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[Syntax] Remove all EmptyStmt from the end of multi-statements list (#3140)

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to resolve the ISSUE: #3139 

When user execute query by some client library such as python MysqlDb, if user execute like:

     "select * from tbl1;"  (with a comma at the end of statement)
     
The sql parser will produce 2 statements: `SelectStmt` and `EmptyStmt`.
Here we discard the `EmptyStmt` to make it act like one single statement.

This is for some compatibility. Because in python MysqlDb, if the first `SelectStmt` results in
some warnings, it will try to execute a `SHOW WARNINGS` statement right after the 
SelectStmt, but before the execution of `EmptyStmt`. So there will be an exception:

     `(2014, "Commands out of sync; you can't run this command now")`

I though it is a flaw of python MysqlDb.
However, in order to maintain the consistency of user use, here we remove all EmptyStmt
at the end to prevent errors.(Leave at least one statement)

But if user execute statements like:

     `"select * from tbl1;;select 2"`
     
If first `select * from tbl1` has warnings, python MysqlDb will still throw exception.
This commit is contained in:
Mingyu Chen
2020-03-23 09:39:22 +08:00
committed by GitHub
parent dd8d748c55
commit 473a67a5b8
2 changed files with 33 additions and 3 deletions
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30
fe/src/main/java/org/apache/doris/common/util/SqlParserUtils.java
View File

@ -17,6 +17,7 @@
package org.apache.doris.common.util;
import org.apache.doris.analysis.EmptyStmt;
import org.apache.doris.analysis.SqlParser;
import org.apache.doris.analysis.StatementBase;
import org.apache.doris.common.AnalysisException;
@ -46,6 +47,33 @@ public class SqlParserUtils {
// get all parsed statements as a list
public static List<StatementBase> getMultiStmts(SqlParser parser) throws Exception {
return (List<StatementBase>) parser.parse().value;
List<StatementBase> stmts = (List<StatementBase>) parser.parse().value;
/*
* When user execute query by some client library such as python MysqlDb, if user execute like:
*
* "select * from tbl1;" (with a comma at the end of statement)
*
* The sql parser will produce 2 statements: SelectStmt and EmptyStmt.
* Here we discard the second EmptyStmt to make it act like one single statement.
* This is for some compatibility. Because in python MysqlDb, if the first SelectStmt results in
* some warnings, it will try to execute a 'SHOW WARNINGS' statement right after the SelectStmt,
* but before the execution of EmptyStmt. So there will be an exception:
*
* (2014, "Commands out of sync; you can't run this command now")
*
* I though it is a flaw of python MysqlDb.
* However, in order to maintain the consistency of user use, here we remove all EmptyStmt
* at the end to prevent errors.(Leave at least one statement)
*
* But if user execute statements like:
*
* "select * from tbl1;;select 2"
*
* If first "select * from tbl1" has warnings, python MysqlDb will still throw exception.
*/
while (stmts.size() > 1 && stmts.get(stmts.size() - 1) instanceof EmptyStmt) {
stmts.remove(stmts.size() - 1);
}
return stmts;
}
}

6
fe/src/test/java/org/apache/doris/planner/QueryPlanTest.java
View File

@ -19,7 +19,6 @@ package org.apache.doris.planner;
import org.apache.doris.analysis.CreateDbStmt;
import org.apache.doris.analysis.CreateDbStmtTest;
import org.apache.doris.analysis.CreateTableStmt;
import org.apache.doris.analysis.DropDbStmt;
import org.apache.doris.analysis.ShowCreateDbStmt;
@ -30,7 +29,6 @@ import org.apache.doris.qe.ConnectContext;
import org.apache.doris.qe.QueryState.MysqlStateType;
import org.apache.doris.utframe.UtFrameUtils;
import org.codehaus.jackson.map.ser.StdSerializers;
import org.junit.AfterClass;
import org.junit.Assert;
import org.junit.BeforeClass;
@ -308,6 +306,10 @@ public class QueryPlanTest {
sql = "SHOW VARIABLES LIKE 'lower_case_%';;;";
stmts = UtFrameUtils.parseAndAnalyzeStmts(sql, connectContext);
Assert.assertEquals(1, stmts.size());
sql = "SHOW VARIABLES LIKE 'lower_case_%';;;SHOW VARIABLES LIKE 'lower_case_%';";
stmts = UtFrameUtils.parseAndAnalyzeStmts(sql, connectContext);
Assert.assertEquals(4, stmts.size());
sql = "SHOW VARIABLES LIKE 'lower_case_%'";