DML Operations on CarbonData

This tutorial will guide you through the data manipulation language support provided by CarbonData.

Overview

The following DML operations are supported in CarbonData :

LOAD DATA
SHOW SEGMENTS
DELETE SEGMENT BY ID
DELETE SEGMENT BY DATE

LOAD DATA

This command loads the user data in raw format to the Carbon specific data format store, this allows Carbon to provides good performance while querying the data. Please visit Data Management for more details on LOAD.

Syntax

LOAD DATA [LOCAL] INPATH 'folder_path' INTO TABLE [db_name.]table_name OPTIONS(property_name=property_value, ...)

OPTIONS are not mandatory for data loading process. Inside OPTIONS user can provide either of any options like DELIMITER,QUOTECHAR, ESCAPECHAR,MULTILINE as per requirement.

Note: The path shall be canonical path.

Parameter Description

Parameter	Description	Optional
folder_path	Path of raw csv data folder or file.	NO
db_name	Database name, if it is not specified then it uses current database.	YES
table_name	The name of the table in provided database.	NO
OPTIONS	Extra options provided to Load	YES

Usage Guideline

Following are the options that can be used for loading data:

DELIMITER: Delimiters can be provided in the load command.
```
OPTIONS('DELIMITER'=',')
```
QUOTECHAR: Quote Characters can be provided in the load command.
```
OPTIONS('QUOTECHAR'='"')
```
COMMENTCHAR: Comment Characters can be provided in the load command if user want to comment lines.
```
OPTIONS('COMMENTCHAR'='#')
```
FILEHEADER: Headers can be provided in the LOAD DATA command if headers are missing in the source files.
```
OPTIONS('FILEHEADER'='column1,column2') 
```
MULTILINE: CSV with new line character in quotes.
```
OPTIONS('MULTILINE'='true') 
```
ESCAPECHAR: Escape char can be provided if user want strict validation of escape character on CSV.
```
OPTIONS('ESCAPECHAR'='\') 
```
COMPLEX_DELIMITER_LEVEL_1: Split the complex type data column in a row (eg., a$b$c --> Array = {a,b,c}).
```
OPTIONS('COMPLEX_DELIMITER_LEVEL_1'='$') 
```
COMPLEX_DELIMITER_LEVEL_2: Split the complex type nested data column in a row. Applies level_1 delimiter & applies level_2 based on complex data type (eg., a:b$c:d --> Array> = {{a,b},{c,d}}).
```
OPTIONS('COMPLEX_DELIMITER_LEVEL_2'=':') 
```

ALL_DICTIONARY_PATH: All dictionary files path.

OPTIONS('ALL_DICTIONARY_PATH'='/opt/alldictionary/data.dictionary')

COLUMNDICT: Dictionary file path for specified column.
```
OPTIONS('COLUMNDICT'='column1:dictionaryFilePath1, column2:dictionaryFilePath2')
```
Note: ALL_DICTIONARY_PATH and COLUMNDICT can't be used together.
DATEFORMAT: Date format for specified column.
```
OPTIONS('DATEFORMAT'='column1:dateFormat1, column2:dateFormat2')
```
Note: Date formats are specified by date pattern strings. The date pattern letters in Carbon are the same as in JAVA. Refer to SimpleDateFormat.

Example:

LOAD DATA local inpath '/opt/rawdata/data.csv' INTO table carbontable
                         options('DELIMITER'=',', 'QUOTECHAR'='"', 'COMMENTCHAR'='#',
                                 'FILEHEADER'='empno,empname,
 designation,doj,workgroupcategory,
 workgroupcategoryname,deptno,deptname,projectcode,
 projectjoindate,projectenddate,attendance,utilization,salary',
                                 'MULTILINE'='true', 'ESCAPECHAR'='\', 
 'COMPLEX_DELIMITER_LEVEL_1'='$', 
                                 'COMPLEX_DELIMITER_LEVEL_2'=':',
                                 'ALL_DICTIONARY_PATH'='/opt/alldictionary/data.dictionary'
                                 )

SHOW SEGMENTS

This command is used to get the segments of carbon table.

SHOW SEGMENTS FOR TABLE [db_name.]table_name LIMIT number_of_segments;

Parameter Description

Parameter	Description	Optional
db_name	Database name, if it is not specified then it uses current database.	YES
table_name	The name of the table in provided database.	NO
number_of_segments	limit the output to this number.	YES

Example:

SHOW SEGMENTS FOR TABLE CarbonDatabase.CarbonTable LIMIT 4;

DELETE SEGMENT BY ID

This command is used to delete segment by using the segment ID. Each segment has a unique segment ID associated with it. Using this segment ID, you can remove the segment.

The following command will get the segmentID.

SHOW SEGMENTS FOR Table dbname.tablename LIMIT number_of_segments

After you retrieve the segment ID of the segment that you want to delete, execute the following command to delete the selected segment.

DELETE SEGMENT segment_sequence_id1, segments_sequence_id2, .... FROM TABLE tableName

Parameter Description

Parameter	Description	Optional
segment_id	Segment Id of the load.	NO
db_name	Database name, if it is not specified then it uses current database.	YES
table_name	The name of the table in provided database.	NO

Example:

DELETE SEGMENT 0 FROM TABLE CarbonDatabase.CarbonTable;
DELETE SEGMENT 0.1,5,8 FROM TABLE CarbonDatabase.CarbonTable;

Note: Here 0.1 is compacted segment sequence id.

DELETE SEGMENT BY DATE

This command will allow to delete the Carbon segment(s) from the store based on the date provided by the user in the DML command. The segment created before the particular date will be removed from the specific stores.

DELETE FROM TABLE [schema_name.]table_name WHERE[DATE_FIELD]BEFORE [DATE_VALUE]

Parameter Description

Parameter	Description	Optional
DATE_VALUE	Valid segement load start time value. All the segments before this specified date will be deleted.	NO
db_name	Database name, if it is not specified then it uses current database.	YES
table_name	The name of the table in provided database.	NO

Example:

DELETE SEGMENTS FROM TABLE CarbonDatabase.CarbonTable WHERE STARTTIME BEFORE '2017-06-01 12:05:06';