Store tags in compressed segments instead of in the metadata Delta Lake#293
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Store tags in compressed segments instead of in the metadata Delta Lake#293
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chrthomsen
approved these changes
Feb 28, 2025
skejserjensen
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Mar 2, 2025
This was referenced Mar 5, 2025
skejserjensen
approved these changes
Mar 6, 2025
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This PR implements #197 by storing tags in the compressed segments instead of in the metadata Delta Lake and removing univariate ids from the entire code base.
The ingestion process has been updated to no longer lookup and save the tag hash using the table metadata manager when inserting data points. Instead, we calculate a tag hash in the uncompressed data manager that is only used internally for managing uncompressed multivariate time series during ingestion. This tag hash is not used beyond compression since the compressed segments are stored per table.
Compression has been updated to no longer store the univariate id in the compressed segments and instead store the tag columns. The compressed data manager has also been updated so we now use the tag columns for sorting instead of the univariate id when saving data to disk.
The query process has also been updated accordingly.
ParquetExecnow uses a schema that is based on the specific model table,GridExecreconstructs data points that includes the tag columns in each row, andSortedJoinExecnow reconstructs the query result in the wanted return order using the tag columns in the first field column instead of using the metadata Delta Lake.It should be noted that the objective of this PR is to implement the base functionality for tags in data meaning further optimizations are required. #292 has been created to look into further optimizations.