Spark 4.0, Core: Add Limit pushdown to Scan #14615
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nastra
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singhpk234
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| public ThisT minRowsRequested(int numRows) { | ||
| return newRefinedScan(table, schema, context.minRowsRequested(numRows)); | ||
| } |
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| public ThisT minRowsRequested(int numRows) { | |
| return newRefinedScan(table, schema, context.minRowsRequested(numRows)); | |
| } | |
| public ThisT minRowsRequested(Integer numRows) { | |
| return newRefinedScan(table, schema, context.minRowsRequested(numRows)); | |
| } |
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why would we want to make this an Integer instead of an int?
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| /** | ||
| * Create a new scan that returns files with at least the given number of rows. This is used as a | ||
| * hint during server-side scan planning to not have to return more rows than necessary. It is not |
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why only server-side scan planning, we can extend this to any scan ?
if the intention is strictly to make it for server-side scan i would recommend another interface which implementation can implement both Scan and LimitAwareScan (?)
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Yeah, but also this is a lot lighter than the open PR #13451 that adds some local optimizations for non rest catalogs.
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I've removed that wording to not limit this to server-side scan planning
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This pushes down the
LIMITfrom Spark to the underlying Scan. This is still expecting theLIMITto be applied by Spark, but its value is pushed down through the Scan and used asmin-rows-requested(introduced by #14565) for server-side scan planning. This is used as a hint during server-side scan planning to not have to return more rows than necessary. It is not required for the server to return that many rows since the scan may not produce that many rows. The server can also return more rows than requested.