Fix crash in BRIN inclusion op functions, due to missing datum copy.

The BRIN add_value() and union() functions need to make a longer-lived
copy of the argument, if they want to store it in the BrinValues struct
also passed as argument. The functions for the "inclusion operator
classes" used with box, range and inet types didn't take into account
that the union helper function might return its argument as is, without
making a copy. Check for that case, and make a copy if necessary. That
case arises at least with the range_union() function, when one of the
arguments is an 'empty' range:

CREATE TABLE brintest (n numrange);
CREATE INDEX brinidx ON brintest USING brin (n);
INSERT INTO brintest VALUES ('empty');
INSERT INTO brintest VALUES (numrange(0, 2^1000::numeric));
INSERT INTO brintest VALUES ('(-1, 0)');

SELECT brin_desummarize_range('brinidx', 0);
SELECT brin_summarize_range('brinidx', 0);

Backpatch down to 9.5, where BRIN was introduced.

Discussion: https://www.postgresql.org/message-id/e6e1d6eb-0a67-36aa-e779-bcca59167c14%40iki.fi
Reviewed-by: Emre Hasegeli, Tom Lane, Alvaro Herrera

diff --git a/src/backend/access/brin/brin_inclusion.c b/src/backend/access/brin/brin_inclusion.c
index 86788024ef658c5ee0948dae73c385d99e2fbfb2..9d7cb36a47a003a97405ef806987329be05f21e7 100644 (file)
--- a/src/backend/access/brin/brin_inclusion.c
+++ b/src/backend/access/brin/brin_inclusion.c
@@ -235,8 +235,14 @@ brin_inclusion_add_value(PG_FUNCTION_ARGS)
    Assert(finfo != NULL);
    result = FunctionCall2Coll(finfo, colloid,
                               column->bv_values[INCLUSION_UNION], newval);
-   if (!attr->attbyval)
+   if (!attr->attbyval &&
+       DatumGetPointer(result) != DatumGetPointer(column->bv_values[INCLUSION_UNION]))
+   {
        pfree(DatumGetPointer(column->bv_values[INCLUSION_UNION]));
+
+       if (result == newval)
+           result = datumCopy(result, attr->attbyval, attr->attlen);
+   }
    column->bv_values[INCLUSION_UNION] = result;
 
    PG_RETURN_BOOL(true);
@@ -574,8 +580,14 @@ brin_inclusion_union(PG_FUNCTION_ARGS)
    result = FunctionCall2Coll(finfo, colloid,
                               col_a->bv_values[INCLUSION_UNION],
                               col_b->bv_values[INCLUSION_UNION]);
-   if (!attr->attbyval)
+   if (!attr->attbyval &&
+       DatumGetPointer(result) != DatumGetPointer(col_a->bv_values[INCLUSION_UNION]))
+   {
        pfree(DatumGetPointer(col_a->bv_values[INCLUSION_UNION]));
+
+       if (result == col_b->bv_values[INCLUSION_UNION])
+           result = datumCopy(result, attr->attbyval, attr->attlen);
+   }
    col_a->bv_values[INCLUSION_UNION] = result;
 
    PG_RETURN_VOID();