关于java：通过JDBC将DDL与SELECT混合时，“错误：缓存的计划不得更改结果类型”

“ERROR: cached plan must not change result type” when mixing DDL with SELECT via JDBC

我在JDBC上遇到了一个与PostgreSQL有关的有趣问题(暂时无法在JDBC之外重现它)，

"ERROR: cached plan must not change result type"

重现此问题的最简单方法是使用以下代码：

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Connection c = getConnection();
c.setAutoCommit(true);
List<String> statements = Arrays.asList(
"create table t(a int)",
"select * from t",
"alter table t add b int",
"select * from t",
"alter table t add c int",
"select * from t",
"alter table t add d int",
"select * from t",
"alter table t add e int",
"select * from t",
"alter table t add f int",
"select * from t"
);

for (String statement : statements)
try (PreparedStatement s = c.prepareStatement(statement)) {
System.out.println(s);
s.execute();
}

以下代码可以正常工作的事实使我假设这是JDBC驱动程序中的一个非常微妙的错误(请注意，我只是在批处理中删除了第六条DDL语句)：

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Connection c = getConnection();
c.setAutoCommit(true);
List<String> statements = Arrays.asList(
"create table t(a int)",
"select * from t",
"alter table t add b int",
"select * from t",
"alter table t add c int",
"select * from t",
"alter table t add d int",
"select * from t",
"alter table t add e int",
"select * from t"
);

for (String statement : statements)
try (PreparedStatement s = c.prepareStatement(statement)) {
System.out.println(s);
s.execute();
}

似乎可以通过DISCARD ALL丢弃所有缓存的计划，但这会使情况变得更糟：

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Connection c = getConnection();
c.setAutoCommit(true);
List<String> statements = Arrays.asList(
"create table t(a int)",
"select * from t",
"alter table t add b int",
"select * from t",
"alter table t add c int",
"select * from t",
"alter table t add d int",
"select * from t",
"alter table t add e int",
"select * from t",
"alter table t add f int",
"discard all",
"select * from t"
);

for (String statement : statements)
try (PreparedStatement s = c.prepareStatement(statement)) {
System.out.println(s);
s.execute();
}

我遇到另一个错误消息

"ERROR: prepared statement"S_1" doesn't exist"

有谁知道解决方法？还是记录此错误的指针？有趣的是，它似乎与默认的准备阈值5有关