在Oracle中使用TO_NUMBER函数遇到奇怪的问题 [英] Getting weird issue with TO_NUMBER function in Oracle

问题描述

如果记录数超过特定数目n，则在varchar2列的where子句中执行to_number函数时，我遇到了间歇性问题.我使用n是因为没有确切的记录数量.在一个DB上，它发生在n为一百万时，而在另一个DB上为0.1.百万.

I have been getting an intermittent issue when executing to_number function in the where clause on a varchar2 column if number of records exceed a certain number n. I used n as there is no exact number of records on which it happens. On one DB it happens after n was 1 million on another when it was 0.1. million.

例如我有一个具有1000万条记录的表，说表国家/地区具有包含数字数据和ID的field1 varchar2

E.g. I have a table with 10 million records say Table Country which has field1 varchar2 containing numberic data and Id

如果我以查询为例

select * 
from country 
where to_number(field1) = 23
and id >1 and id < 100000

这有效

但是如果我进行查询

select * 
from country 
where to_number(field1) = 23 
and id >1 and id < 100001

无法说出无效号码

接下来，我尝试查询

select * 
from country
where to_number(field1) = 23 
and id >2 and id < 100001

它再次起作用

由于我只有无效的号码，所以很混乱，但是在日志文件中却说

As I only got invalid number it was confusing, but in the log file it said

Memory Notification: Library Cache Object loaded into SGA
Heap size 3823K exceeds notification threshold (2048K)
KGL object name :with sqlplan as (
    select c006 object_owner, c007 object_type,c008 object_name
      from htmldb_collections
     where COLLECTION_NAME='HTMLDB_QUERY_PLAN'
       and c007 in ('TABLE','INDEX','MATERIALIZED VIEW','INDEX (UNIQUE)')),
ws_schemas as(
    select schema 
      from wwv_flow_company_schemas
     where security_group_id = :flow_security_group_id),
t as(
        select s.object_owner table_owner,s.object_name table_name,
               d.OBJECT_ID
          from sqlplan s,sys.dba_objects d

似乎与SGA大小有关，但是google在这方面没有给我太多帮助.

It seems its related to SGA size, but google did not give me much help on this.

对于大数据的TO_NUMBER或oracle函数，有人对这个问题有任何想法吗?

Does anyone have any idea about this issue with TO_NUMBER or oracle functions for large data?

推荐答案

假定您知道给定范围的ID始终将导致field1包含数字数据，您可以改为执行以下操作:

Assuming you know that the given range of ids will always result in field1 containing numeric data, you could do this instead:

select *
from (
  select /*+NO_MERGE*/ * 
  from country 
  where id >1 and id < 100000
)
where to_number(field1) = 23;

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