[DRILL-3285] Split DrillCursor.next(), clean up DrillCursor for clarity

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.1.0
• Component/s: Client - JDBC
• Assignee: Mehant Baid
• Reporter: Daniel Barclay
• Created: 12/Jun/15 19:01
• Updated: 23/Jun/15 19:01
• Resolved: 23/Jun/15 19:01

Description

Clean up the mess in DrillCursor, namely the poorly named (and of course undocumented) flow-control flags and the flag-laden next() method.

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DRILL-3285: Part 1--Prep., Hygiene: Mainly, adding comments.

Added/edited comments:

• field doc. comments
• method doc. comments
• branch/block comments

Removed unused recordBatchCount and getRecordBatchCount().

Added logger call for spurious batch.

Various cleanup:

• Cleaned up logger.
• Added "final" on updateColumns().
• Wrapped some lines
• Misc. comment whitespace.

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DRILL-3285: Part 2--Renaming.

Renamed state/control-flow members:

• started -> initialSchemaLoaded
• first -> beforeFirstBatch
• redoFirstNext -> returnTrueForNextCallToNext
• finished -> afterLastRow

Renamed other items:

• changed -> schemaChanged
• currentBatch -> currentBatchHolder
• DrillResultSet's currentBatch -> batchLoader

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DRILL-3285: Part 3--Invert beforeFirstBatch -> ! afterFirstBatch.

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DRILL-3285: Part 4--Reorder fields, updateColumns.

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DRILL-3285: Part 5--Split old hacky next() into separate methods.

Split the original public next() method (which was hacked to handle an extra,
initial call to read the schema batch) into:

• new loadInitialSchema() (for handling the call for the schema)
• modified next() (for handling normal calls from ResultSet.next())
• new private nextRowInternally() (for common code)

Pulls invariant afterFirstBatch up out of bogus-batch loop.

Issue Links

• is required by: DRILL-2560 JDBC execute calls return asynchronously for DDL statements