT(16) 2 Max cardinality 64K distinct string values
TEXT ENCODING DICT(8) 1 Max cardinality 255 distinct string values
INTEGER ENCODING FIXED(16) 2 Same as SMALLINT
INTEGER ENCODING FIXED(8) 1 Range: -127 - 127
SMALLINT ENCODING FIXED(8) 1 Range: -127 - 127
BIGINT ENCODING FIXED(32) 4 Same as INTEGER
BIGINT ENCODING FIXED(16) 2 Same as SMALLINT
BIGINT ENCODING FIXED(8) 1 Range: -127 - 127

To use these fixed length fields, the range or of the data must fit into the constraints as described.

These encodings are most effective on low-cardinality TEXT fields, where you can achieve large savings of storage space and improved processing speed, and on TIMESTAMP fields where the timestamps range between 1901-12-13 20:45:53 and 2038-01-19 03:14:07.

All encoding options are shown. Some of the INTEGER options overlap. For example, INTEGER ENCODINGFIXED(8) and SMALLINT ENCODINGFIXED(8) are essentially the same.

If a TEXT ENCODING field does not match the defined cardinality, OmniSci substitutes a NULL value and logs the change.

Understanding your schema and the scope of potential values in each field helps you achieve significant savings by carefully applying these fixed encoding types.

Defining Array Datatypes

Define datatype arrays by appending square brackets, as shown in the arrayexamples DDL sample.

CREATE TABLE arrayexamples (
tiny_int_array TINYINT[],
int_array INTEGER[],
big_int_array BIGINT[],
text_array TEXT[] ENCODING DICT(32), --OmniSci supports only DICT(32) TEXT arrays.
float_array FLOAT[],
double_array DOUBLE[],
decimal_array DECIMAL(18,6)[],
boolean_array BOOLEAN[],
date_array DATE[],
time_array TIME[],
timestamp_array TIMESTAMP[])

Geospatial Primitives

Geospatial Primitive Types
Type Description Example
POINT A point described by two coordinates. When the coordinates are longitude and latitude, OmniSci stores longitude first, and then latitude. POINT(0 0)
LINESTRING A sequence of 2 or more points and the lines that connect them. LINESTRING(0 0,1 1,1 2)
POLYGON A set of one or more rings (closed line strings), with the first representing the shape (external ring) and the rest representing holes in that shape (internal rings). POLYGON((0 0,4 0,4 4,0 4,0 0),(1 1, 2 1, 2 2, 1 2,1 1))
MULTIPOLYGON A set of one or more polygons. MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0),(1 1,2 1,2 2,1 2,1 1)), ((-1 -1,-1 -2,-2 -2,-2 -1,-1 -1)))

See Using Geospatial Objects.

Shared Dictionaries

You can improve performance of string operations and optimize storage using shared dictionaries. You can share dictionaries within a table or between different tables in the same database. The table with which you want to share dictionaries must exist when you create the table that references the TEXT ENCODING DICT field, and the column that you are referencing in that table must also exist. The following small DDL shows the basic structure:

CREATE TABLE text_shard (
i TEXT ENCODING DICT(32),
s TEXT ENCODING DICT(32),
SHARD KEY (i))
WITH (SHARD_COUNT = 2);

CREATE TABLE text_shard1 (
i TEXT,
s TEXT ENCODING DICT(32),
SHARD KEY (i),
SHARED DICTIONARY (i) REFERENCES text_shard(i))
WITH (SHARD_COUNT = 2);

In the table definition, make sure that referenced columns appear before the referencing columns.

For example, this DDL is a portion of the schema for the flights database. Because airports are both origin and destination locations, it makes sense to reuse the same dictionaries for name, city, state, and country values.

create table flights (
*
*
*
dest_name TEXT ENCODING DICT,
dest_city TEXT ENCODING DICT,
dest_state TEXT ENCODING DICT,
dest_country TEXT ENCODING DICT,

*
*
*
origin_name TEXT,
origin_city TEXT,
origin_state TEXT,
origin_country TEXT,
*
*
*

SHARED DICTIONARY (origin_name) REFERENCES flights(dest_name),
SHARED DICTIONARY (origin_city) REFERENCES flights(dest_city),
SHARED DICTIONARY (origin_state) REFERENCES flights(dest_state),
SHARED DICTIONARY (origin_country) REFERENCES flights(dest_country),
*
*
*
)
WITH(
*
*
*
)

To share a dictionary in a different existing table, replace the table name in the REFERENCES instruction. For example, if you have an existing table called us_geography, you can share the dictionary by following the pattern in the DDL fragment below.

create table flights (

*
*
*

SHARED DICTIONARY (origin_city) REFERENCES us_geography(city),
SHARED DICTIONARY (origin_state) REFERENCES us_geography(state),
SHARED DICTIONARY (origin_country) REFERENCES us_geography(country),
SHARED DICTIONARY (dest_city) REFERENCES us_geography(city),
SHARED DICTIONARY (dest_state) REFERENCES us_geography(state),
SHARED DICTIONARY (dest_country) REFERENCES us_geography(country),

*
*
*
)
WITH(
*
*
*
);

NOTE: The referencing column cannot specify the encoding of the dictionary because it uses the encoding from the referenced column.