/* ---------------- * index_getbitmap - get all tuples at once from an index scan * * Adds the TIDs of all heap tuples satisfying the scan keys to a bitmap. * Since there's no interlock between the index scan and the eventual heap * access, this is only safe to use with MVCC-based snapshots: the heap * item slot could have been replaced by a newer tuple by the time we get * to it. * * Returns the number of matching tuples found. (Note: this might be only * approximate, so it should only be used for statistical purposes.) * ---------------- */ int64 index_getbitmap(IndexScanDesc scan, TIDBitmap *bitmap) { FmgrInfo *procedure; int64 ntids; Datum d; SCAN_CHECKS; GET_SCAN_PROCEDURE(amgetbitmap); /* just make sure this is false... */ scan->kill_prior_tuple = false; /* * have the am's getbitmap proc do all the work. */ d = FunctionCall2(procedure, PointerGetDatum(scan), PointerGetDatum(bitmap)); ntids = DatumGetInt64(d); /* If int8 is pass-by-ref, must free the result to avoid memory leak */ #ifndef USE_FLOAT8_BYVAL pfree(DatumGetPointer(d)); #endif pgstat_count_index_tuples(scan->indexRelation, ntids); return ntids; }
/* ---------------- * index_getbitmap - get all tuples at once from an index scan * * Adds the TIDs of all heap tuples satisfying the scan keys to a bitmap. * Since there's no interlock between the index scan and the eventual heap * access, this is only safe to use with MVCC-based snapshots: the heap * item slot could have been replaced by a newer tuple by the time we get * to it. * * Returns the number of matching tuples found. (Note: this might be only * approximate, so it should only be used for statistical purposes.) * ---------------- */ int64 index_getbitmap(IndexScanDesc scan, TIDBitmap *bitmap) { int64 ntids; SCAN_CHECKS; CHECK_SCAN_PROCEDURE(amgetbitmap); /* just make sure this is false... */ scan->kill_prior_tuple = false; /* * have the am's getbitmap proc do all the work. */ ntids = scan->indexRelation->rd_amroutine->amgetbitmap(scan, bitmap); pgstat_count_index_tuples(scan->indexRelation, ntids); return ntids; }
/* ---------------- * index_getnext_tid - get the next TID from a scan * * The result is the next TID satisfying the scan keys, * or NULL if no more matching tuples exist. * ---------------- */ ItemPointer index_getnext_tid(IndexScanDesc scan, ScanDirection direction) { FmgrInfo *procedure; bool found; SCAN_CHECKS; GET_SCAN_PROCEDURE(amgettuple); Assert(TransactionIdIsValid(RecentGlobalXmin)); /* * The AM's amgettuple proc finds the next index entry matching the scan * keys, and puts the TID into scan->xs_ctup.t_self. It should also set * scan->xs_recheck and possibly scan->xs_itup, though we pay no attention * to those fields here. */ found = DatumGetBool(FunctionCall2(procedure, PointerGetDatum(scan), Int32GetDatum(direction))); /* Reset kill flag immediately for safety */ scan->kill_prior_tuple = false; /* If we're out of index entries, we're done */ if (!found) { /* ... but first, release any held pin on a heap page */ if (BufferIsValid(scan->xs_cbuf)) { ReleaseBuffer(scan->xs_cbuf); scan->xs_cbuf = InvalidBuffer; } return NULL; } pgstat_count_index_tuples(scan->indexRelation, 1); /* Return the TID of the tuple we found. */ return &scan->xs_ctup.t_self; }
/* ---------------- * index_getnext_indexitem - get the next index tuple from a scan * * Finds the next index tuple satisfying the scan keys. Note that the * corresponding heap tuple is not accessed, and thus no time qual (snapshot) * check is done, other than the index AM's internal check for killed tuples * (which most callers of this routine will probably want to suppress by * setting scan->ignore_killed_tuples = false). * * On success (TRUE return), the heap TID of the found index entry is in * scan->xs_ctup.t_self. scan->xs_cbuf is untouched. * ---------------- */ bool index_getnext_indexitem(IndexScanDesc scan, ScanDirection direction) { FmgrInfo *procedure; bool found; SCAN_CHECKS; GET_SCAN_PROCEDURE(amgettuple); /* just make sure this is false... */ scan->kill_prior_tuple = false; /* * have the am's gettuple proc do all the work. */ found = DatumGetBool(FunctionCall2(procedure, PointerGetDatum(scan), Int32GetDatum(direction))); pgstat_count_index_tuples(scan->indexRelation, 1 /*ntids*/); return found; }
/* ---------------- * index_getnext - get the next heap tuple from a scan * * The result is the next heap tuple satisfying the scan keys and the * snapshot, or NULL if no more matching tuples exist. On success, * the buffer containing the heap tuple is pinned (the pin will be dropped * at the next index_getnext or index_endscan). * * Note: caller must check scan->xs_recheck, and perform rechecking of the * scan keys if required. We do not do that here because we don't have * enough information to do it efficiently in the general case. * ---------------- */ HeapTuple index_getnext(IndexScanDesc scan, ScanDirection direction) { HeapTuple heapTuple = &scan->xs_ctup; ItemPointer tid = &heapTuple->t_self; FmgrInfo *procedure; SCAN_CHECKS; GET_SCAN_PROCEDURE(amgettuple); Assert(TransactionIdIsValid(RecentGlobalXmin)); /* * We always reset xs_hot_dead; if we are here then either we are just * starting the scan, or we previously returned a visible tuple, and in * either case it's inappropriate to kill the prior index entry. */ scan->xs_hot_dead = false; for (;;) { OffsetNumber offnum; bool at_chain_start; Page dp; if (scan->xs_next_hot != InvalidOffsetNumber) { /* * We are resuming scan of a HOT chain after having returned an * earlier member. Must still hold pin on current heap page. */ Assert(BufferIsValid(scan->xs_cbuf)); Assert(ItemPointerGetBlockNumber(tid) == BufferGetBlockNumber(scan->xs_cbuf)); Assert(TransactionIdIsValid(scan->xs_prev_xmax)); offnum = scan->xs_next_hot; at_chain_start = false; scan->xs_next_hot = InvalidOffsetNumber; } else { bool found; Buffer prev_buf; /* * If we scanned a whole HOT chain and found only dead tuples, * tell index AM to kill its entry for that TID. We do not do this * when in recovery because it may violate MVCC to do so. see * comments in RelationGetIndexScan(). */ if (!scan->xactStartedInRecovery) scan->kill_prior_tuple = scan->xs_hot_dead; /* * The AM's gettuple proc finds the next index entry matching the * scan keys, and puts the TID in xs_ctup.t_self (ie, *tid). It * should also set scan->xs_recheck, though we pay no attention to * that here. */ found = DatumGetBool(FunctionCall2(procedure, PointerGetDatum(scan), Int32GetDatum(direction))); /* Reset kill flag immediately for safety */ scan->kill_prior_tuple = false; /* If we're out of index entries, break out of outer loop */ if (!found) break; pgstat_count_index_tuples(scan->indexRelation, 1); /* Switch to correct buffer if we don't have it already */ prev_buf = scan->xs_cbuf; scan->xs_cbuf = ReleaseAndReadBuffer(scan->xs_cbuf, scan->heapRelation, ItemPointerGetBlockNumber(tid)); /* * Prune page, but only if we weren't already on this page */ if (prev_buf != scan->xs_cbuf) heap_page_prune_opt(scan->heapRelation, scan->xs_cbuf, RecentGlobalXmin); /* Prepare to scan HOT chain starting at index-referenced offnum */ offnum = ItemPointerGetOffsetNumber(tid); at_chain_start = true; /* We don't know what the first tuple's xmin should be */ scan->xs_prev_xmax = InvalidTransactionId; /* Initialize flag to detect if all entries are dead */ scan->xs_hot_dead = true; } /* Obtain share-lock on the buffer so we can examine visibility */ LockBuffer(scan->xs_cbuf, BUFFER_LOCK_SHARE); dp = (Page) BufferGetPage(scan->xs_cbuf); /* Scan through possible multiple members of HOT-chain */ for (;;) { ItemId lp; ItemPointer ctid; bool valid; /* check for bogus TID */ if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(dp)) break; lp = PageGetItemId(dp, offnum); /* check for unused, dead, or redirected items */ if (!ItemIdIsNormal(lp)) { /* We should only see a redirect at start of chain */ if (ItemIdIsRedirected(lp) && at_chain_start) { /* Follow the redirect */ offnum = ItemIdGetRedirect(lp); at_chain_start = false; continue; } /* else must be end of chain */ break; } /* * We must initialize all of *heapTuple (ie, scan->xs_ctup) since * it is returned to the executor on success. */ heapTuple->t_data = (HeapTupleHeader) PageGetItem(dp, lp); heapTuple->t_len = ItemIdGetLength(lp); ItemPointerSetOffsetNumber(tid, offnum); heapTuple->t_tableOid = RelationGetRelid(scan->heapRelation); ctid = &heapTuple->t_data->t_ctid; /* * Shouldn't see a HEAP_ONLY tuple at chain start. (This test * should be unnecessary, since the chain root can't be removed * while we have pin on the index entry, but let's make it * anyway.) */ if (at_chain_start && HeapTupleIsHeapOnly(heapTuple)) break; /* * The xmin should match the previous xmax value, else chain is * broken. (Note: this test is not optional because it protects * us against the case where the prior chain member's xmax aborted * since we looked at it.) */ if (TransactionIdIsValid(scan->xs_prev_xmax) && !TransactionIdEquals(scan->xs_prev_xmax, HeapTupleHeaderGetXmin(heapTuple->t_data))) break; /* If it's visible per the snapshot, we must return it */ valid = HeapTupleSatisfiesVisibility(heapTuple, scan->xs_snapshot, scan->xs_cbuf); CheckForSerializableConflictOut(valid, scan->heapRelation, heapTuple, scan->xs_cbuf); if (valid) { /* * If the snapshot is MVCC, we know that it could accept at * most one member of the HOT chain, so we can skip examining * any more members. Otherwise, check for continuation of the * HOT-chain, and set state for next time. */ if (IsMVCCSnapshot(scan->xs_snapshot) && !IsolationIsSerializable()) scan->xs_next_hot = InvalidOffsetNumber; else if (HeapTupleIsHotUpdated(heapTuple)) { Assert(ItemPointerGetBlockNumber(ctid) == ItemPointerGetBlockNumber(tid)); scan->xs_next_hot = ItemPointerGetOffsetNumber(ctid); scan->xs_prev_xmax = HeapTupleHeaderGetXmax(heapTuple->t_data); } else scan->xs_next_hot = InvalidOffsetNumber; PredicateLockTuple(scan->heapRelation, heapTuple); LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK); pgstat_count_heap_fetch(scan->indexRelation); return heapTuple; } /* * If we can't see it, maybe no one else can either. Check to see * if the tuple is dead to all transactions. If we find that all * the tuples in the HOT chain are dead, we'll signal the index AM * to not return that TID on future indexscans. */ if (scan->xs_hot_dead && HeapTupleSatisfiesVacuum(heapTuple->t_data, RecentGlobalXmin, scan->xs_cbuf) != HEAPTUPLE_DEAD) scan->xs_hot_dead = false; /* * Check to see if HOT chain continues past this tuple; if so * fetch the next offnum (we don't bother storing it into * xs_next_hot, but must store xs_prev_xmax), and loop around. */ if (HeapTupleIsHotUpdated(heapTuple)) { Assert(ItemPointerGetBlockNumber(ctid) == ItemPointerGetBlockNumber(tid)); offnum = ItemPointerGetOffsetNumber(ctid); at_chain_start = false; scan->xs_prev_xmax = HeapTupleHeaderGetXmax(heapTuple->t_data); } else break; /* end of chain */ } /* loop over a single HOT chain */ LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK); /* Loop around to ask index AM for another TID */ scan->xs_next_hot = InvalidOffsetNumber; } /* Release any held pin on a heap page */ if (BufferIsValid(scan->xs_cbuf)) { ReleaseBuffer(scan->xs_cbuf); scan->xs_cbuf = InvalidBuffer; } return NULL; /* failure exit */ }
/* ---------------- * index_getnext - get the next heap tuple from a scan * * The result is the next heap tuple satisfying the scan keys and the * snapshot, or NULL if no more matching tuples exist. On success, * the buffer containing the heap tuple is pinned (the pin will be dropped * at the next index_getnext or index_endscan). * * Note: caller must check scan->xs_recheck, and perform rechecking of the * scan keys if required. We do not do that here because we don't have * enough information to do it efficiently in the general case. * ---------------- */ HeapTuple index_getnext(IndexScanDesc scan, ScanDirection direction) { HeapTuple heapTuple = &scan->xs_ctup; ItemPointer tid = &heapTuple->t_self; FmgrInfo *procedure; bool all_dead = false; SCAN_CHECKS; GET_SCAN_PROCEDURE(amgettuple); Assert(TransactionIdIsValid(RecentGlobalXmin)); for (;;) { bool got_heap_tuple; if (scan->xs_continue_hot) { /* * We are resuming scan of a HOT chain after having returned an * earlier member. Must still hold pin on current heap page. */ Assert(BufferIsValid(scan->xs_cbuf)); Assert(ItemPointerGetBlockNumber(tid) == BufferGetBlockNumber(scan->xs_cbuf)); } else { bool found; Buffer prev_buf; /* * If we scanned a whole HOT chain and found only dead tuples, * tell index AM to kill its entry for that TID. We do not do this * when in recovery because it may violate MVCC to do so. see * comments in RelationGetIndexScan(). */ if (!scan->xactStartedInRecovery) scan->kill_prior_tuple = all_dead; /* * The AM's gettuple proc finds the next index entry matching the * scan keys, and puts the TID in xs_ctup.t_self (ie, *tid). It * should also set scan->xs_recheck, though we pay no attention to * that here. */ found = DatumGetBool(FunctionCall2(procedure, PointerGetDatum(scan), Int32GetDatum(direction))); /* Reset kill flag immediately for safety */ scan->kill_prior_tuple = false; /* If we're out of index entries, break out of outer loop */ if (!found) break; pgstat_count_index_tuples(scan->indexRelation, 1); /* Switch to correct buffer if we don't have it already */ prev_buf = scan->xs_cbuf; scan->xs_cbuf = ReleaseAndReadBuffer(scan->xs_cbuf, scan->heapRelation, ItemPointerGetBlockNumber(tid)); /* * Prune page, but only if we weren't already on this page */ if (prev_buf != scan->xs_cbuf) heap_page_prune_opt(scan->heapRelation, scan->xs_cbuf, RecentGlobalXmin); } /* Obtain share-lock on the buffer so we can examine visibility */ LockBuffer(scan->xs_cbuf, BUFFER_LOCK_SHARE); got_heap_tuple = heap_hot_search_buffer(tid, scan->heapRelation, scan->xs_cbuf, scan->xs_snapshot, &scan->xs_ctup, &all_dead, !scan->xs_continue_hot); LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK); if (got_heap_tuple) { /* * Only in a non-MVCC snapshot can more than one member of the * HOT chain be visible. */ scan->xs_continue_hot = !IsMVCCSnapshot(scan->xs_snapshot); pgstat_count_heap_fetch(scan->indexRelation); return heapTuple; } /* Loop around to ask index AM for another TID */ scan->xs_continue_hot = false; } /* Release any held pin on a heap page */ if (BufferIsValid(scan->xs_cbuf)) { ReleaseBuffer(scan->xs_cbuf); scan->xs_cbuf = InvalidBuffer; } return NULL; /* failure exit */ }
/* ---------------- * index_getnext - get the next heap tuple from a scan * * The result is the next heap tuple satisfying the scan keys and the * snapshot, or NULL if no more matching tuples exist. On success, * the buffer containing the heap tuple is pinned (the pin will be dropped * at the next index_getnext or index_endscan). * ---------------- */ HeapTuple index_getnext(IndexScanDesc scan, ScanDirection direction) { MIRROREDLOCK_BUFMGR_DECLARE; HeapTuple heapTuple = &scan->xs_ctup; FmgrInfo *procedure; SCAN_CHECKS; GET_SCAN_PROCEDURE(amgettuple); /* just make sure this is false... */ scan->kill_prior_tuple = false; for (;;) { bool found; /* * The AM's gettuple proc finds the next tuple matching the scan keys. */ found = DatumGetBool(FunctionCall2(procedure, PointerGetDatum(scan), Int32GetDatum(direction))); /* Reset kill flag immediately for safety */ scan->kill_prior_tuple = false; if (!found) { /* Release any held pin on a heap page */ if (BufferIsValid(scan->xs_cbuf)) { ReleaseBuffer(scan->xs_cbuf); scan->xs_cbuf = InvalidBuffer; } return NULL; /* failure exit */ } pgstat_count_index_tuples(scan->indexRelation, 1); /* * Fetch the heap tuple and see if it matches the snapshot. */ if (heap_release_fetch(scan->heapRelation, scan->xs_snapshot, heapTuple, &scan->xs_cbuf, true, scan->indexRelation)) break; /* Skip if no undeleted tuple at this location */ if (heapTuple->t_data == NULL) continue; /* * If we can't see it, maybe no one else can either. Check to see if * the tuple is dead to all transactions. If so, signal the index AM * to not return it on future indexscans. * * We told heap_release_fetch to keep a pin on the buffer, so we can * re-access the tuple here. But we must re-lock the buffer first. */ // -------- MirroredLock ---------- MIRROREDLOCK_BUFMGR_LOCK; LockBuffer(scan->xs_cbuf, BUFFER_LOCK_SHARE); if (HeapTupleSatisfiesVacuum(heapTuple->t_data, RecentGlobalXmin, scan->xs_cbuf, true) == HEAPTUPLE_DEAD) scan->kill_prior_tuple = true; LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK); MIRROREDLOCK_BUFMGR_UNLOCK; // -------- MirroredLock ---------- } /* Success exit */ return heapTuple; }