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MAPREDUCE-1224. Calling "SELECT t.* from <table> AS t" to get meta information is too expensive for big tables. Contributed by Spencer Ho.

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From: Thomas White <tomwhite@apache.org>

git-svn-id: https://svn.apache.org/repos/asf/incubator/sqoop/trunk@1149844 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Andrew Bayer 2011-07-22 20:03:29 +00:00
parent 8e813b95a4
commit 12827a1765
1 changed files with 2 additions and 1 deletions
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3
src/java/org/apache/hadoop/sqoop/manager/SqlManager.java
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@ -67,7 +67,8 @@ public SqlManager(final SqoopOptions opts) {
* be tuned per-database, but the main extraction loop is still inheritable. * be tuned per-database, but the main extraction loop is still inheritable.
*/ */
protected String getColNamesQuery(String tableName) { protected String getColNamesQuery(String tableName) {
return "SELECT t.* FROM " + tableName + " AS t"; // adding where clause to prevent loading a big table
return "SELECT t.* FROM " + tableName + " AS t WHERE 1=0";
} }
@Override @Override