Fix GIN's shimTriConsistentFn to not corrupt its input.

Commit 0f21db36d made an assumption that GIN triConsistentFns
would not modify their input entryRes[] arrays.  But in fact,
the "shim" triConsistentFn that we use for opclasses that don't
supply their own did exactly that, potentially leading to wrong
answers from a GIN index search.  Through bad luck, none of the
test cases that we have for such opclasses exposed the bug.

One response to this could be that the assumption of consistency check
functions not modifying entryRes[] arrays is a bad one, but it still
seems reasonable to me.  Notably, shimTriConsistentFn is itself
assuming that with respect to the underlying boolean consistentFn,
so it's sure being self-centered in supposing that it gets to do so.

Fortunately, it's quite simple to fix shimTriConsistentFn to restore
the entry-time state of entryRes[], so let's do that instead.

This issue doesn't affect any core GIN opclasses, since they all
supply their own triConsistentFns.  It does affect contrib modules
btree_gin, hstore, and intarray.

Along the way, I (tgl) noticed that shimTriConsistentFn failed to
pick up on a "recheck" flag returned by its first call to the boolean
consistentFn.  This may be only a latent problem, since it would be
unlikely for a consistentFn to set recheck for the all-false case
and not any other cases.  (Indeed, none of our contrib modules do
that.)  Nonetheless, it's formally wrong.

Reported-by: Vinod Sridharan <vsridh90@gmail.com>
Author: Vinod Sridharan <vsridh90@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAFMdLD7XzsXfi1+DpTqTgrD8XU0i2C99KuF=5VHLWjx4C1pkcg@mail.gmail.com
Backpatch-through: 13

diff --git a/contrib/intarray/expected/_int.out b/contrib/intarray/expected/_int.out
index 09ab23483f7bd81df96306a8e9710b4d6b0f9ef9..64d8878763283e0d75ba81425d3f779b962b1128 100644 (file)
--- a/contrib/intarray/expected/_int.out
+++ b/contrib/intarray/expected/_int.out
@@ -473,6 +473,12 @@ SELECT count(*) from test__int WHERE a @@ '!20 & !21';
   6344
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
+ count 
+-------
+    12
+(1 row)
+
 SET enable_seqscan = off;  -- not all of these would use index by default
 CREATE INDEX text_idx on test__int using gist ( a gist__int_ops );
 SELECT count(*) from test__int WHERE a && '{23,50}';
@@ -547,6 +553,12 @@ SELECT count(*) from test__int WHERE a @@ '!20 & !21';
   6344
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
+ count 
+-------
+    12
+(1 row)
+
 INSERT INTO test__int SELECT array(SELECT x FROM generate_series(1, 1001) x); -- should fail
 ERROR:  input array is too big (199 maximum allowed, 1001 current), use gist__intbig_ops opclass instead
 DROP INDEX text_idx;
@@ -629,6 +641,12 @@ SELECT count(*) from test__int WHERE a @@ '!20 & !21';
   6344
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
+ count 
+-------
+    12
+(1 row)
+
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gist (a gist__intbig_ops(siglen = 0));
 ERROR:  value 0 out of bounds for option "siglen"
@@ -709,6 +727,12 @@ SELECT count(*) from test__int WHERE a @@ '!20 & !21';
   6344
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
+ count 
+-------
+    12
+(1 row)
+
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gist ( a gist__intbig_ops );
 SELECT count(*) from test__int WHERE a && '{23,50}';
@@ -783,6 +807,12 @@ SELECT count(*) from test__int WHERE a @@ '!20 & !21';
   6344
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
+ count 
+-------
+    12
+(1 row)
+
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gin ( a gin__int_ops );
 SELECT count(*) from test__int WHERE a && '{23,50}';
@@ -857,6 +887,12 @@ SELECT count(*) from test__int WHERE a @@ '!20 & !21';
   6344
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
+ count 
+-------
+    12
+(1 row)
+
 DROP INDEX text_idx;
 -- Repeat the same queries with an extended data set. The data set is the
 -- same that we used before, except that each element in the array is
@@ -949,4 +985,10 @@ SELECT count(*) from more__int WHERE a @@ '!20 & !21';
   6344
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
+ count 
+-------
+    12
+(1 row)
+
 RESET enable_seqscan;

diff --git a/contrib/intarray/sql/_int.sql b/contrib/intarray/sql/_int.sql
index 95eec96c14e811ef25e81a1fb65aaa9fdef46381..ba4c298151a1ca0f68ac503c633d4597cc3fd22c 100644 (file)
--- a/contrib/intarray/sql/_int.sql
+++ b/contrib/intarray/sql/_int.sql
@@ -92,6 +92,7 @@ SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
 SELECT count(*) from test__int WHERE a @@ '20 | !21';
 SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
 
 SET enable_seqscan = off;  -- not all of these would use index by default
 
@@ -109,6 +110,7 @@ SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
 SELECT count(*) from test__int WHERE a @@ '20 | !21';
 SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
 
 INSERT INTO test__int SELECT array(SELECT x FROM generate_series(1, 1001) x); -- should fail
 
@@ -129,6 +131,7 @@ SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
 SELECT count(*) from test__int WHERE a @@ '20 | !21';
 SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
 
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gist (a gist__intbig_ops(siglen = 0));
@@ -147,6 +150,7 @@ SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
 SELECT count(*) from test__int WHERE a @@ '20 | !21';
 SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
 
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gist ( a gist__intbig_ops );
@@ -163,6 +167,7 @@ SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
 SELECT count(*) from test__int WHERE a @@ '20 | !21';
 SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
 
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gin ( a gin__int_ops );
@@ -179,6 +184,7 @@ SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
 SELECT count(*) from test__int WHERE a @@ '20 | !21';
 SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
 
 DROP INDEX text_idx;
 
@@ -214,6 +220,7 @@ SELECT count(*) from more__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from more__int WHERE a @@ '(20&23)|(50&68)';
 SELECT count(*) from more__int WHERE a @@ '20 | !21';
 SELECT count(*) from more__int WHERE a @@ '!20 & !21';
+SELECT count(*) from test__int WHERE a @@ '!2733 & (2738 | 254)';
 
 
 RESET enable_seqscan;

diff --git a/src/backend/access/gin/ginlogic.c b/src/backend/access/gin/ginlogic.c
index c38c27fbae2c2775706e3842ee1efa33a819b396..4fe7f55ab1314b058e92a9020c0807632633d65c 100644 (file)
--- a/src/backend/access/gin/ginlogic.c
+++ b/src/backend/access/gin/ginlogic.c
@@ -146,7 +146,9 @@ shimBoolConsistentFn(GinScanKey key)
  * every combination is O(n^2), so this is only feasible for a small number of
  * MAYBE inputs.
  *
- * NB: This function modifies the key->entryRes array!
+ * NB: This function modifies the key->entryRes array.  For now that's okay
+ * so long as we restore the entry-time contents before returning.  This may
+ * need revisiting if we ever invent multithreaded GIN scans, though.
  */
 static GinTernaryValue
 shimTriConsistentFn(GinScanKey key)
@@ -155,7 +157,7 @@ shimTriConsistentFn(GinScanKey key)
    int         maybeEntries[MAX_MAYBE_ENTRIES];
    int         i;
    bool        boolResult;
-   bool        recheck = false;
+   bool        recheck;
    GinTernaryValue curResult;
 
    /*
@@ -175,8 +177,8 @@ shimTriConsistentFn(GinScanKey key)
    }
 
    /*
-    * If none of the inputs were MAYBE, so we can just call consistent
-    * function as is.
+    * If none of the inputs were MAYBE, we can just call the consistent
+    * function as-is.
     */
    if (nmaybe == 0)
        return directBoolConsistentFn(key);
@@ -185,6 +187,7 @@ shimTriConsistentFn(GinScanKey key)
    for (i = 0; i < nmaybe; i++)
        key->entryRes[maybeEntries[i]] = GIN_FALSE;
    curResult = directBoolConsistentFn(key);
+   recheck = key->recheckCurItem;
 
    for (;;)
    {
@@ -206,13 +209,20 @@ shimTriConsistentFn(GinScanKey key)
        recheck |= key->recheckCurItem;
 
        if (curResult != boolResult)
-           return GIN_MAYBE;
+       {
+           curResult = GIN_MAYBE;
+           break;
+       }
    }
 
    /* TRUE with recheck is taken to mean MAYBE */
    if (curResult == GIN_TRUE && recheck)
        curResult = GIN_MAYBE;
 
+   /* We must restore the original state of the entryRes array */
+   for (i = 0; i < nmaybe; i++)
+       key->entryRes[maybeEntries[i]] = GIN_MAYBE;
+
    return curResult;
 }