for the first index column?</entry>

</row>

<row>

<entry><structfield>amindexnulls</structfield></entry>

<entry><type>bool</type></entry>

<entry></entry>

<entry>Does the access method support null index entries?</entry>

</row>

<row>

<entry><structfield>amsearchnulls</structfield></entry>

<entry><type>bool</type></entry>

<entry><quote>Build new index</quote> function</entry>

</row>

<row>

<entry><structfield>ambuildempty</structfield></entry>

<entry><type>regproc</type></entry>

<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>

<entry><quote>Build empty index</quote> function</entry>

</row>

<row>

<entry><structfield>ambulkdelete</structfield></entry>

<entry><type>regproc</type></entry>

where no indexable restriction clause is given for the first index column.

When <structfield>amcanmulticol</structfield> is false,

<structfield>amoptionalkey</structfield> essentially says whether the

access methodallows full-index scans without any restriction clause.

access methodsupports full-index scans without any restriction clause.

Access methods that support multiple index columns <emphasis>must</>

support scans that omit restrictions on any or all of the columns after

the first; however they are permitted to require some restriction to

appear for the first index column, and this is signaled by setting

<structfield>amoptionalkey</structfield> false.

<structfield>amindexnulls</structfield> asserts that index entries are

created for NULL key values. Since most indexable operators are

One reason that an index AM might set

<structfield>amoptionalkey</structfield> false is if it doesn't index

NULLs. Since most indexable operators are

strict and hence cannot return TRUE for NULL inputs,

it is at first sight attractive to not store index entries for null values:

they could never be returned by an index scan anyway. However, this

used to scan for rows with <literal>a = 4</literal>, which is wrong if the

index omits rows where <literal>b</> is null.

It is, however, OK to omit rows where the first indexed column is null.

Thus, <structfield>amindexnulls</structfield> should be set true only if the

index access method indexes all rows, including arbitrary combinations of

null values. An index access method that sets

<structfield>amindexnulls</structfield> may also set

An index access method that does index nulls may also set

<structfield>amsearchnulls</structfield>, indicating that it supports

<literal>IS NULL</> and <literal>IS NOT NULL</> clauses as search

conditions.

errmsg("cannot cluster on partial index \"%s\"",

RelationGetRelationName(OldIndex))));

if (!OldIndex->rd_am->amindexnulls)

{

AttrNumbercolno;

colno=OldIndex->rd_index->indkey.values[0];

if (colno>0)

{

if (!OldHeap->rd_att->attrs[colno-1]->attnotnull)

ereport(ERROR,

(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),

errmsg("cannot cluster on index \"%s\" because access method does not handle null values",

RelationGetRelationName(OldIndex)),

?errhint("You might be able to work around this by marking column \"%s\" NOT NULL, or use ALTER TABLE ... SET WITHOUT CLUSTER to remove the cluster specification from the table.",

NameStr(OldHeap->rd_att->attrs[colno-1]->attname))

:errhint("You might be able to work around this by marking column \"%s\" NOT NULL.",

NameStr(OldHeap->rd_att->attrs[colno-1]->attname))));

}

elseif (colno<0)

{

}

ereport(ERROR,

(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),

errmsg("cannot cluster on expressional index \"%s\" because its index access method does not handle null values",

RelationGetRelationName(OldIndex))));

}

boolamcanunique;/* does AM support UNIQUE indexes? */

boolamcanmulticol;/* does AM support multi-column indexes? */

boolamoptionalkey;/* can query omit key for the first column? */

boolamindexnulls;/* does AM support NULL index entries? */

boolamsearchnulls;/* can AM search for NULL/NOT NULL entries? */

boolamstorage;/* can storage type differ from column type? */

boolamclusterable;/* does AM support cluster command? */

#defineAnum_pg_am_amcanunique7

#defineAnum_pg_am_amcanmulticol8

#defineAnum_pg_am_amoptionalkey9

#defineAnum_pg_am_amindexnulls10

#defineAnum_pg_am_amsearchnulls11

#defineAnum_pg_am_amstorage12

#defineAnum_pg_am_amclusterable13

#defineAnum_pg_am_amkeytype14

#defineAnum_pg_am_aminsert15

#defineAnum_pg_am_ambeginscan16

#defineAnum_pg_am_amgettuple17

#defineAnum_pg_am_amgetbitmap18

#defineAnum_pg_am_amrescan19

#defineAnum_pg_am_amendscan20

#defineAnum_pg_am_ammarkpos21

#defineAnum_pg_am_amrestrpos22

#defineAnum_pg_am_ambuild23

#defineAnum_pg_am_ambuildempty24

#defineAnum_pg_am_ambulkdelete25

#defineAnum_pg_am_amvacuumcleanup26

#defineAnum_pg_am_amcostestimate27

#defineAnum_pg_am_amoptions28

#defineAnum_pg_am_amsearchnulls10

#defineAnum_pg_am_amstorage11

#defineAnum_pg_am_amclusterable12

#defineAnum_pg_am_amkeytype13

#defineAnum_pg_am_aminsert14

#defineAnum_pg_am_ambeginscan15

#defineAnum_pg_am_amgettuple16

#defineAnum_pg_am_amgetbitmap17

#defineAnum_pg_am_amrescan18

#defineAnum_pg_am_amendscan19

#defineAnum_pg_am_ammarkpos20

#defineAnum_pg_am_amrestrpos21

#defineAnum_pg_am_ambuild22

#defineAnum_pg_am_ambuildempty23

#defineAnum_pg_am_ambulkdelete24

#defineAnum_pg_am_amvacuumcleanup25

#defineAnum_pg_am_amcostestimate26

#defineAnum_pg_am_amoptions27

DATA(insertOID=403 (btree51tfttttttft0btinsertbtbeginscanbtgettuplebtgetbitmapbtrescanbtendscanbtmarkposbtrestrposbtbuildbtbuildemptybtbulkdeletebtvacuumcleanupbtcostestimatebtoptions ));

DATA(insertOID=403 (btree51tftttttft0btinsertbtbeginscanbtgettuplebtgetbitmapbtrescanbtendscanbtmarkposbtrestrposbtbuildbtbuildemptybtbulkdeletebtvacuumcleanupbtcostestimatebtoptions ));

DESCR("b-tree index access method");

#defineBTREE_AM_OID 403

DATA(insertOID=405 (hash11fftfffffff23hashinserthashbeginscanhashgettuplehashgetbitmaphashrescanhashendscanhashmarkposhashrestrposhashbuildhashbuildemptyhashbulkdeletehashvacuumcleanuphashcostestimatehashoptions ));

DATA(insertOID=405 (hash11fftffffff23hashinserthashbeginscanhashgettuplehashgetbitmaphashrescanhashendscanhashmarkposhashrestrposhashbuildhashbuildemptyhashbulkdeletehashvacuumcleanuphashcostestimatehashoptions ));

DESCR("hash index access method");

#defineHASH_AM_OID 405

DATA(insertOID=783 (gist08ftfftttttt0gistinsertgistbeginscangistgettuplegistgetbitmapgistrescangistendscangistmarkposgistrestrposgistbuildgistbuildemptygistbulkdeletegistvacuumcleanupgistcostestimategistoptions ));

DATA(insertOID=783 (gist08ftffttttt0gistinsertgistbeginscangistgettuplegistgetbitmapgistrescangistendscangistmarkposgistrestrposgistbuildgistbuildemptygistbulkdeletegistvacuumcleanupgistcostestimategistoptions ));

DESCR("GiST index access method");

#defineGIST_AM_OID 783

DATA(insertOID=2742 (gin05ffffttfftf0gininsertginbeginscan-gingetbitmapginrescanginendscanginmarkposginrestrposginbuildginbuildemptyginbulkdeleteginvacuumcleanupgincostestimateginoptions ));

DATA(insertOID=2742 (gin05ffffttftf0gininsertginbeginscan-gingetbitmapginrescanginendscanginmarkposginrestrposginbuildginbuildemptyginbulkdeleteginvacuumcleanupgincostestimateginoptions ));

DESCR("GIN index access method");

#defineGIN_AM_OID 2742