postgres.git / summary / log / commit / refs
commit b36d72cbc6b008da062ac84850254a9de0da93d4
Author: Peter Geoghegan <pg@bowt.ie>
Date: Thu Sep 28 23:29:24 2023 +0000
First released in: 17.0, 11.22, 12.17, 13.13, 14.10, 15.5, 16.1
Fix btmarkpos/btrestrpos array key wraparound bug.
nbtree's mark/restore processing failed to correctly handle an edge case
involving array key advancement and related search-type scan key state.
Scans with ScalarArrayScalarArrayOpExpr quals requiring mark/restore
processing (for a merge join) could incorrectly conclude that an
affected array/scan key must not have advanced during the time between
marking and restoring the scan's position.
As a result of all this, array key handling within btrestrpos could skip
a required call to _bt_preprocess_keys(). This confusion allowed later
primitive index scans to overlook tuples matching the true current array
keys. The scan's search-type scan keys would still have spurious values
corresponding to the final array element(s) -- not values matching the
first/now-current array element(s).
To fix, remember that "array key wraparound" has taken place during the
ongoing btrescan in a flag variable stored in the scan's state, and use
that information at the point where btrestrpos decides if another call
to _bt_preprocess_keys is required.
Oversight in commit 70bc5833, which taught nbtree to handle array keys
during mark/restore processing, but missed this subtlety. That commit
was itself a bug fix for an issue in commit 9e8da0f7, which taught
nbtree to handle ScalarArrayOpExpr quals natively.
Author: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAH2-WzkgP3DDRJxw6DgjCxo-cu-DKrvjEv_ArkP2ctBJatDCYg@mail.gmail.com
Backpatch: 11- (all supported branches).
src/backend/access/nbtree/nbtree.c | 1 +
src/backend/access/nbtree/nbtutils.c | 17 ++++++++++++++++-
src/include/access/nbtree.h | 4 +++-
3 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index c2e83d3ee5e..cfc0ad48fcd 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -366,6 +366,7 @@ btbeginscan(Relation rel, int nkeys, int norderbys)
so->keyData = NULL;
so->arrayKeyData = NULL; /* assume no array keys for now */
+ so->arraysStarted = false;
so->numArrayKeys = 0;
so->arrayKeys = NULL;
so->arrayContext = NULL;
diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c
index ff6d3330fa2..0e9cc574df4 100644
--- a/src/backend/access/nbtree/nbtutils.c
+++ b/src/backend/access/nbtree/nbtutils.c
@@ -534,6 +534,8 @@ _bt_start_array_keys(IndexScanDesc scan, ScanDirection dir)
curArrayKey->cur_elem = 0;
skey->sk_argument = curArrayKey->elem_values[curArrayKey->cur_elem];
}
+
+ so->arraysStarted = true;
}
/*
@@ -593,6 +595,14 @@ _bt_advance_array_keys(IndexScanDesc scan, ScanDirection dir)
if (scan->parallel_scan != NULL)
_bt_parallel_advance_array_keys(scan);
+ /*
+ * When no new array keys were found, the scan is "past the end" of the
+ * array keys. _bt_start_array_keys can still "restart" the array keys if
+ * a rescan is required.
+ */
+ if (!found)
+ so->arraysStarted = false;
+
return found;
}
@@ -646,8 +656,13 @@ _bt_restore_array_keys(IndexScanDesc scan)
* If we changed any keys, we must redo _bt_preprocess_keys. That might
* sound like overkill, but in cases with multiple keys per index column
* it seems necessary to do the full set of pushups.
+ *
+ * Also do this whenever the scan's set of array keys "wrapped around" at
+ * the end of the last primitive index scan. There won't have been a call
+ * to _bt_preprocess_keys from some other place following wrap around, so
+ * we do it for ourselves.
*/
- if (changed)
+ if (changed || !so->arraysStarted)
{
_bt_preprocess_keys(scan);
/* The mark should have been set on a consistent set of keys... */
diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index 8f81663e5c0..883c7dc3cfc 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -628,8 +628,10 @@ typedef struct BTArrayKeyInfo
typedef struct BTScanOpaqueData
{
- /* these fields are set by _bt_preprocess_keys(): */
+ /* all fields (except arraysStarted) are set by _bt_preprocess_keys(): */
bool qual_ok; /* false if qual can never be satisfied */
+ bool arraysStarted; /* Started array keys, but have yet to "reach
+ * past the end" of all arrays? */
int numberOfKeys; /* number of preprocessed scan keys */
ScanKey keyData; /* array of preprocessed scan keys */
[parent: d6425987ba76]