supplied, it is expected that the
       <function>picksplit</function> function will classify them into more than
       one node; otherwise it is not possible to split the leaf tuples
       across multiple pages, which is the ultimate purpose of this
       operation.  Therefore, if the <function>picksplit</function> function
       ends up placing all the leaf tuples in the same node, the core
       SP-GiST code will override that decision and generate an inner
       tuple in which the leaf tuples are assigned at random to several
       identically-labeled nodes.  Such a tuple is marked
       <literal>allTheSame</literal> to signify that this has happened.  The
       <function>choose</function> and <function>inner_consistent</function> functions
       must take suitable care with such inner tuples.
       See <xref linkend="spgist-all-the-same"/> for more information.
      </para>

      <para>
       <function>picksplit</function> can be applied to a single leaf tuple only
       in the case that the <function>config</function> function set
       <structfield>longValuesOK</structfield> to true and a larger-than-a-page input
       value has been supplied.  In this case the point of the operation is
       to strip off a prefix and produce a new, shorter leaf datum value.
       The call will be repeated until a leaf datum short enough to fit on
       a page has been produced.  See <xref linkend="spgist-limits"/> for
       more information.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><function>inner_consistent</function></term>
     <listitem>
      <para>
       Returns set of nodes (branches) to follow during tree search.
      </para>

      <para>
       The <acronym>SQL</acronym> declaration of the function must look like this:
<programlisting>
CREATE FUNCTION my_inner_consistent(internal, internal) RETURNS void ...
</programlisting>
      The first argument is a pointer to a <structname>spgInnerConsistentIn</structname>
      C struct, containing input data for the function.
      The second argument is a pointer to a <structname>spgInnerConsistentOut</structname>
      C struct, which the function must fill with result data.

<programlisting>
typedef struct spgInnerConsistentIn
{
    ScanKey     scankeys;       /* array of operators and comparison values */
    ScanKey     orderbys;       /* array of ordering operators and comparison
                                 * values */
    int         nkeys;          /* length of scankeys array */
    int         norderbys;      /* length of orderbys array */

    Datum       reconstructedValue;     /* value reconstructed at parent */
    void       *traversalValue; /* opclass-specific traverse value */
    MemoryContext traversalMemoryContext;   /* put new traverse values here */
    int         level;          /* current level (counting from zero) */
    bool        returnData;     /* original data must be returned? */

    /* Data from current inner tuple */
    bool        allTheSame;     /* tuple is marked all-the-same? */
    bool        hasPrefix;      /* tuple has a prefix? */
    Datum       prefixDatum;    /* if so, the prefix value */
    int         nNodes;         /* number of nodes in the inner tuple */
    Datum      *nodeLabels;     /* node label values (NULL if none) */
} spgInnerConsistentIn;

typedef struct spgInnerConsistentOut
{
    int         nNodes;         /* number of child nodes to be visited */
    int        *nodeNumbers;    /* their indexes in the node array */
    int        *levelAdds;      /* increment level by this much for each */
    Datum      *reconstructedValues;    /* associated reconstructed values */
    void      **traversalValues;        /* opclass-specific traverse values */
    double    **distances;              /* associated distances */
} spgInnerConsistentOut;
</programlisting>

       The array <structfield>scankeys</structfield>, of length <structfield>nkeys</structfield>,