Author:     Noah Misch <noah@leadboat.com>
Commit:     Noah Misch <noah@leadboat.com>

    Dissociate btequalimage() from interval_ops, ending its deduplication.
    
    Under interval_ops, some equal values are distinguishable.  One such
    pair is '24:00:00' and '1 day'.  With that being so, btequalimage()
    breaches the documented contract for the "equalimage" btree support
    function.  This can cause incorrect results from index-only scans.
    Users should REINDEX any indexes having interval-type columns and for
    which "pg_amcheck --heapallindexed" reports an error.  This fix makes
    interval_ops simply omit the support function, like numeric_ops does.
    Back-pack to v13, where btequalimage() first appeared.  In back
    branches, for the benefit of old catalog content, btequalimage() code
    will return false for type "interval".  Going forward, back-branch
    initdb will include the catalog change.
    
    Reviewed by FIXME.
    
    Discussion: https://postgr.es/m/FIXME

diff --git a/src/backend/utils/adt/datum.c b/src/backend/utils/adt/datum.c
index 9f06ee7..251dd23 100644
--- a/src/backend/utils/adt/datum.c
+++ b/src/backend/utils/adt/datum.c
@@ -43,6 +43,7 @@
 #include "postgres.h"
 
 #include "access/detoast.h"
+#include "catalog/pg_type_d.h"
 #include "common/hashfn.h"
 #include "fmgr.h"
 #include "utils/builtins.h"
@@ -385,20 +386,17 @@ datum_image_hash(Datum value, bool typByVal, int typLen)
  * datum_image_eq() in all cases can use this as their "equalimage" support
  * function.
  *
- * Currently, we unconditionally assume that any B-Tree operator class that
- * registers btequalimage as its support function 4 must be able to safely use
- * optimizations like deduplication (i.e. we return true unconditionally).  If
- * it ever proved necessary to rescind support for an operator class, we could
- * do that in a targeted fashion by doing something with the opcintype
- * argument.
+ * Earlier minor releases erroneously associated this function with
+ * interval_ops.  Detect that case to rescind deduplication support, without
+ * requiring initdb.
  *-------------------------------------------------------------------------
  */
 Datum
 btequalimage(PG_FUNCTION_ARGS)
 {
-	/* Oid		opcintype = PG_GETARG_OID(0); */
+	Oid			opcintype = PG_GETARG_OID(0);
 
-	PG_RETURN_BOOL(true);
+	PG_RETURN_BOOL(opcintype != INTERVALOID);
 }
 
 /*-------------------------------------------------------------------------
diff --git a/src/include/catalog/pg_amproc.dat b/src/include/catalog/pg_amproc.dat
index 5b95012..4c70da4 100644
--- a/src/include/catalog/pg_amproc.dat
+++ b/src/include/catalog/pg_amproc.dat
@@ -172,8 +172,6 @@
 { amprocfamily => 'btree/interval_ops', amproclefttype => 'interval',
   amprocrighttype => 'interval', amprocnum => '3',
   amproc => 'in_range(interval,interval,interval,bool,bool)' },
-{ amprocfamily => 'btree/interval_ops', amproclefttype => 'interval',
-  amprocrighttype => 'interval', amprocnum => '4', amproc => 'btequalimage' },
 { amprocfamily => 'btree/macaddr_ops', amproclefttype => 'macaddr',
   amprocrighttype => 'macaddr', amprocnum => '1', amproc => 'macaddr_cmp' },
 { amprocfamily => 'btree/macaddr_ops', amproclefttype => 'macaddr',
diff --git a/src/test/regress/expected/opr_sanity.out b/src/test/regress/expected/opr_sanity.out
index a1bdf2c..7a6f36a 100644
--- a/src/test/regress/expected/opr_sanity.out
+++ b/src/test/regress/expected/opr_sanity.out
@@ -2208,6 +2208,7 @@ ORDER BY 1, 2, 3;
                     | array_ops        | array_ops        | anyarray
                     | float_ops        | float4_ops       | real
                     | float_ops        | float8_ops       | double precision
+                    | interval_ops     | interval_ops     | interval
                     | jsonb_ops        | jsonb_ops        | jsonb
                     | multirange_ops   | multirange_ops   | anymultirange
                     | numeric_ops      | numeric_ops      | numeric
@@ -2216,7 +2217,7 @@ ORDER BY 1, 2, 3;
                     | record_ops       | record_ops       | record
                     | tsquery_ops      | tsquery_ops      | tsquery
                     | tsvector_ops     | tsvector_ops     | tsvector
-(15 rows)
+(16 rows)
 
 -- **************** pg_index ****************
 -- Look for illegal values in pg_index fields.