pvargacl commented on a change in pull request #1087:
URL: https://github.com/apache/hive/pull/1087#discussion_r450793830
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File path:
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/txn/TxnHandler.java
##########
@@ -2032,28 +2077,61 @@ public void
seedWriteIdOnAcidConversion(InitializeTableWriteIdsRequest rqst)
// The initial value for write id should be 1 and hence we add 1 with
number of write ids
// allocated here
String s = "INSERT INTO \"NEXT_WRITE_ID\" (\"NWI_DATABASE\",
\"NWI_TABLE\", \"NWI_NEXT\") VALUES (?, ?, "
- + Long.toString(rqst.getSeeWriteId() + 1) + ")";
- pst = sqlGenerator.prepareStmtWithParameters(dbConn, s,
Arrays.asList(rqst.getDbName(), rqst.getTblName()));
+ + Long.toString(rqst.getSeedWriteId() + 1) + ")";
+ pst = sqlGenerator.prepareStmtWithParameters(dbConn, s,
Arrays.asList(rqst.getDbName(), rqst.getTableName()));
LOG.debug("Going to execute insert <" + s.replaceAll("\\?", "{}") +
">",
- quoteString(rqst.getDbName()), quoteString(rqst.getTblName()));
+ quoteString(rqst.getDbName()),
quoteString(rqst.getTableName()));
pst.execute();
LOG.debug("Going to commit");
dbConn.commit();
} catch (SQLException e) {
- LOG.debug("Going to rollback");
rollbackDBConn(dbConn);
- checkRetryable(dbConn, e, "seedWriteIdOnAcidConversion(" + rqst + ")");
- throw new MetaException("Unable to update transaction database "
- + StringUtils.stringifyException(e));
+ checkRetryable(dbConn, e, "seedWriteId(" + rqst + ")");
+ throw new MetaException("Unable to update transaction database " +
StringUtils.stringifyException(e));
} finally {
close(null, pst, dbConn);
unlockInternal();
}
} catch (RetryException e) {
- seedWriteIdOnAcidConversion(rqst);
+ seedWriteId(rqst);
}
+ }
+
+ @Override
+ public void seedTxnId(SeedTxnIdRequest rqst) throws MetaException {
+ try {
+ Connection dbConn = null;
+ Statement stmt = null;
+ try {
+ lockInternal();
+ dbConn = getDbConn(Connection.TRANSACTION_READ_COMMITTED);
+ stmt = dbConn.createStatement();
+ /*
+ * Locking the txnLock an exclusive way, we do not want to set the
txnId backward accidentally
+ * if there are concurrent open transactions
+ */
+ acquireTxnLock(stmt, false);
+ long highWaterMark = getHighWaterMark(stmt);
+ if (highWaterMark >= rqst.getSeedTxnId()) {
Review comment:
This is not about the writeIds, it is about the txnId. If you have a
data from a database where there were high amount of transaction and the
compaction run on the table, you will have some high txnId in the
visibilityTxnId in the name of the compacted folder.
If you then move this data to a cluster with less transaction (ex. a test
cluster) and you run the msck repair, you have to skip the txnId forward so the
next query will read the compacted folder. Here the race condition is, that
somehow the txnId sequence gets ahead of you between the check and the seeding
the value, in that case we throw this exception to not to set the sequence
backward. Anyway, in this case if you run the msck repair again it will
succeed, since the txnid will be high enough.
The writeId race condition won't cause a problem I think, since if some
other transaction allocated the first writeId the seedWriteId will fail on the
unique constraint on the table
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