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Commit8021985

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logtape.c: allocate read buffer even for an empty tape.
Prior to this commit, the read buffer was allocated at the time the tapewas rewound; but as an optimization, would not be allocated at all ifthe tape was empty.That optimization meant that it was valid to have a rewound tape withthe buffer set to NULL, but only if a number of conditions were metand only if the API was used properly. After7fdd919 refactored thecode to support lazily-allocating the buffer, Coverity startedcomplaining.The optimization for empty tapes doesn't seem important, so justallocate the buffer whether the tape has any data or not.Discussion:https://postgr.es/m/20351.1581868306%40sss.pgh.pa.us
1 parent0074919 commit8021985

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lines changed

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‎src/backend/utils/sort/logtape.c

Lines changed: 5 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -544,11 +544,8 @@ ltsConcatWorkerTapes(LogicalTapeSet *lts, TapeShare *shared,
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staticvoid
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ltsInitReadBuffer(LogicalTapeSet*lts,LogicalTape*lt)
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{
547-
if (lt->firstBlockNumber!=-1L)
548-
{
549-
Assert(lt->buffer_size>0);
550-
lt->buffer=palloc(lt->buffer_size);
551-
}
547+
Assert(lt->buffer_size>0);
548+
lt->buffer=palloc(lt->buffer_size);
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/* Read the first block, or reset if tape is empty */
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lt->nextBlockNumber=lt->firstBlockNumber;
@@ -839,13 +836,10 @@ LogicalTapeRewindForRead(LogicalTapeSet *lts, int tapenum, size_t buffer_size)
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/* Allocate a read buffer (unless the tape is empty) */
840837
if (lt->buffer)
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pfree(lt->buffer);
839+
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/* the buffer is lazily allocated, but set the size here */
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lt->buffer=NULL;
843-
lt->buffer_size=0;
844-
if (lt->firstBlockNumber!=-1L)
845-
{
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/* the buffer is lazily allocated, but set the size here */
847-
lt->buffer_size=buffer_size;
848-
}
842+
lt->buffer_size=buffer_size;
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}
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/*

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