fix: eager source row fetching logic (#2071) #52
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This is an old bug which could only surface with the more recent addition of custom Cypher queries. The template tries to pre-fetch source data. It does it for text sources, since they do not support SQL pushdown, so their data is required for post-processing anyway. Before this commit, the template also pre-fetched data when none of the source's targets defined source transformations. This is overly restrictive and actually wrong. Custom query targets cannot define source transformations. If they share a source with a node/rel targets that define custom source transformations, then the template would crash with a NPE. This is now fixed. Source data is pre-fetched as long as there is at least one of its target that does not define any transformation. The commit also adds another small optimization: if the source does not match any active targets, the source processing is skipped completely. Before that, the data could be pre-fetched, incurring unnecessary data movement.
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This is an old bug which could only surface with the more recent addition of custom Cypher queries.
The template tries to pre-fetch source data.
It does it for text sources, since they do not support SQL pushdown, so their data is required for post-processing anyway.
Before this commit, the template also pre-fetched data when none of the source's targets defined source transformations.
This is overly restrictive and actually wrong.
Custom query targets cannot define source transformations.
If they share a source with a node/rel targets that define custom source transformations, then the template would crash with a NPE.
This is now fixed. Source data is pre-fetched as long as there is at least one of its target that does not define any transformation.
The commit also adds another small optimization: if the source does not match any active targets, the source processing is skipped completely. Before that, the data could be pre-fetched, incurring unnecessary data movement.