Handling large binary data in Azure Synapse
When dealing with large binary data types like geography or image data in Azure Synapse, you may encounter challenges due to limitations in supported data types and column sizes. Let's take the example of a City table with a Location column holding geography data, which needs to be converted to a varbinary type during loading since Azure Synapse doesn't natively support geography types.
Example:
1. Convert to varbinary: During loading, convert the geography data to varbinary.
2. Data Chunking: Since PolyBase supports varbinary up to 8000 bytes, data may get truncated. To overcome this, split the data into manageable chunks.
3. Temporary Staging: Create a temporary staging table for the Location column.
4. Chunk Processing: Split the location data into 8000-byte chunks for each city, resulting in 1 to N rows for each city.
5. Reassembly: Reassemble the chunks using T-SQL PIVOT operator to convert rows into columns and concatenate column values for each city.
6. Row Padding: Ensure every city has the same number of rows for PIVOT operation to work. Pad rows with blank values as needed.
7. Performance Optimization: Utilize T-SQL query tricks to speed up the process, making it more efficient than looping through rows individually.
This approach can also be applied to handle image data efficiently. By breaking down the data into manageable chunks and reassembling them using T-SQL operations, you can effectively manage large binary data in Azure Synapse.
Handling large binary data in Azure Synapse - Example T-SQL Code:
Here's an example T-SQL code demonstrating how to handle large binary data in Azure Synapse:
```sql
-- Step 1: Create temporary staging table for Location column
CREATE TABLE dbo.LocationStaging (
CityID INT,
ChunkID INT,
LocationVarbinary VARBINARY(MAX)
);
-- Step 2: Split geography data into 8000-byte chunks and insert into staging table
INSERT INTO dbo.LocationStaging (CityID, ChunkID, LocationVarbinary)
SELECT
CityID,
ROW_NUMBER() OVER (PARTITION BY CityID ORDER BY (SELECT NULL)) AS ChunkID,
CONVERT(VARBINARY(MAX), SUBSTRING(CONVERT(VARCHAR(MAX), Location), (ChunkID - 1) * 8000 + 1, 8000))
FROM City;
-- Step 3: Reassemble chunks using PIVOT and concatenate
WITH ChunkedData AS (
SELECT
CityID,
ChunkID,
LocationVarbinary,
'Chunk' + CAST(ROW_NUMBER() OVER (PARTITION BY CityID ORDER BY ChunkID) AS VARCHAR(10)) AS ChunkColumn
FROM dbo.LocationStaging
)
SELECT CityID, [Chunk1], [Chunk2], [Chunk3], ... -- Add more columns as needed
FROM ChunkedData
PIVOT (
MAX(LocationVarbinary) FOR ChunkColumn IN ([Chunk1], [Chunk2], [Chunk3], ...) -- Add more columns as needed
) AS PivotedData;
-- Step 4: Optionally drop temporary staging table
DROP TABLE dbo.LocationStaging;
```
This code outlines the process of splitting geography data into 8000-byte chunks, storing them in a temporary staging table, reassembling them using PIVOT operation, and finally dropping the temporary staging table. Adjust the code as per your specific requirements and table structures.
