[jira] [Updated] (HIVE-8038) Decouple ORC files split calculation logic from Filesystem's get file location implementation
[ https://issues.apache.org/jira/browse/HIVE-8038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Gopal V updated HIVE-8038: -- Resolution: Fixed Release Note: HIVE-8038: Decouple ORC files split calculation logic from fixed-size block assumptions. (Pankit Thapar via Gopal V) Status: Resolved (was: Patch Available) Committed to trunk, thanks [~pankit] > Decouple ORC files split calculation logic from Filesystem's get file > location implementation > - > > Key: HIVE-8038 > URL: https://issues.apache.org/jira/browse/HIVE-8038 > Project: Hive > Issue Type: Improvement > Components: File Formats >Affects Versions: 0.13.1 >Reporter: Pankit Thapar >Assignee: Pankit Thapar > Fix For: 0.14.0 > > Attachments: HIVE-8038.2.patch, HIVE-8038.3.patch, HIVE-8038.patch > > > What is the Current Logic > == > 1.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using the array index (index = > offset/blockSize), get the corresponding host having the blockLocation > 4.If the split spans multiple blocks, then get all hosts that have at least > 80% of the max of total data in split hosted by any host. > 5.add the split to a list of splits > Issue with Current Logic > = > Dependency on FileSystem API’s logic for block location calculations. It > returns an array and we need to rely on FileSystem to > make all blocks of same size if we want to directly access a block from the > array. > > What is the Fix > = > 1a.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 1b.convert the array into a tree map and return it > through getLocationsWithOffSet() > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using Tree.floorEntry(key), get the > highest entry smaller than offset for the split and get the corresponding > host. > 4a.If the split spans multiple blocks, get a submap, which contains all > entries containing blockLocations from the offset to offset + length > 4b.get all hosts that have at least 80% of the max of total data in split > hosted by any host. > 5.add the split to a list of splits > What are the major changes in logic > == > 1. store BlockLocations in a Map instead of an array > 2. Call SHIMS.getLocationsWithOffSet() instead of getLocations() > 3. one block case is checked by "if(offset + length <= start.getOffset() + > start.getLength())" instead of "if((offset % blockSize) + length <= > blockSize)" > What is the affect on Complexity (Big O) > = > 1. We add a O(n) loop to build a TreeMap from an array but its a one time > cost and would not be called for each split > 2. In case of one block case, we can get the block in O(logn) worst case > which was O(1) before > 3. Getting the submap is O(logn) > 4. In case of multiple block case, building the list of hosts is O(m) which > was O(n) & m < n as previously we were iterating >over all the block locations but now we are only iterating only blocks > that belong to that range go offsets that we need. > What are the benefits of the change > == > 1. With this fix, we do not depend on the blockLocations returned by > FileSystem to figure out the block corresponding to the offset and blockSize > 2. Also, it is not necessary that block lengths is same for all blocks for > all FileSystems > 3. Previously we were using blockSize for one block case and block.length for > multiple block case, which is not the case now. We figure out the block >depending upon the actual length and offset of the block -- This message was sent by Atlassian JIRA (v6.3.4#6332)
[jira] [Updated] (HIVE-8038) Decouple ORC files split calculation logic from Filesystem's get file location implementation
[
https://issues.apache.org/jira/browse/HIVE-8038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Gopal V updated HIVE-8038:
--
Attachment: HIVE-8038.3.patch
+1 - Patch looks good.
For commit - .3.patch, removed a white space change & a javadoc.
{code}
context.splits.add(new OrcSplit(file.getPath(), offset, length,
-hosts, fileMetaInfo, isOriginal, hasBase, deltas));
+hosts, fileMetaInfo, isOriginal, hasBase, deltas));
}
...
- * @return TreeMap
+ * @return TreeMap
{code}
> Decouple ORC files split calculation logic from Filesystem's get file
> location implementation
> -
>
> Key: HIVE-8038
> URL: https://issues.apache.org/jira/browse/HIVE-8038
> Project: Hive
> Issue Type: Improvement
> Components: File Formats
>Affects Versions: 0.13.1
>Reporter: Pankit Thapar
>Assignee: Pankit Thapar
> Fix For: 0.14.0
>
> Attachments: HIVE-8038.2.patch, HIVE-8038.3.patch, HIVE-8038.patch
>
>
> What is the Current Logic
> ==
> 1.get the file blocks from FileSystem.getFileBlockLocations() which returns
> an array of BlockLocation
> 2.In SplitGenerator.createSplit(), check if split only spans one block or
> multiple blocks.
> 3.If split spans just one block, then using the array index (index =
> offset/blockSize), get the corresponding host having the blockLocation
> 4.If the split spans multiple blocks, then get all hosts that have at least
> 80% of the max of total data in split hosted by any host.
> 5.add the split to a list of splits
> Issue with Current Logic
> =
> Dependency on FileSystem API’s logic for block location calculations. It
> returns an array and we need to rely on FileSystem to
> make all blocks of same size if we want to directly access a block from the
> array.
>
> What is the Fix
> =
> 1a.get the file blocks from FileSystem.getFileBlockLocations() which returns
> an array of BlockLocation
> 1b.convert the array into a tree map and return it
> through getLocationsWithOffSet()
> 2.In SplitGenerator.createSplit(), check if split only spans one block or
> multiple blocks.
> 3.If split spans just one block, then using Tree.floorEntry(key), get the
> highest entry smaller than offset for the split and get the corresponding
> host.
> 4a.If the split spans multiple blocks, get a submap, which contains all
> entries containing blockLocations from the offset to offset + length
> 4b.get all hosts that have at least 80% of the max of total data in split
> hosted by any host.
> 5.add the split to a list of splits
> What are the major changes in logic
> ==
> 1. store BlockLocations in a Map instead of an array
> 2. Call SHIMS.getLocationsWithOffSet() instead of getLocations()
> 3. one block case is checked by "if(offset + length <= start.getOffset() +
> start.getLength())" instead of "if((offset % blockSize) + length <=
> blockSize)"
> What is the affect on Complexity (Big O)
> =
> 1. We add a O(n) loop to build a TreeMap from an array but its a one time
> cost and would not be called for each split
> 2. In case of one block case, we can get the block in O(logn) worst case
> which was O(1) before
> 3. Getting the submap is O(logn)
> 4. In case of multiple block case, building the list of hosts is O(m) which
> was O(n) & m < n as previously we were iterating
>over all the block locations but now we are only iterating only blocks
> that belong to that range go offsets that we need.
> What are the benefits of the change
> ==
> 1. With this fix, we do not depend on the blockLocations returned by
> FileSystem to figure out the block corresponding to the offset and blockSize
> 2. Also, it is not necessary that block lengths is same for all blocks for
> all FileSystems
> 3. Previously we were using blockSize for one block case and block.length for
> multiple block case, which is not the case now. We figure out the block
>depending upon the actual length and offset of the block
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[jira] [Updated] (HIVE-8038) Decouple ORC files split calculation logic from Filesystem's get file location implementation
[ https://issues.apache.org/jira/browse/HIVE-8038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Gopal V updated HIVE-8038: -- Status: Open (was: Patch Available) > Decouple ORC files split calculation logic from Filesystem's get file > location implementation > - > > Key: HIVE-8038 > URL: https://issues.apache.org/jira/browse/HIVE-8038 > Project: Hive > Issue Type: Improvement > Components: File Formats >Affects Versions: 0.13.1 >Reporter: Pankit Thapar >Assignee: Pankit Thapar > Fix For: 0.14.0 > > Attachments: HIVE-8038.2.patch, HIVE-8038.patch > > > What is the Current Logic > == > 1.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using the array index (index = > offset/blockSize), get the corresponding host having the blockLocation > 4.If the split spans multiple blocks, then get all hosts that have at least > 80% of the max of total data in split hosted by any host. > 5.add the split to a list of splits > Issue with Current Logic > = > Dependency on FileSystem API’s logic for block location calculations. It > returns an array and we need to rely on FileSystem to > make all blocks of same size if we want to directly access a block from the > array. > > What is the Fix > = > 1a.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 1b.convert the array into a tree map and return it > through getLocationsWithOffSet() > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using Tree.floorEntry(key), get the > highest entry smaller than offset for the split and get the corresponding > host. > 4a.If the split spans multiple blocks, get a submap, which contains all > entries containing blockLocations from the offset to offset + length > 4b.get all hosts that have at least 80% of the max of total data in split > hosted by any host. > 5.add the split to a list of splits > What are the major changes in logic > == > 1. store BlockLocations in a Map instead of an array > 2. Call SHIMS.getLocationsWithOffSet() instead of getLocations() > 3. one block case is checked by "if(offset + length <= start.getOffset() + > start.getLength())" instead of "if((offset % blockSize) + length <= > blockSize)" > What is the affect on Complexity (Big O) > = > 1. We add a O(n) loop to build a TreeMap from an array but its a one time > cost and would not be called for each split > 2. In case of one block case, we can get the block in O(logn) worst case > which was O(1) before > 3. Getting the submap is O(logn) > 4. In case of multiple block case, building the list of hosts is O(m) which > was O(n) & m < n as previously we were iterating >over all the block locations but now we are only iterating only blocks > that belong to that range go offsets that we need. > What are the benefits of the change > == > 1. With this fix, we do not depend on the blockLocations returned by > FileSystem to figure out the block corresponding to the offset and blockSize > 2. Also, it is not necessary that block lengths is same for all blocks for > all FileSystems > 3. Previously we were using blockSize for one block case and block.length for > multiple block case, which is not the case now. We figure out the block >depending upon the actual length and offset of the block -- This message was sent by Atlassian JIRA (v6.3.4#6332)
[jira] [Updated] (HIVE-8038) Decouple ORC files split calculation logic from Filesystem's get file location implementation
[ https://issues.apache.org/jira/browse/HIVE-8038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Gopal V updated HIVE-8038: -- Status: Patch Available (was: Open) Resubmitting to run tests again. > Decouple ORC files split calculation logic from Filesystem's get file > location implementation > - > > Key: HIVE-8038 > URL: https://issues.apache.org/jira/browse/HIVE-8038 > Project: Hive > Issue Type: Improvement > Components: File Formats >Affects Versions: 0.13.1 >Reporter: Pankit Thapar >Assignee: Pankit Thapar > Fix For: 0.14.0 > > Attachments: HIVE-8038.2.patch, HIVE-8038.patch > > > What is the Current Logic > == > 1.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using the array index (index = > offset/blockSize), get the corresponding host having the blockLocation > 4.If the split spans multiple blocks, then get all hosts that have at least > 80% of the max of total data in split hosted by any host. > 5.add the split to a list of splits > Issue with Current Logic > = > Dependency on FileSystem API’s logic for block location calculations. It > returns an array and we need to rely on FileSystem to > make all blocks of same size if we want to directly access a block from the > array. > > What is the Fix > = > 1a.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 1b.convert the array into a tree map and return it > through getLocationsWithOffSet() > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using Tree.floorEntry(key), get the > highest entry smaller than offset for the split and get the corresponding > host. > 4a.If the split spans multiple blocks, get a submap, which contains all > entries containing blockLocations from the offset to offset + length > 4b.get all hosts that have at least 80% of the max of total data in split > hosted by any host. > 5.add the split to a list of splits > What are the major changes in logic > == > 1. store BlockLocations in a Map instead of an array > 2. Call SHIMS.getLocationsWithOffSet() instead of getLocations() > 3. one block case is checked by "if(offset + length <= start.getOffset() + > start.getLength())" instead of "if((offset % blockSize) + length <= > blockSize)" > What is the affect on Complexity (Big O) > = > 1. We add a O(n) loop to build a TreeMap from an array but its a one time > cost and would not be called for each split > 2. In case of one block case, we can get the block in O(logn) worst case > which was O(1) before > 3. Getting the submap is O(logn) > 4. In case of multiple block case, building the list of hosts is O(m) which > was O(n) & m < n as previously we were iterating >over all the block locations but now we are only iterating only blocks > that belong to that range go offsets that we need. > What are the benefits of the change > == > 1. With this fix, we do not depend on the blockLocations returned by > FileSystem to figure out the block corresponding to the offset and blockSize > 2. Also, it is not necessary that block lengths is same for all blocks for > all FileSystems > 3. Previously we were using blockSize for one block case and block.length for > multiple block case, which is not the case now. We figure out the block >depending upon the actual length and offset of the block -- This message was sent by Atlassian JIRA (v6.3.4#6332)
[jira] [Updated] (HIVE-8038) Decouple ORC files split calculation logic from Filesystem's get file location implementation
[ https://issues.apache.org/jira/browse/HIVE-8038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Gopal V updated HIVE-8038: -- Assignee: Pankit Thapar > Decouple ORC files split calculation logic from Filesystem's get file > location implementation > - > > Key: HIVE-8038 > URL: https://issues.apache.org/jira/browse/HIVE-8038 > Project: Hive > Issue Type: Improvement > Components: File Formats >Affects Versions: 0.13.1 >Reporter: Pankit Thapar >Assignee: Pankit Thapar > Fix For: 0.14.0 > > Attachments: HIVE-8038.2.patch, HIVE-8038.patch > > > What is the Current Logic > == > 1.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using the array index (index = > offset/blockSize), get the corresponding host having the blockLocation > 4.If the split spans multiple blocks, then get all hosts that have at least > 80% of the max of total data in split hosted by any host. > 5.add the split to a list of splits > Issue with Current Logic > = > Dependency on FileSystem API’s logic for block location calculations. It > returns an array and we need to rely on FileSystem to > make all blocks of same size if we want to directly access a block from the > array. > > What is the Fix > = > 1a.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 1b.convert the array into a tree map and return it > through getLocationsWithOffSet() > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using Tree.floorEntry(key), get the > highest entry smaller than offset for the split and get the corresponding > host. > 4a.If the split spans multiple blocks, get a submap, which contains all > entries containing blockLocations from the offset to offset + length > 4b.get all hosts that have at least 80% of the max of total data in split > hosted by any host. > 5.add the split to a list of splits > What are the major changes in logic > == > 1. store BlockLocations in a Map instead of an array > 2. Call SHIMS.getLocationsWithOffSet() instead of getLocations() > 3. one block case is checked by "if(offset + length <= start.getOffset() + > start.getLength())" instead of "if((offset % blockSize) + length <= > blockSize)" > What is the affect on Complexity (Big O) > = > 1. We add a O(n) loop to build a TreeMap from an array but its a one time > cost and would not be called for each split > 2. In case of one block case, we can get the block in O(logn) worst case > which was O(1) before > 3. Getting the submap is O(logn) > 4. In case of multiple block case, building the list of hosts is O(m) which > was O(n) & m < n as previously we were iterating >over all the block locations but now we are only iterating only blocks > that belong to that range go offsets that we need. > What are the benefits of the change > == > 1. With this fix, we do not depend on the blockLocations returned by > FileSystem to figure out the block corresponding to the offset and blockSize > 2. Also, it is not necessary that block lengths is same for all blocks for > all FileSystems > 3. Previously we were using blockSize for one block case and block.length for > multiple block case, which is not the case now. We figure out the block >depending upon the actual length and offset of the block -- This message was sent by Atlassian JIRA (v6.3.4#6332)
[jira] [Updated] (HIVE-8038) Decouple ORC files split calculation logic from Filesystem's get file location implementation
[ https://issues.apache.org/jira/browse/HIVE-8038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Pankit Thapar updated HIVE-8038: Attachment: HIVE-8038.2.patch Attached the fixed patch as per CR : https://reviews.apache.org/r/25521/ > Decouple ORC files split calculation logic from Filesystem's get file > location implementation > - > > Key: HIVE-8038 > URL: https://issues.apache.org/jira/browse/HIVE-8038 > Project: Hive > Issue Type: Improvement > Components: File Formats >Affects Versions: 0.13.1 >Reporter: Pankit Thapar > Fix For: 0.14.0 > > Attachments: HIVE-8038.2.patch, HIVE-8038.patch > > > What is the Current Logic > == > 1.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using the array index (index = > offset/blockSize), get the corresponding host having the blockLocation > 4.If the split spans multiple blocks, then get all hosts that have at least > 80% of the max of total data in split hosted by any host. > 5.add the split to a list of splits > Issue with Current Logic > = > Dependency on FileSystem API’s logic for block location calculations. It > returns an array and we need to rely on FileSystem to > make all blocks of same size if we want to directly access a block from the > array. > > What is the Fix > = > 1a.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 1b.convert the array into a tree map and return it > through getLocationsWithOffSet() > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using Tree.floorEntry(key), get the > highest entry smaller than offset for the split and get the corresponding > host. > 4a.If the split spans multiple blocks, get a submap, which contains all > entries containing blockLocations from the offset to offset + length > 4b.get all hosts that have at least 80% of the max of total data in split > hosted by any host. > 5.add the split to a list of splits > What are the major changes in logic > == > 1. store BlockLocations in a Map instead of an array > 2. Call SHIMS.getLocationsWithOffSet() instead of getLocations() > 3. one block case is checked by "if(offset + length <= start.getOffset() + > start.getLength())" instead of "if((offset % blockSize) + length <= > blockSize)" > What is the affect on Complexity (Big O) > = > 1. We add a O(n) loop to build a TreeMap from an array but its a one time > cost and would not be called for each split > 2. In case of one block case, we can get the block in O(logn) worst case > which was O(1) before > 3. Getting the submap is O(logn) > 4. In case of multiple block case, building the list of hosts is O(m) which > was O(n) & m < n as previously we were iterating >over all the block locations but now we are only iterating only blocks > that belong to that range go offsets that we need. > What are the benefits of the change > == > 1. With this fix, we do not depend on the blockLocations returned by > FileSystem to figure out the block corresponding to the offset and blockSize > 2. Also, it is not necessary that block lengths is same for all blocks for > all FileSystems > 3. Previously we were using blockSize for one block case and block.length for > multiple block case, which is not the case now. We figure out the block >depending upon the actual length and offset of the block -- This message was sent by Atlassian JIRA (v6.3.4#6332)
[jira] [Updated] (HIVE-8038) Decouple ORC files split calculation logic from Filesystem's get file location implementation
[ https://issues.apache.org/jira/browse/HIVE-8038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Pankit Thapar updated HIVE-8038: Status: Patch Available (was: Open) > Decouple ORC files split calculation logic from Filesystem's get file > location implementation > - > > Key: HIVE-8038 > URL: https://issues.apache.org/jira/browse/HIVE-8038 > Project: Hive > Issue Type: Improvement > Components: File Formats >Affects Versions: 0.13.1 >Reporter: Pankit Thapar > Fix For: 0.14.0 > > Attachments: HIVE-8038.patch > > > What is the Current Logic > == > 1.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using the array index (index = > offset/blockSize), get the corresponding host having the blockLocation > 4.If the split spans multiple blocks, then get all hosts that have at least > 80% of the max of total data in split hosted by any host. > 5.add the split to a list of splits > Issue with Current Logic > = > Dependency on FileSystem API’s logic for block location calculations. It > returns an array and we need to rely on FileSystem to > make all blocks of same size if we want to directly access a block from the > array. > > What is the Fix > = > 1a.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 1b.convert the array into a tree map and return it > through getLocationsWithOffSet() > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using Tree.floorEntry(key), get the > highest entry smaller than offset for the split and get the corresponding > host. > 4a.If the split spans multiple blocks, get a submap, which contains all > entries containing blockLocations from the offset to offset + length > 4b.get all hosts that have at least 80% of the max of total data in split > hosted by any host. > 5.add the split to a list of splits > What are the major changes in logic > == > 1. store BlockLocations in a Map instead of an array > 2. Call SHIMS.getLocationsWithOffSet() instead of getLocations() > 3. one block case is checked by "if(offset + length <= start.getOffset() + > start.getLength())" instead of "if((offset % blockSize) + length <= > blockSize)" > What is the affect on Complexity (Big O) > = > 1. We add a O(n) loop to build a TreeMap from an array but its a one time > cost and would not be called for each split > 2. In case of one block case, we can get the block in O(logn) worst case > which was O(1) before > 3. Getting the submap is O(logn) > 4. In case of multiple block case, building the list of hosts is O(m) which > was O(n) & m < n as previously we were iterating >over all the block locations but now we are only iterating only blocks > that belong to that range go offsets that we need. > What are the benefits of the change > == > 1. With this fix, we do not depend on the blockLocations returned by > FileSystem to figure out the block corresponding to the offset and blockSize > 2. Also, it is not necessary that block lengths is same for all blocks for > all FileSystems > 3. Previously we were using blockSize for one block case and block.length for > multiple block case, which is not the case now. We figure out the block >depending upon the actual length and offset of the block -- This message was sent by Atlassian JIRA (v6.3.4#6332)
[jira] [Updated] (HIVE-8038) Decouple ORC files split calculation logic from Filesystem's get file location implementation
[ https://issues.apache.org/jira/browse/HIVE-8038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ] Pankit Thapar updated HIVE-8038: Attachment: HIVE-8038.patch > Decouple ORC files split calculation logic from Filesystem's get file > location implementation > - > > Key: HIVE-8038 > URL: https://issues.apache.org/jira/browse/HIVE-8038 > Project: Hive > Issue Type: Improvement > Components: File Formats >Affects Versions: 0.13.1 >Reporter: Pankit Thapar > Fix For: 0.14.0 > > Attachments: HIVE-8038.patch > > > What is the Current Logic > == > 1.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using the array index (index = > offset/blockSize), get the corresponding host having the blockLocation > 4.If the split spans multiple blocks, then get all hosts that have at least > 80% of the max of total data in split hosted by any host. > 5.add the split to a list of splits > Issue with Current Logic > = > Dependency on FileSystem API’s logic for block location calculations. It > returns an array and we need to rely on FileSystem to > make all blocks of same size if we want to directly access a block from the > array. > > What is the Fix > = > 1a.get the file blocks from FileSystem.getFileBlockLocations() which returns > an array of BlockLocation > 1b.convert the array into a tree map and return it > through getLocationsWithOffSet() > 2.In SplitGenerator.createSplit(), check if split only spans one block or > multiple blocks. > 3.If split spans just one block, then using Tree.floorEntry(key), get the > highest entry smaller than offset for the split and get the corresponding > host. > 4a.If the split spans multiple blocks, get a submap, which contains all > entries containing blockLocations from the offset to offset + length > 4b.get all hosts that have at least 80% of the max of total data in split > hosted by any host. > 5.add the split to a list of splits > What are the major changes in logic > == > 1. store BlockLocations in a Map instead of an array > 2. Call SHIMS.getLocationsWithOffSet() instead of getLocations() > 3. one block case is checked by "if(offset + length <= start.getOffset() + > start.getLength())" instead of "if((offset % blockSize) + length <= > blockSize)" > What is the affect on Complexity (Big O) > = > 1. We add a O(n) loop to build a TreeMap from an array but its a one time > cost and would not be called for each split > 2. In case of one block case, we can get the block in O(logn) worst case > which was O(1) before > 3. Getting the submap is O(logn) > 4. In case of multiple block case, building the list of hosts is O(m) which > was O(n) & m < n as previously we were iterating >over all the block locations but now we are only iterating only blocks > that belong to that range go offsets that we need. > What are the benefits of the change > == > 1. With this fix, we do not depend on the blockLocations returned by > FileSystem to figure out the block corresponding to the offset and blockSize > 2. Also, it is not necessary that block lengths is same for all blocks for > all FileSystems > 3. Previously we were using blockSize for one block case and block.length for > multiple block case, which is not the case now. We figure out the block >depending upon the actual length and offset of the block -- This message was sent by Atlassian JIRA (v6.3.4#6332)
