Fix multiple bugs in contrib/pgstattuple's pgstatindex() function.

Dead or half-dead index leaf pages were incorrectly reported as live, as a
consequence of a code rearrangement I made (during a moment of severe brain
fade, evidently) in commit d287818eb514d431.

The index metapage was not counted in index_size, causing that result to
not agree with the actual index size on-disk.

Index root pages were not counted in internal_pages, which is inconsistent
compared to the case of a root that's also a leaf (one-page index), where
the root would be counted in leaf_pages.  Aside from that inconsistency,
this could lead to additional transient discrepancies between the reported
page counts and index_size, since it's possible for pgstatindex's scan to
see zero or multiple pages marked as BTP_ROOT, if the root moves due to
a split during the scan.  With these fixes, index_size will always be
exactly one page more than the sum of the displayed page counts.

Also, the index_size result was incorrectly documented as being measured in
pages; it's always been measured in bytes.  (While fixing that, I couldn't
resist doing some small additional wordsmithing on the pgstattuple docs.)

Including the metapage causes the reported index_size to not be zero for
an empty index.  To preserve the desired property that the pgstattuple
regression test results are platform-independent (ie, BLCKSZ configuration
independent), scale the index_size result in the regression tests.

The documentation issue was reported by Otsuka Kenji, and the inconsistent
root page counting by Peter Geoghegan; the other problems noted by me.
Back-patch to all supported branches, because this has been broken for
a long time.

diff --git a/contrib/pgstattuple/expected/pgstattuple.out b/contrib/pgstattuple/expected/pgstattuple.out
index d769f6d49431f9df7fcf25cbbb7e8a1e361c39ec..e920234488e1159bf8e9e442e8e77aab6d94b054 100644 (file)
--- a/contrib/pgstattuple/expected/pgstattuple.out
+++ b/contrib/pgstattuple/expected/pgstattuple.out
@@ -41,40 +41,44 @@ select pgstattuple(relname) from pg_class where relname = 'test';
  (0,0,0,0,0,0,0,0,0)
 (1 row)
 
-select * from pgstatindex('test_pkey');
+select version, tree_level,
+    index_size / current_setting('block_size')::int as index_size,
+    root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
+    avg_leaf_density, leaf_fragmentation
+    from pgstatindex('test_pkey');
  version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation 
 ---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
-       2 |          0 |          0 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
+       2 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
 (1 row)
 
-select * from pgstatindex('test_pkey'::text);
+select version, tree_level,
+    index_size / current_setting('block_size')::int as index_size,
+    root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
+    avg_leaf_density, leaf_fragmentation
+    from pgstatindex('test_pkey'::text);
  version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation 
 ---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
-       2 |          0 |          0 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
+       2 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
 (1 row)
 
-select * from pgstatindex('test_pkey'::name);
+select version, tree_level,
+    index_size / current_setting('block_size')::int as index_size,
+    root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
+    avg_leaf_density, leaf_fragmentation
+    from pgstatindex('test_pkey'::name);
  version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation 
 ---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
-       2 |          0 |          0 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
+       2 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
 (1 row)
 
-select * from pgstatindex('test_pkey'::regclass);
+select version, tree_level,
+    index_size / current_setting('block_size')::int as index_size,
+    root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
+    avg_leaf_density, leaf_fragmentation
+    from pgstatindex('test_pkey'::regclass);
  version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation 
 ---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
-       2 |          0 |          0 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
-(1 row)
-
-select pgstatindex(oid) from pg_class where relname = 'test_pkey';
-        pgstatindex        
----------------------------
- (2,0,0,0,0,0,0,0,NaN,NaN)
-(1 row)
-
-select pgstatindex(relname) from pg_class where relname = 'test_pkey';
-        pgstatindex        
----------------------------
- (2,0,0,0,0,0,0,0,NaN,NaN)
+       2 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
 (1 row)
 
 select pg_relpages('test');

diff --git a/contrib/pgstattuple/pgstatindex.c b/contrib/pgstattuple/pgstatindex.c
index 8048a2cbe7c3fa6dc889f8d829ee3cfb4726dfa9..9f1377c4cd943bf2348a2fee4b06b3419e73258b 100644 (file)
--- a/contrib/pgstattuple/pgstatindex.c
+++ b/contrib/pgstattuple/pgstatindex.c
@@ -79,7 +79,6 @@ typedef struct BTIndexStat
        uint32          level;
        BlockNumber root_blkno;
 
-       uint64          root_pages;
        uint64          internal_pages;
        uint64          leaf_pages;
        uint64          empty_pages;
@@ -185,7 +184,6 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
        }
 
        /* -- init counters -- */
-       indexStat.root_pages = 0;
        indexStat.internal_pages = 0;
        indexStat.leaf_pages = 0;
        indexStat.empty_pages = 0;
@@ -218,7 +216,11 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
 
                /* Determine page type, and update totals */
 
-               if (P_ISLEAF(opaque))
+               if (P_ISDELETED(opaque))
+                       indexStat.deleted_pages++;
+               else if (P_IGNORE(opaque))
+                       indexStat.empty_pages++;        /* this is the "half dead" state */
+               else if (P_ISLEAF(opaque))
                {
                        int                     max_avail;
 
@@ -235,12 +237,6 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
                        if (opaque->btpo_next != P_NONE && opaque->btpo_next < blkno)
                                indexStat.fragments++;
                }
-               else if (P_ISDELETED(opaque))
-                       indexStat.deleted_pages++;
-               else if (P_IGNORE(opaque))
-                       indexStat.empty_pages++;
-               else if (P_ISROOT(opaque))
-                       indexStat.root_pages++;
                else
                        indexStat.internal_pages++;
 
@@ -269,7 +265,7 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
                values[j++] = psprintf("%d", indexStat.version);
                values[j++] = psprintf("%d", indexStat.level);
                values[j++] = psprintf(INT64_FORMAT,
-                                                          (indexStat.root_pages +
+                                                          (1 +         /* include the metapage in index_size */
                                                                indexStat.leaf_pages +
                                                                indexStat.internal_pages +
                                                                indexStat.deleted_pages +

diff --git a/contrib/pgstattuple/sql/pgstattuple.sql b/contrib/pgstattuple/sql/pgstattuple.sql
index 0e0ad0e15d5a7b256c06d6208327d178a5f9d251..d22c9f1c46dc1432339feda59c4248378a4fc22e 100644 (file)
--- a/contrib/pgstattuple/sql/pgstattuple.sql
+++ b/contrib/pgstattuple/sql/pgstattuple.sql
@@ -15,12 +15,26 @@ select * from pgstattuple('test'::regclass);
 select pgstattuple(oid) from pg_class where relname = 'test';
 select pgstattuple(relname) from pg_class where relname = 'test';
 
-select * from pgstatindex('test_pkey');
-select * from pgstatindex('test_pkey'::text);
-select * from pgstatindex('test_pkey'::name);
-select * from pgstatindex('test_pkey'::regclass);
-select pgstatindex(oid) from pg_class where relname = 'test_pkey';
-select pgstatindex(relname) from pg_class where relname = 'test_pkey';
+select version, tree_level,
+    index_size / current_setting('block_size')::int as index_size,
+    root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
+    avg_leaf_density, leaf_fragmentation
+    from pgstatindex('test_pkey');
+select version, tree_level,
+    index_size / current_setting('block_size')::int as index_size,
+    root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
+    avg_leaf_density, leaf_fragmentation
+    from pgstatindex('test_pkey'::text);
+select version, tree_level,
+    index_size / current_setting('block_size')::int as index_size,
+    root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
+    avg_leaf_density, leaf_fragmentation
+    from pgstatindex('test_pkey'::name);
+select version, tree_level,
+    index_size / current_setting('block_size')::int as index_size,
+    root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
+    avg_leaf_density, leaf_fragmentation
+    from pgstatindex('test_pkey'::regclass);
 
 select pg_relpages('test');
 select pg_relpages('test_pkey');

diff --git a/doc/src/sgml/pgstattuple.sgml b/doc/src/sgml/pgstattuple.sgml
index 18d244ba3a3912631bfd23d212336195076d20fe..61340bedbc37866be92abc5558c4a7a7150dbb45 100644 (file)
--- a/doc/src/sgml/pgstattuple.sgml
+++ b/doc/src/sgml/pgstattuple.sgml
@@ -130,9 +130,9 @@ free_percent       | 1.95
     <listitem>
      <para>
       This is the same as <function>pgstattuple(regclass)</function>, except
-      that the target relation is specified by TEXT. This function is kept
+      that the target relation is specified as TEXT. This function is kept
       because of backward-compatibility so far, and will be deprecated in
-      the future release.
+      some future release.
      </para>
     </listitem>
    </varlistentry>
@@ -154,13 +154,13 @@ test=&gt; SELECT * FROM pgstatindex('pg_cast_oid_index');
 -[ RECORD 1 ]------+------
 version            | 2
 tree_level         | 0
-index_size         | 8192
+index_size         | 16384
 root_block_no      | 1
 internal_pages     | 0
 leaf_pages         | 1
 empty_pages        | 0
 deleted_pages      | 0
-avg_leaf_density   | 50.27
+avg_leaf_density   | 54.27
 leaf_fragmentation | 0
 </programlisting>
      </para>
@@ -194,13 +194,13 @@ leaf_fragmentation | 0
        <row>
         <entry><structfield>index_size</structfield></entry>
         <entry><type>bigint</type></entry>
-        <entry>Total number of pages in index</entry>
+        <entry>Total index size in bytes</entry>
        </row>
 
        <row>
         <entry><structfield>root_block_no</structfield></entry>
         <entry><type>bigint</type></entry>
-        <entry>Location of root block</entry>
+        <entry>Location of root page (zero if none)</entry>
        </row>
 
        <row>
@@ -244,6 +244,13 @@ leaf_fragmentation | 0
     </informaltable>
     </para>
 
+    <para>
+     The reported <literal>index_size</> will normally correspond to one more
+     page than is accounted for by <literal>internal_pages + leaf_pages +
+     empty_pages + deleted_pages</literal>, because it also includes the
+     index's metapage.
+    </para>
+
     <para>
      As with <function>pgstattuple</>, the results are accumulated
      page-by-page, and should not be expected to represent an
@@ -260,9 +267,9 @@ leaf_fragmentation | 0
     <listitem>
      <para>
       This is the same as <function>pgstatindex(regclass)</function>, except
-      that the target index is specified by TEXT. This function is kept
+      that the target index is specified as TEXT. This function is kept
       because of backward-compatibility so far, and will be deprecated in
-      the future release.
+      some future release.
      </para>
     </listitem>
    </varlistentry>
@@ -351,9 +358,9 @@ pending_tuples | 0
     <listitem>
      <para>
       This is the same as <function>pg_relpages(regclass)</function>, except
-      that the target relation is specified by TEXT. This function is kept
+      that the target relation is specified as TEXT. This function is kept
       because of backward-compatibility so far, and will be deprecated in
-      the future release.
+      some future release.
      </para>
     </listitem>
    </varlistentry>
@@ -370,7 +377,7 @@ pending_tuples | 0
      <para>
       <function>pgstattuple_approx</function> is a faster alternative to
       <function>pgstattuple</function> that returns approximate results.
-      The argument is the target relation's OID.
+      The argument is the target relation's name or OID.
       For example:
 <programlisting>
 test=&gt; SELECT * FROM pgstattuple_approx('pg_catalog.pg_proc'::regclass);