ALL_INDEXES描述了与索引有关的信息，为了使部分字段的内容更准确，我们需要通过analyze或者dbms_stats包来收集与索引有关的统计信息（这部分字段标记为带*）。
首先看一下官网给出的各个字段的解释：
| Column | Datatype | NULL | Description |
|---|---|---|---|
| OWNER | VARCHAR2(30) | NOT NULL | Owner of the index（索引拥有者） |
| INDEX_NAME | VARCHAR2(30) | NOT NULL | Name of the index |
| INDEX_TYPE | VARCHAR2(27) | Type of the index: NORMAL NORMAL/REV BITMAP FUNCTION-BASED NORMAL FUNCTION-BASED NORMAL/REV FUNCTION-BASED BITMAP CLUSTER IOT - TOP (索引组织表对应的索引，注意IOT - TOP 之间存有空格，个人观察：表的类型为IOT;对应索引类型为IOT - TOP;对应overflow表类型为IOT-OVERFLOW) DOMAIN（自定义索引类型） |
|
| TABLE_OWNER | VARCHAR2(30) | NOT NULL | Owner of the indexed object |
| TABLE_NAME | VARCHAR2(30) | NOT NULL | Name of the indexed object |
| TABLE_TYPE | CHAR(5) | Type of the indexed object: NEXT OBJECT INDEX TABLE CLUSTER VIEW SYNONYM SEQUENCE |
|
| UNIQUENESS | VARCHAR2(9) | Indicates whether the index is unique (UNIQUE) or nonunique (NONUNIQUE) | |
| COMPRESSION | VARCHAR2(8) | Indicates whether index compression is enabled (ENABLED) or not (DISABLED) | |
| PREFIX_LENGTH | NUMBER | Number of columns in the prefix of the compression key（索引压缩中被压缩的字段数量，唯一索引最大值为索引列数-1，非唯一索引最大值为索引列数） | |
| TABLESPACE_NAME | VARCHAR2(30) | Name of the tablespace containing the index | |
| INI_TRANS | NUMBER | Initial number of transactions | |
| MAX_TRANS | NUMBER | Maximum number of transactions | |
| INITIAL_EXTENT | NUMBER | Size of the initial extent | |
| NEXT_EXTENT | NUMBER | Size of secondary extents | |
| MIN_EXTENTS | NUMBER | Minimum number of extents allowed in the segment | |
| MAX_EXTENTS | NUMBER | Maximum number of extents allowed in the segment | |
| PCT_INCREASE | NUMBER | Percentage increase in extent size | |
| PCT_THRESHOLD | NUMBER | Threshold percentage of block space allowed per index entry | |
| INCLUDE_COLUMN | NUMBER | Column ID of the last column to be included in index-organized table primary key (non-overflow) index. This column maps to the COLUMN_ID column of the *_TAB_COLUMNS view(该字段具体的含义参见下文的解释). | |
| FREELISTS | NUMBER | Number of process freelists allocated to this segment | |
| FREELIST_GROUPS | NUMBER | Number of freelist groups allocated to this segment | |
| PCT_FREE | NUMBER | Minimum percentage of free space in a block | |
| LOGGING | VARCHAR2(3) | Indicates whether or not changes to the index are logged: YES NO |
|
| BLEVEL* | NUMBER | B*-Tree level (depth of the index from its root block to its leaf blocks). A depth of 0 indicates that the root block and leaf block are the same. | |
| LEAF_BLOCKS* | NUMBER | Number of leaf blocks in the index | |
| DISTINCT_KEYS* | NUMBER | Number of distinct indexed values. For indexes that enforce UNIQUE and PRIMARY KEY constraints, this value is the same as the number of rows in the table (*_TABLES.NUM_ROWS) | |
| AVG_LEAF_BLOCKS_PER_KEY* | NUMBER | Average number of leaf blocks in which each distinct value in the index appears, rounded to the nearest integer. For indexes that enforce UNIQUE and PRIMARY KEY constraints, this value is always 1. | |
| AVG_DATA_BLOCKS_PER_KEY* | NUMBER | Average number of data blocks in the table that are pointed to by a distinct value in the index rounded to the nearest integer. This statistic is the average number of data blocks that contain rows that contain a given value for the indexed columns. | |
| CLUSTERING_FACTOR* | NUMBER | Indicates the amount of order of the rows in the table based on the values of the index. If the value is near the number of blocks, then the table is very well ordered. In this case, the index entries in a sin |