原創作品，出自 “深藍的blog” 部落格，歡迎轉載，轉載時請務必註明出處，否則追究版權法律責任。

今天在為某系統資料庫結構整理升級指令碼時，遇到了“命名位元組過長的錯誤”，類似於下面的截圖語句：

        由於升級的結構中對於欄位名的命名根據業務進行了修改，出現了命名過長的情況。

這裡想說一下，對於oracle，表名、欄位名等物件命名位元組個數限制在了30個位元組！是無法更改的，這是oracle的固化設定。

        我們可以通過檢視資料庫字典進一步驗證一下。先思考一下，哪裡可以獲得關於這類命名的資訊呢？有沒有想到USER_TAB_COLUMNS,USER_CONSTRAINTS這一類的檢視。我們來做一個驗證。

實驗:

        在sys使用者下，檢視user_tables這個檢視，可以發現在table_name這個欄位，型別為varchar，長度為30，這裡記錄的表的名稱，如下：

再進一步檢視檢視的結構，如下：

create or replace view user_tables(table_name, tablespace_name, cluster_name, iot_name, status, pct_free, pct_used, ini_trans, max_trans, initial_extent, next_extent, min_extents, max_extents, pct_increase, freelists, freelist_groups, logging, backed_up, num_rows, blocks, empty_blocks, avg_space, chain_cnt, avg_row_len, avg_space_freelist_blocks, num_freelist_blocks, degree, instances, cache, table_lock, sample_size, last_analyzed, partitioned, iot_type, temporary, secondary, nested, buffer_pool, flash_cache, cell_flash_cache, row_movement, global_stats, user_stats, duration, skip_corrupt, monitoring, cluster_owner, dependencies, compression, compress_for, dropped, read_only, segment_created, result_cache)asselect o.name,       decode(bitand(t.property,2151678048), 0, ts.name,              decode(t.ts#, 0, null, ts.name)),       decode(bitand(t.property, 1024), 0, null, co.name),       decode((bitand(t.property, 512)+bitand(t.flags, 536870912)),              0, null, co.name),       decode(bitand(t.trigflag, 1073741824), 1073741824, 'UNUSABLE', 'VALID'),       decode(bitand(t.property, 32+64), 0, mod(t.pctfree$, 100), 64, 0, null),       decode(bitand(ts.flags, 32), 32, to_number(NULL),          decode(bitand(t.property, 32+64), 0, t.pctused$, 64, 0, null)),       decode(bitand(t.property, 32), 0, t.initrans, null),       decode(bitand(t.property, 32), 0, t.maxtrans, null),       decode(bitand(t.property, 17179869184), 17179869184,                     ds.initial_stg * ts.blocksize,                     s.iniexts * ts.blocksize),       decode(bitand(t.property, 17179869184), 17179869184,              ds.next_stg * ts.blocksize,              s.extsize * ts.blocksize),       decode(bitand(t.property, 17179869184), 17179869184,              ds.minext_stg, s.minexts),       decode(bitand(t.property, 17179869184), 17179869184,              ds.maxext_stg, s.maxexts),       decode(bitand(ts.flags, 3), 1, to_number(NULL),              decode(bitand(t.property, 17179869184), 17179869184,                            ds.pctinc_stg, s.extpct)),       decode(bitand(ts.flags, 32), 32, to_number(NULL),         decode(bitand(o.flags, 2), 2, 1,                decode(bitand(t.property, 17179869184), 17179869184,                       ds.frlins_stg, decode(s.lists, 0, 1, s.lists)))),       decode(bitand(ts.flags, 32), 32, to_number(NULL),         decode(bitand(o.flags, 2), 2, 1,                decode(bitand(t.property, 17179869184), 17179869184,                       ds.maxins_stg, decode(s.groups, 0, 1, s.groups)))),       decode(bitand(t.property, 32+64), 0,                decode(bitand(t.flags, 32), 0, 'YES', 'NO'), null),       decode(bitand(t.flags,1), 0, 'Y', 1, 'N', '?'),       t.rowcnt,       decode(bitand(t.property, 64), 0, t.blkcnt, null),       decode(bitand(t.property, 64), 0, t.empcnt, null),       decode(bitand(t.property, 64), 0, t.avgspc, null),       t.chncnt, t.avgrln, t.avgspc_flb,       decode(bitand(t.property, 64), 0, t.flbcnt, null),       lpad(decode(t.degree, 32767, 'DEFAULT', nvl(t.degree,1)),10),       lpad(decode(t.instances, 32767, 'DEFAULT', nvl(t.instances,1)),10),       lpad(decode(bitand(t.flags, 8), 8, 'Y', 'N'),5),       decode(bitand(t.flags, 6), 0, 'ENABLED', 'DISABLED'),       t.samplesize, t.analyzetime,       decode(bitand(t.property, 32), 32, 'YES', 'NO'),       decode(bitand(t.property, 64), 64, 'IOT',               decode(bitand(t.property, 512), 512, 'IOT_OVERFLOW',               decode(bitand(t.flags, 536870912), 536870912, 'IOT_MAPPING', null))),       decode(bitand(o.flags, 2), 0, 'N', 2, 'Y', 'N'),       decode(bitand(o.flags, 16), 0, 'N', 16, 'Y', 'N'),       decode(bitand(t.property, 8192), 8192, 'YES',              decode(bitand(t.property, 1), 0, 'NO', 'YES')),       decode(bitand(o.flags, 2), 2, 'DEFAULT',              decode(bitand(decode(bitand(t.property, 17179869184), 17179869184,                            ds.bfp_stg, s.cachehint), 3),                            1, 'KEEP', 2, 'RECYCLE', 'DEFAULT')),       decode(bitand(o.flags, 2), 2, 'DEFAULT',              decode(bitand(decode(bitand(t.property, 17179869184), 17179869184,                            ds.bfp_stg, s.cachehint), 12)/4,                            1, 'KEEP', 2, 'NONE', 'DEFAULT')),       decode(bitand(o.flags, 2), 2, 'DEFAULT',              decode(bitand(decode(bitand(t.property, 17179869184), 17179869184,                            ds.bfp_stg, s.cachehint), 48)/16,                            1, 'KEEP', 2, 'NONE', 'DEFAULT')),       decode(bitand(t.flags, 131072), 131072, 'ENABLED', 'DISABLED'),       decode(bitand(t.flags, 512), 0, 'NO', 'YES'),       decode(bitand(t.flags, 256), 0, 'NO', 'YES'),       decode(bitand(o.flags, 2), 0, NULL,           decode(bitand(t.property, 8388608), 8388608,                  'SYS$SESSION', 'SYS$TRANSACTION')),       decode(bitand(t.flags, 1024), 1024, 'ENABLED', 'DISABLED'),       decode(bitand(o.flags, 2), 2, 'NO',           decode(bitand(t.property, 2147483648), 2147483648, 'NO',              decode(ksppcv.ksppstvl, 'TRUE', 'YES', 'NO'))),       decode(bitand(t.property, 1024), 0, null, cu.name),       decode(bitand(t.flags, 8388608), 8388608, 'ENABLED', 'DISABLED'),       case when (bitand(t.property, 32) = 32) then         null       when (bitand(t.property, 17179869184) = 17179869184) then         decode(bitand(ds.flags_stg, 4), 4, 'ENABLED', 'DISABLED')       else         decode(bitand(s.spare1, 2048), 2048, 'ENABLED', 'DISABLED')       end,       case when (bitand(t.property, 32) = 32) then         null       when (bitand(t.property, 17179869184) = 17179869184) then          decode(bitand(ds.flags_stg, 4), 4,          case when bitand(ds.cmpflag_stg, 3) = 1 then 'BASIC'               when bitand(ds.cmpflag_stg, 3) = 2 then 'OLTP'               else decode(ds.cmplvl_stg, 1, 'QUERY LOW',                                          2, 'QUERY HIGH',                                          3, 'ARCHIVE LOW',                                             'ARCHIVE HIGH') end,               null)       else         decode(bitand(s.spare1, 2048), 0, null,         case when bitand(s.spare1, 16777216) = 16777216   -- 0x1000000                   then 'OLTP'              when bitand(s.spare1, 100663296) = 33554432  -- 0x2000000                   then 'QUERY LOW'              when bitand(s.spare1, 100663296) = 67108864  -- 0x4000000                   then 'QUERY HIGH'              when bitand(s.spare1, 100663296) = 100663296 -- 0x2000000+0x4000000                   then 'ARCHIVE LOW'              when bitand(s.spare1, 134217728) = 134217728 -- 0x8000000                   then 'ARCHIVE HIGH'              else 'BASIC' end)       end,       decode(bitand(o.flags, 128), 128, 'YES', 'NO'),       decode(bitand(t.trigflag, 2097152), 2097152, 'YES', 'NO'),       decode(bitand(t.property, 17179869184), 17179869184, 'NO',              decode(bitand(t.property, 32), 32, 'N/A', 'YES')),       decode(bitand(t.property,16492674416640),2199023255552,'FORCE',                     4398046511104,'MANUAL','DEFAULT')from sys.ts$ ts, sys.seg$ s, sys.obj$ co, sys.tab$ t, sys.obj$ o,     sys.deferred_stg$ ds, sys.obj$ cx, sys.user$ cu, x$ksppcv ksppcv,     x$ksppi ksppiwhere o.owner# = userenv('SCHEMAID')  and o.obj# = t.obj#  and bitand(t.property, 1) = 0  and bitand(o.flags, 128) = 0  and t.bobj# = co.obj# (+)  and t.ts# = ts.ts#  and t.file# = s.file# (+)  and t.block# = s.block# (+)  and t.ts# = s.ts# (+)  and t.obj# = ds.obj# (+)  and t.dataobj# = cx.obj# (+)  and cx.owner# = cu.user# (+)  and ksppi.indx = ksppcv.indx  and ksppi.ksppinm = '_dml_monitoring_enabled';comment on table USER_TABLES is 'Description of the user''s own relational tables';comment on column USER_TABLES.TABLE_NAME is 'Name of the table';comment on column USER_TABLES.TABLESPACE_NAME is 'Name of the tablespace containing the table';comment on column USER_TABLES.CLUSTER_NAME is 'Name of the cluster, if any, to which the table belongs';comment on column USER_TABLES.IOT_NAME is 'Name of the index-only table, if any, to which the overflow or mapping table entry belongs';comment on column USER_TABLES.STATUS is 'Status of the table will be UNUSABLE if a previous DROP TABLE operation failed,VALID otherwise';comment on column USER_TABLES.PCT_FREE is 'Minimum percentage of free space in a block';comment on column USER_TABLES.PCT_USED is 'Minimum percentage of used space in a block';comment on column USER_TABLES.INI_TRANS is 'Initial number of transactions';comment on column USER_TABLES.MAX_TRANS is 'Maximum number of transactions';comment on column USER_TABLES.INITIAL_EXTENT is 'Size of the initial extent in bytes';comment on column USER_TABLES.NEXT_EXTENT is 'Size of secondary extents in bytes';comment on column USER_TABLES.MIN_EXTENTS is 'Minimum number of extents allowed in the segment';comment on column USER_TABLES.MAX_EXTENTS is 'Maximum number of extents allowed in the segment';comment on column USER_TABLES.PCT_INCREASE is 'Percentage increase in extent size';comment on column USER_TABLES.FREELISTS is 'Number of process freelists allocated in this segment';comment on column USER_TABLES.FREELIST_GROUPS is 'Number of freelist groups allocated in this segment';comment on column USER_TABLES.LOGGING is 'Logging attribute';comment on column USER_TABLES.BACKED_UP is 'Has table been backed up since last modification?';comment on column USER_TABLES.NUM_ROWS is 'The number of rows in the table';comment on column USER_TABLES.BLOCKS is 'The number of used blocks in the table';comment on column USER_TABLES.EMPTY_BLOCKS is 'The number of empty (never used) blocks in the table';comment on column USER_TABLES.AVG_SPACE is 'The average available free space in the table';comment on column USER_TABLES.CHAIN_CNT is 'The number of chained rows in the table';comment on column USER_TABLES.AVG_ROW_LEN is 'The average row length, including row overhead';comment on column USER_TABLES.AVG_SPACE_FREELIST_BLOCKS is 'The average freespace of all blocks on a freelist';comment on column USER_TABLES.NUM_FREELIST_BLOCKS is 'The number of blocks on the freelist';comment on column USER_TABLES.DEGREE is 'The number of threads per instance for scanning the table';comment on column USER_TABLES.INSTANCES is 'The number of instances across which the table is to be scanned';comment on column USER_TABLES.CACHE is 'Whether the table is to be cached in the buffer cache';comment on column USER_TABLES.TABLE_LOCK is 'Whether table locking is enabled or disabled';comment on column USER_TABLES.SAMPLE_SIZE is 'The sample size used in analyzing this table';comment on column USER_TABLES.LAST_ANALYZED is 'The date of the most recent time this table was analyzed';comment on column USER_TABLES.PARTITIONED is 'Is this table partitioned? YES or NO';comment on column USER_TABLES.IOT_TYPE is 'If index-only table, then IOT_TYPE is IOT or IOT_OVERFLOW or IOT_MAPPING else NULL';comment on column USER_TABLES.TEMPORARY is 'Can the current session only see data that it place in this object itself?';comment on column USER_TABLES.SECONDARY is 'Is this table object created as part of icreate for domain indexes?';comment on column USER_TABLES.NESTED is 'Is the table a nested table?';comment on column USER_TABLES.BUFFER_POOL is 'The default buffer pool to be used for table blocks';comment on column USER_TABLES.FLASH_CACHE is 'The default flash cache hint to be used for table blocks';comment on column USER_TABLES.CELL_FLASH_CACHE is 'The default cell flash cache hint to be used for table blocks';comment on column USER_TABLES.ROW_MOVEMENT is 'Whether partitioned row movement is enabled or disabled';comment on column USER_TABLES.GLOBAL_STATS is 'Are the statistics calculated without merging underlying partitions?';comment on column USER_TABLES.USER_STATS is 'Were the statistics entered directly by the user?';comment on column USER_TABLES.DURATION is 'If temporary table, then duration is sys$session or sys$transaction else NULL';comment on column USER_TABLES.SKIP_CORRUPT is 'Whether skip corrupt blocks is enabled or disabled';comment on column USER_TABLES.MONITORING is 'Should we keep track of the amount of modification?';comment on column USER_TABLES.CLUSTER_OWNER is 'Owner of the cluster, if any, to which the table belongs';comment on column USER_TABLES.DEPENDENCIES is 'Should we keep track of row level dependencies?';comment on column USER_TABLES.COMPRESSION is 'Whether table compression is enabled or not';comment on column USER_TABLES.COMPRESS_FOR is 'Compress what kind of operations';comment on column USER_TABLES.DROPPED is 'Whether table is dropped and is in Recycle Bin';comment on column USER_TABLES.READ_ONLY is 'Whether table is read only or not';comment on column USER_TABLES.SEGMENT_CREATED is 'Whether the table segment is created or not';comment on column USER_TABLES.RESULT_CACHE is 'The result cache mode annotation for the table';
 

我們可以由檢視結構中鎖定到三個地方，定位到來源，如下：

table_name

o.name

sys.obj$ o

可以發現，table_name欄位來源於sys.obj$中的name欄位，如下：

我們嘗試修改一下sys.obj$中name欄位的長度，如下：

        可以看到，我們是無法修改資料庫系統的字典欄位的定義。用同樣的方法，我們還可以檢視USER_TAB_COLUMNS,USER_CONSTRAINTS等檢視，會發現對於oracle，限制了命名的長度，都限制在了30個位元組。

        之後在網上搜了一下，發現對於不同的資料庫原來命名長度限制是不一樣的，摘錄如下：

原創作品，出自 “深藍的blog” 部落格，歡迎轉載，轉載時請務必註明出處，否則追究版權法律責任。

系列連結：