Function fetchFromCurrentBlock

src/backend/access/appendonly/appendonlyam.c:2168–2226

* Fetch the tuple from the block indicated by the block directory entry that * covers the tuple. */

 * covers the tuple.
 */
static void
fetchFromCurrentBlock(AppendOnlyFetchDesc aoFetchDesc,
					  int64 rowNum,
					  TupleTableSlot *slot)
{
	bool							fetched;
	AOFetchBlockMetadata 			*currentBlock = &aoFetchDesc->currentBlock;
	AppendOnlyExecutorReadBlock 	*executorReadBlock = &aoFetchDesc->executorReadBlock;
	AppendOnlyBlockDirectoryEntry 	*entry = &currentBlock->blockDirectoryEntry;

	if (!currentBlock->gotContents)
	{
		/*
		 * Do decompression if necessary and get contents.
		 */
		AppendOnlyExecutorReadBlock_GetContents(executorReadBlock);

		currentBlock->gotContents = true;
	}

	fetched = AppendOnlyExecutorReadBlock_FetchTuple(executorReadBlock,
													 rowNum,
													 /* nkeys */ 0,
													 /* key */ NULL,
													 slot);
	if (!fetched)
	{
		if (AppendOnlyBlockDirectoryEntry_RangeHasRow(entry, rowNum))
		{
			/*
			 * We fell into a hole inside the resolved block directory entry
			 * we obtained from AppendOnlyBlockDirectory_GetEntry().
			 * This should not be happening for versions >= CB2. Scream
			 * appropriately. See AppendOnlyBlockDirectoryEntry for details.
			 */
			ereportif(AORelationVersion_Get(aoFetchDesc->relation) >= AORelationVersion_CB2,
					  ERROR,
					  (errcode(ERRCODE_INTERNAL_ERROR),
						  errmsg("tuple with row number %ld not found in block directory entry range", rowNum),
						  errdetail("block directory entry: (fileOffset = %ld, firstRowNum = %ld, "
									"afterFileOffset = %ld, lastRowNum = %ld)",
									entry->range.fileOffset,
									entry->range.firstRowNum,
									entry->range.afterFileOffset,
									entry->range.lastRowNum)));
		}
		else
		{
			/*
			 * The resolved block directory entry we obtained from
			 * AppendOnlyBlockDirectory_GetEntry() has range s.t.
			 * firstRowNum < lastRowNum < rowNum
			 * This can happen when rowNum maps to an aborted transaction, and
			 * we find an earlier committed block directory row due to the
			 * <= scan condition in AppendOnlyBlockDirectory_GetEntry().
			 */
		}
	}