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Commit398cf25

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In GIN recompression code, use mmemove rather than memcpy, for vacuum.
When vacuuming a data leaf page, any compressed posting lists that are notmodified, are copied back to the buffer from a later location in the samebuffer rather than from a palloc'd copy. IOW, they are just moveddownwards in the same buffer. Because the source and destination addressescan overlap, we must use memmove rather than memcpy.Report and fix by Alexander Korotkov.
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‎src/backend/access/gin/gindatapage.c‎

Lines changed: 14 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -753,6 +753,13 @@ ginVacuumPostingTreeLeaf(Relation indexrel, Buffer buffer, GinVacuumState *gvs)
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* *prdata is filled with WAL information about this operation. The caller
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* is responsible for inserting to the WAL, along with any other information
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* about the operation that triggered this recompression.
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*
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* NOTE: The segment pointers can point directly to the same buffer, with
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* the limitation that any earlier segment must not overlap with an original,
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* later segment. In other words, some segments may point the original buffer
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* as long as you don't make any segments larger. Currently, leafRepackItems
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* satisies this rule because it rewrites all segments after the first
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* modified one, and vacuum can only make segments shorter.
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*/
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staticvoid
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dataPlaceToPageLeafRecompress(Bufferbuf,disassembledLeaf*leaf,
@@ -798,7 +805,13 @@ dataPlaceToPageLeafRecompress(Buffer buf, disassembledLeaf *leaf,
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if (!modified)
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unmodifiedsize+=segsize;
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else
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memcpy(ptr,seginfo->seg,segsize);
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{
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/*
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* Use memmove rather than memcpy, in case the segment points
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* to the same buffer
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*/
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memmove(ptr,seginfo->seg,segsize);
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}
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ptr+=segsize;
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newsize+=segsize;
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}

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