The following examples write all the data stored in a database table to external object storage. The data is partitioned (sorted) by Advanced SQL Engine before being written. The objects containing the data in external storage are named to reflect the sorted data they contain.
- If not already done, set up an authorization to access external object store. See Setting Up Authorization for WRITE_NOS Examples.
- If not already done, set up a database table to extract data from. You can use one of your existing tables or set up a test table to use with the examples. See Setting Up a Test Table.
- If not already done, set up or obtain access to the external object store where you want to write data. Follow the instructions from your external storage vendor.
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Write all the rows from a database table to external object store:
SELECT NodeId, AmpId, Sequence, ObjectName, ObjectSize, RecordCount FROM WRITE_NOS_FM ( ON ( SELECT * FROM RiverFlowPerm ) PARTITION BY SiteNo ORDER BY SiteNo USING LOCATION('YOUR-STORAGE-ACCOUNT/RiverFlowPerm/') STOREDAS('PARQUET') COMPRESSION('GZIP') NAMING('RANGE') INCLUDE_ORDERING('TRUE') MAXOBJECTSIZE('4MB') ) AS d ORDER BY AmpId;
Replace LOCATION with the URI to the external object store where you are writing the data.
Things to note in this example:- Each row of the result set describes one object written to external storage that contains data from Advanced SQL Engine.
- Each object contains data from one partition created according to the PARTITION BY clause. In this case there is one partition for each data collection site, that is, for each SiteNo column value.
- NAMING('RANGE') causes the object names to include the upper and lower values in the range. In this case the object names include the values for SiteNo. For example, in the object name, /S3/s3.amazonaws.com/ie-writenos-bucket/RiverFlowPerm/09497500/09497500/object_33_0_1.parquet, "09497500" is the SiteNo of the data contained by this object. This object contains data from multiple site numbers between sites 09497500 and 09497500, inclusive.
- Because the query included INCLUDE_ORDERING('TRUE'), the objects include data from the ORDER BY column(s), in this case the object data includes the site number from which the data in that row was collected.
Your result will be similar to the following:
NodeId 33 AmpId 0 Sequence 1 ObjectName /S3/s3.amazonaws.com/ie-writenos-bucket/RiverFlowPerm/09497500/09497500/object_33_0_1.parquet ObjectSize 27682 RecordCount 2944 NodeId 33 AmpId 0 Sequence 1 ObjectName /S3/s3.amazonaws.com/ie-writenos-bucket/RiverFlowPerm/09513780/09513780/object_33_0_1.parquet ObjectSize 19136 RecordCount 2941 [...]
For readability, the output is displayed vertically.
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Verify the offloaded data on external object storage:
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Create a foreign table to access external object store:
CREATE FOREIGN TABLE ftRiverFlowPerm, EXTERNAL SECURITY DEFINER TRUSTED DefAuth_Write ( Location VARCHAR(2048) CHARACTER SET UNICODE CASESPECIFIC, SiteNo VARCHAR(8) CHARACTER SET UNICODE, DateTime TIMESTAMP(0) FORMAT 'YYYY-MM-DDBHH:MI', Flow FLOAT, GageHeight1 FLOAT, Precipitation FLOAT, Temperature FLOAT, Velocity FLOAT, BatteryVoltage FLOAT, GageHeight2 FLOAT, WaterVelocity FLOAT, Conductance FLOAT ) USING ( LOCATION('YOUR-STORAGE-ACCOUNT/RiverFlowPerm/') STOREDAS('PARQUET') ) PARTITION BY COLUMN;
Replace LOCATION with the URI to the external object store where you wrote the data.
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Count the number of rows in the external data:
SELECT COUNT(*) FROM ftRiverFlowPerm;
Result:Count(*) -------- 36301
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Sample one row from the external data using the foreign table called ftRiverFlowPerm:
SELECT * FROM ftRiverFlowPerm SAMPLE 1;
Result:Location /S3/s3.amazonaws.com/ie-writenos-bucket/RiverFlowPerm/09429070/09429070/object_33_1_1.parquet SiteNo 09429070 DateTime 2018-07-16 22:00 Flow 1.55000000000000E 002 GageHeight1 4.38000000000000E 000 Precipitation ? Temperature 8.33000000000000E 001 Velocity 1.15000000000000E 000 BatteryVoltage ? GageHeight2 ? WaterVelocity ? Conductance ?
For readability, the output is displayed vertically.
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Create a foreign table to access external object store:
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Write all the rows from a database table to external object store:
SELECT NodeId, AmpId, Sequence, ObjectName, ObjectSize, RecordCount FROM WRITE_NOS_FM ( ON ( SELECT * FROM RiverFlowPerm ) PARTITION BY SiteNo ORDER BY SiteNo USING LOCATION('YOUR-STORAGE-ACCOUNT/RiverFlowPerm_Discrete/') STOREDAS('PARQUET') COMPRESSION('GZIP') NAMING('DISCRETE') INCLUDE_ORDERING('TRUE') MAXOBJECTSIZE('4MB') ) AS d ORDER BY AmpId;
Replace LOCATION with the URI to the external object store where you want to write the data.
Things to note in this example:- Each row of the result set describes one object written to external storage that contains data from Vantage.
- Each object contains data from one partition created according to the PARTITION BY clause. In this case there is one partition for each data collection site, that is, for each SiteNo column value.
- NAMING('DISCRETE') causes the object names to include the partition name, in this case the object names include the values for SiteNo. In the object name, /S3/s3.amazonaws.com/ie-writenos-bucket/RiverFlowPerm_Discrete/09497500/object_33_0_1.parquet, "09497500" is the SiteNo of the data contained by this object.
- Because the query included INCLUDE_ORDERING('TRUE'), the objects include data from the ORDER BY column(s), in this case the object data includes the site number from which the data in that row was collected.
Your result will be similar to the following:
NodeId 33 AmpId 0 Sequence 1 ObjectName /S3/s3.amazonaws.com/ie-writenos-bucket/RiverFlowPerm_Discrete/09497500/object_33_0_1.parquet ObjectSize 27682 RecordCount 2944 NodeId 33 AmpId 0 Sequence 1 ObjectName /S3/s3.amazonaws.com/ie-writenos-bucket/RiverFlowPerm_Discrete/09513780/object_33_0_1.parquet ObjectSize 19136 RecordCount 2941 NodeId 33 AmpId 0 Sequence 1 ObjectName /S3/s3.amazonaws.com/ie-writenos-bucket/RiverFlowPerm_Discrete/09424900/object_33_0_1.parquet ObjectSize 23174 RecordCount 2946 [...]
For readability the output is displayed vertically.
Prerequisites
Example: Write All Rows to External Object Store, Use PARTITION BY and NAMING('RANGE')
Example: Write All Rows to External Object Store, Use PARTITION BY and NAMING('DISCRETE')