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  5. PG_INDEX

PG_INDEX

PG_INDEX stores part of the information about indexes. The rest is mostly stored in PG_CLASS.

Table 1 PG_INDEX columns

Name

Type

Description

indexrelid

oid

OID of the pg_class entry for this index

indrelid

oid

OID of the pg_class entry for the table that uses this index

indnatts

smallint

Number of columns in the index (duplicate pg_class.relnatts)

indisunique

Boolean

Indicates a unique index if the value is true.

indisprimary

Boolean

Primary key of the table if the value is true Indisunique should always be true when the value of this column is true.

indisexclusion

Boolean

This index supports exclusion constraints if the value is true.

indimmediate

Boolean

A uniqueness check is performed upon data insertion if the value is true.

indisclustered

Boolean

The table was last clustered on this index if the value is true.

indisusable

Boolean

This index supports insert/select if the value is true.

indisvalid

Boolean

Indicates that this index is valid for queries if the value is true. If this column is false, this index is possibly incomplete and must still be modified by INSERT/UPDATE operations, but it cannot safely be used for queries. If it is a unique index, the uniqueness property is also not true.

indcheckxmin

Boolean

If its value is true, queries must not use the index until the xmin of this row in pg_index is below their TransactionXmin event horizon, because the table may contain broken HOT chains with incompatible rows that they can see.

indisready

Boolean

Indicates that the index is available for inserted data if the value is true. Otherwise, this index is ignored when data is inserted or modified.

indkey

int2vector

This is an array of indnatts values indicating that this index creates table columns. For example, a value of 1 3 indicates that the first and the third columns make up the index key. 0 in this array indicates that the corresponding index attribute is an expression over the table columns, rather than a simple column reference.

indcollation

oidvector

  

ID of each column used by the index

indclass

oidvector

For each column in the index key, this contains the OID of the operator class to use. See pg_opclass for details.

indoption

int2vector

Array of values that store per-column flag bits. The meaning of the bits is defined by the index's access method.

indexprs

pg_node_tree

Expression trees (in nodeToString() representation) for index attributes that are not simple column references. It is a list with one element for each zero entry in INDKEY. NULL if all index attributes are simple references.

indpred

pg_node_tree

Expression tree (in nodeToString() representation) for partial index predicate. If the index is not a partial index, this column is an empty string.