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Commit3fa81b6

Browse files
Fix btmarkpos/btrestrpos array key wraparound bug.
nbtree's mark/restore processing failed to correctly handle an edge caseinvolving array key advancement and related search-type scan key state.Scans with ScalarArrayScalarArrayOpExpr quals requiring mark/restoreprocessing (for a merge join) could incorrectly conclude that anaffected array/scan key must not have advanced during the time betweenmarking and restoring the scan's position.As a result of all this, array key handling within btrestrpos could skipa required call to _bt_preprocess_keys(). This confusion allowed laterprimitive index scans to overlook tuples matching the true current arraykeys. The scan's search-type scan keys would still have spurious valuescorresponding to the final array element(s) -- not values matching thefirst/now-current array element(s).To fix, remember that "array key wraparound" has taken place during theongoing btrescan in a flag variable stored in the scan's state, and usethat information at the point where btrestrpos decides if another callto _bt_preprocess_keys is required.Oversight in commit70bc583, which taught nbtree to handle array keysduring mark/restore processing, but missed this subtlety. That commitwas itself a bug fix for an issue in commit9e8da0f, which taughtnbtree to handle ScalarArrayOpExpr quals natively.Author: Peter Geoghegan <pg@bowt.ie>Discussion:https://postgr.es/m/CAH2-WzkgP3DDRJxw6DgjCxo-cu-DKrvjEv_ArkP2ctBJatDCYg@mail.gmail.comBackpatch: 11- (all supported branches).
1 parent12402b9 commit3fa81b6

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3 files changed

+20
-2
lines changed

3 files changed

+20
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‎src/backend/access/nbtree/nbtree.c

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Original file line numberDiff line numberDiff line change
@@ -364,6 +364,7 @@ btbeginscan(Relation rel, int nkeys, int norderbys)
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so->keyData=NULL;
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so->arrayKeyData=NULL;/* assume no array keys for now */
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so->arraysStarted= false;
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so->numArrayKeys=0;
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so->arrayKeys=NULL;
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so->arrayContext=NULL;

‎src/backend/access/nbtree/nbtutils.c

Lines changed: 16 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -539,6 +539,8 @@ _bt_start_array_keys(IndexScanDesc scan, ScanDirection dir)
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curArrayKey->cur_elem=0;
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skey->sk_argument=curArrayKey->elem_values[curArrayKey->cur_elem];
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}
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so->arraysStarted= true;
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}
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/*
@@ -598,6 +600,14 @@ _bt_advance_array_keys(IndexScanDesc scan, ScanDirection dir)
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if (scan->parallel_scan!=NULL)
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_bt_parallel_advance_array_keys(scan);
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/*
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* When no new array keys were found, the scan is "past the end" of the
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* array keys. _bt_start_array_keys can still "restart" the array keys if
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* a rescan is required.
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*/
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if (!found)
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so->arraysStarted= false;
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returnfound;
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}
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@@ -651,8 +661,13 @@ _bt_restore_array_keys(IndexScanDesc scan)
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* If we changed any keys, we must redo _bt_preprocess_keys. That might
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* sound like overkill, but in cases with multiple keys per index column
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* it seems necessary to do the full set of pushups.
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*
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* Also do this whenever the scan's set of array keys "wrapped around" at
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* the end of the last primitive index scan. There won't have been a call
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* to _bt_preprocess_keys from some other place following wrap around, so
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* we do it for ourselves.
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*/
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if (changed)
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if (changed|| !so->arraysStarted)
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{
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_bt_preprocess_keys(scan);
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/* The mark should have been set on a consistent set of keys... */

‎src/include/access/nbtree.h

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1036,8 +1036,10 @@ typedef struct BTArrayKeyInfo
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typedefstructBTScanOpaqueData
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{
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/*these fields are set by _bt_preprocess_keys(): */
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/*all fields (except arraysStarted) are set by _bt_preprocess_keys(): */
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boolqual_ok;/* false if qual can never be satisfied */
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boolarraysStarted;/* Started array keys, but have yet to "reach
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* past the end" of all arrays? */
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intnumberOfKeys;/* number of preprocessed scan keys */
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ScanKeykeyData;/* array of preprocessed scan keys */
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