I'm trying to get the column list from newly created table(it is created in the java code).
The thing is that I do not get the columns.
The code works for tables that are already in the database, but if i create a new one and try to get the column info immediately it does not find any...
Update:
Here is full code that I used for testing:
#Test
public void testtest() throws Exception {
try (Connection conn = dataSource.getConnection()) {
String tableName = "Table_" + UUID.randomUUID().toString().replace("-", "");
try (Statement statement = conn.createStatement()) {
statement.executeUpdate(String.format("create table %s (id int primary key,name varchar(30));", tableName));
}
DatabaseMetaData metaData = conn.getMetaData();
try (ResultSet rs = metaData.getColumns(null, null, tableName, null)) {
int colsFound = 0;
while (rs.next()) {
colsFound++;
}
System.out.println(String.format("Found %s cols.", colsFound));
}
System.out.println(String.format("Autocommit is set to %s.", conn.getAutoCommit()));
}
}
The and the output:
Found 0 cols.
Autocommit is set to true.
The problem is with the case of your tablename:
String tableName = "Table_"
As that is an unquoted identifier (a good thing) the name is converted to lowercase when Postgres stores its name in the system catalog.
The DatabaseMetaData API calls are case sensitive ( "Table_" != "table_"), so you need to pass the lowercase tablename:
ResultSet rs = metaData.getColumns(null, null, tableName.toLowerCase(), null))
More details on how identifiers are using are in the manual: http://www.postgresql.org/docs/current/static/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
I have made simple test and it seems to work. I can create new table and show its columns using PostgreSQL JDBC (I use Jython):
conn = db.createStatement()
conn.execute("CREATE TABLE new_table (id SERIAL, txt VARCHAR(200))")
db_meta_data = db.getMetaData()
for tbl_name in ('date_test', 'new_table'):
print('\n-- %s --' % (tbl_name))
rs = db_meta_data.getColumns(None, None, tbl_name, None)
while (rs.next()):
print('%s:%s' % (rs.getString(3), rs.getString(4)))
conn.close()
This code shows columns for both already existing table: date_test and for just created new_table. I also added some code to close connection after CREATE TABLE but my results are always the same and correct.
Maybe it is problem with your JDBC driver. I use driver from postgresql-9.3-1100.jdbc41.jar.
It may be also problem with user permissions. Do you use the same user for both creating table and getting metadata? Is new table visible in psql, pgAdmin or other tool?
Other reason is that PostgreSQL uses transactions also for schema changes. So if you disabled default autocommit and closed connection your schema changes will be lost. Do you use db.setAutoCommit(false)?
You can also query PostgreSQL schema directly:
SELECT DISTINCT table_name, column_name
FROM information_schema.columns
WHERE table_schema='public'
AND table_name = 'new_table'
ORDER BY 1, 2
Strangely giving passing table name in lower case to getColumns method does work...thanks for the query Michał Niklas it got me on the right track.
Related
I have created the following H2 alias:
CREATE ALIAS INSERT_CHANGE_RECORD AS '
java.sql.ResultSet insertChangeRecord(final java.sql.Connection conn) throws java.sql.SQLException
{
String sql = "insert into `change_records` (`made_when`, `made_by`) values (CURRENT_TIMESTAMP(9), ''admin'');";
java.sql.PreparedStatement ps = conn.prepareStatement(sql, java.sql.Statement.RETURN_GENERATED_KEYS);
ps.executeUpdate();
java.sql.ResultSet results = ps.getGeneratedKeys() ;
return results;
}
';
Weirdly enough, when I call the alias (once) using call INSERT_CHANGE_RECORD(); 3 identical records are created in the table, instead of one.
When I use the following definition of the alias instead (the difference is that I actually retrieve the generated ID from the resultset), only 1 row is inserted.
CREATE ALIAS IF NOT EXISTS INSERT_CHANGE_RECORD AS '
Long insertChangeRecord(final java.sql.Connection conn) throws java.sql.SQLException
{
String sql = "insert into `change_records` (`made_when`, `made_by`) values (CURRENT_TIMESTAMP(9), ''admin'');";
java.sql.PreparedStatement ps = conn.prepareStatement(sql, java.sql.Statement.RETURN_GENERATED_KEYS);
ps.executeUpdate();
java.sql.ResultSet results = ps.getGeneratedKeys();
results.next();
return results.getLong(1);
}
';
Is this a bug in H2, or is there any reasonable explanation for this behavior? I'm using H2 2.1.210.
Here is the DDL of the table that I insert into.
CREATE TABLE IF NOT EXISTS `change_records` (
`id` BIGINT NOT NULL AUTO_INCREMENT CONSTRAINT `change_records_id_pk` PRIMARY KEY,
`made_when` TIMESTAMP (9) WITH TIME ZONE NOT NULL,
`made_by` VARCHAR NOT NULL
);
Function aliases returning a ResultSet are called multiple times. You need to check URL of passed connection. If it is equal to jdbc:columnlist:connection, you need to return an empty ResultSet with properly configured columns, you can use org.h2.tools.SimpleResultSet or some other implementation. These invocations are performed during compilation or recompilation of the query before its actual execution.
String url = conn.getMetaData().getURL();
if (url.equals("jdbc:columnlist:connection")) {
SimpleResultSet rs = new SimpleResultSet();
// With some connection options "id" should be used instead
rs.addColumn("ID", Types.BIGINT, 19, 0);
return rs;
}
// main code
This result set must have columns with exactly the same names and data types as your function normally returns. Be careful with column names, `id` usually means "ID", but if ;DATABASE_TO_LOWER=TRUE or ;DATABASE_TO_UPPER=FALSE were specified in JDBC URL used by your application, it means "id". Your function shouldn't modify any data during this execution, it is only asked about its metadata.
If URL is different, it is a real function call during execution of a query or other command and you need to execute your code.
See also an example:
https://github.com/h2database/h2database/blob/45b609dec0e45125e6a93f85c9018d34551332a1/h2/src/test/org/h2/samples/Function.java#L140
I am forced to use createSQLQuery to insert values into tables with an Identity column (the first column and the primary key) using hibernate. Using hibernate classes are not an option since the tables are created on the fly for each customer that is added to the system. I have run the query and it successfully inserts into the table. I then execute a "select scope_identity()" and it always returns null. "select ##Identity" works but that is not guaranteed to be the correct one. I have also tried to append "select scope_identity()" to the insert query. Then I tried query.list() and query.uniqueResult() both of which throw the hibernate exception of "No Results ..."
Session session = DatabaseEngine.getSessionFactory().openSession();
String queryString = "insert into table1 (dataid) values (1)"
SQLQuery query = session.createSQLQuery(insertQueryString);
query.executeUpdate();
query = session.createSQLQuery("select scope_identity()");
BigDecimal entryID = (BigDecimal)query.uniqueResult();
The simple example table is defined as follows:
"CREATE TABLE table1 (EntryID int identity(1,1) NOT NULL," +
"DataID int default 0 NOT NULL, " +
"PRIMARY KEY (EntryID))";
Is there a way I am missing to use scope_identity() with createSQLQuery?
Actually the SQLServerDialect class used by Hibernate uses the same "scope_identity()" too.
The reason why it's not working is because you need to execute those in the same statement or stored procedure.
If you execute the scope_identity() call in a separate statement, SQL Server will not be able to give you last inserted identity value.
You cannot do it with the SQLQuery, even Hibernate uses JDBC to accomplish this task. I wrote a test on GitHub to emulate this and it works like this:
Session session = entityManager.unwrap(Session.class);
final AtomicLong resultHolder = new AtomicLong();
session.doWork(connection -> {
try(PreparedStatement statement = connection.prepareStatement("INSERT INTO post VALUES (?) select scope_identity() ") ) {
statement.setString(1, "abc");
if ( !statement.execute() ) {
while ( !statement.getMoreResults() && statement.getUpdateCount() != -1 ) {
// do nothing until we hit the resultset
}
}
try (ResultSet rs = statement.getResultSet()) {
if(rs.next()) {
resultHolder.set(rs.getLong(1));
}
}
}
});
assertNotNull(resultHolder.get());
The code uses Java 8 lambdas instead of anonymous classes, but you can easily port it to Java 1.7 too.
actually i have googled a bit and i need corresponding SELECT command to following PostgreSQL shell command :
\dt schemaname.*
i managed to get all databases with following code :
Statement statement = (Statement) connection.createStatement();
ResultSet rs = statement
.executeQuery("SELECT datname FROM pg_database");
while (rs.next()) {
System.out.println("DB Name : " + rs.getString(1));
//i need another while here to list tables
//inside the selected database
}
i tried following statement, but no luck :
statement.executeQuery("SELECT table_schema,table_name FROM "
+ rs.getString(1)
+ " ORDER BY table_schema,table_name");
this is the error i am getting :
org.postgresql.util.PSQLException: ERROR: relation "template1" does not exist
Position: 37
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2102)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1835)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:500)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:374)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:254)
at com.isiran.rayten.rg.db.bare.wrapper.PGWrap.main(PGWrap.java:64)
If you use psql -E, it'll echo the actual queries that get run when you type commands such as \dt:
denis=# \dt public.*
********* QUERY **********
SELECT n.nspname as "Schema",
c.relname as "Name",
CASE c.relkind WHEN 'r' THEN 'table' WHEN 'v' THEN 'view' WHEN 'm' THEN 'materialized view' WHEN 'i' THEN 'index' WHEN 'S' THEN 'sequence' WHEN 's' THEN 'special' WHEN 'f' THEN 'foreign table' END as "Type",
pg_catalog.pg_get_userbyid(c.relowner) as "Owner"
FROM pg_catalog.pg_class c
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN ('r','s','')
AND n.nspname !~ '^pg_toast'
AND n.nspname ~ '^(public)$'
ORDER BY 1,2;
**************************
These queries can then be simplified or amended per your specific use-case.
Use the DatabaseMetaData object to query information, eg getTables(...):
DatabaseMetaData dbmd = connection.getMetaData();
try (ResultSet tables = dbmd.getTables(null, null, "%", new String[] { "TABLE" })) {
while (tables.next()) {
System.out.println(tables.getString("TABLE_NAME"));
}
}
This will return all tables in the database, you may need to specify values for catalog and/or schemaPattern to get a more specific result.
To list all tables from database you have to read table pg_catalog.pg_tables
But unfortunately you have to be logged-in in database.
So in place where you wrote comments
//i need another while here to list tables
//inside the selected database
Before loop for tables you need to log-in in this database.
I use oracle 11g with hibernate. Hibernate is configured to validate schema on startup, however for some reason it can not find one table and fails.
I have a strange situation where java.sql.DatabaseMetaData does not see one table (getTables returns empty result set) when it sees other table from the same schema.
So I have following situation:
String[] TYPES = {"TABLE", "VIEW"};
DatabaseMetaData meta = ...
meta.getTables(null, "SCHEMA_NAME", "TABLE1", TYPES).next(); // true
meta.getTables(null, "SCHEMA_NAME", "TABLE2", TYPES).next(); // false
But following queries are successfully executed:
select * from schemaName.table1
select * from schemaName.table2
More I can query a dictionary table and see both these tables:
select * from user_tables where table_name in ('TABLE1', 'TABLE2')
What could be a reason?
DatabaseMetaData md = connection.getMetaData();
ResultSet rs = md.getTables(null, null, "%", null);
while (rs.next()) {
System.out.println(rs.getString(3));
}
try the above code
The column 3 represents the Table_name
Click to know all the column numbers
Here is the problem: At my company we have a large database that we want to perform some automated operations in it. To test that we got a small sample of that data about 6 10MB sized csv files. We want to use H2 to test the results of our program in it. H2 Seemed to work fine with our previous cvs though they were, at most, 1000 entries long. When it comes to any of our 10MB files the command
insert into myschema.mytable (select * from csvread('mycsvfile.csv'));
reports a failure because one of the registries is supposedly duplicated and offends our primary key constraints.
Unique index or primary key violation: "PRIMARY_KEY_6 ON MYSCHEMA.MYTABLE(DATETIME, LARGENUMBER, KIND)"; SQL statement:
insert into myschema.mytable (select * from csvread('src/test/resources/h2/data/mycsvfile.csv')) [23001-148] 23001/23001
Breaking the mycsvfile.csv into smaller pieces I was able to see that the problem starts to appear after about 10000 rows inserted(though the number varies depending on what data I used). I could however insert more than 10000 rows if I broke the file into pieces and then ran the command individually. But even if I manage to insert all that data manually I need an automated method to fill the database.
Since running the command would not give me the row that was causing the problem I guessed that the problem could be some cache in the csvread routine.
Then I created a small java program that could insert the data in the H2 database manually. No matter whether I batched the commands, closed and opened the connection for 1000 rows h2 reported that I was trying to duplicate an entry in the database.
org.h2.jdbc.JdbcSQLException: Unique index or primary key violation: "PRIMARY_KEY_6 ON MYSCHEMA.MYTABLE(DATETIME, LARGENUMBER, KIND)"; SQL statement:
INSERT INTO myschema.mytable VALUES ( '1997-10-06 01:00:00.0',25485116,1.600,0,18 ) [23001-148]
Doing a normal search for that registry using emacs I can find that the registry is not duplicated as the datetime column is unique in the whole dataset.
I cannot give that data for you to test since the company sells that information. But here is how my table definition is like.
create table myschema.mytable (
datetime timestamp,
largenumber numeric(8,0) references myschema.largenumber(largecode),
value numeric(8,3) not null,
flag numeric(1,0) references myschema.flag(flagcode),
kind smallint references myschema.kind(kindcode),
primary key (datetime, largenumber, kind)
);
This is how our csv looks like:
datetime,largenumber,value,flag,kind
1997-06-11 16:45:00.0,25485116,0.710,0,18
1997-06-11 17:00:00.0,25485116,0.000,0,18
1997-06-11 17:15:00.0,25485116,0.000,0,18
1997-06-11 17:30:00.0,25485116,0.000,0,18
And the java code that would fill our test database(forgive my ugly code, I got desperate :)
private static void insertFile(MyFile file) throws SQLException {
int updateCount = 0;
ResultSet rs = Csv.getInstance().read(file.toString(), null, null);
ResultSetMetaData meta = rs.getMetaData();
Connection conn = DriverManager.getConnection(
"jdbc:h2:tcp://localhost/mytestdatabase", "sa", "pass");
rs.next();
while (rs.next()) {
Statement stmt = conn.createStatement();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < meta.getColumnCount(); i++) {
if (i == 0)
sb.append("'" + rs.getString(i + 1) + "'");
else
sb.append(rs.getString(i + 1));
sb.append(',');
}
updateCount++;
if (sb.length() > 0)
sb.deleteCharAt(sb.length() - 1);
stmt.execute(String.format(
"INSERT INTO myschema.mydatabase VALUES ( %s ) ",
sb.toString()));
if (updateCount == 1000) {
conn.close();
conn = DriverManager.getConnection(
"jdbc:h2:tcp://localhost/mytestdatabase", "sa", "pass");
updateCount = 0;
}
}
if (!conn.isClosed()) {
conn.close();
}
rs.close();
}
I'll be glad to provide more information if requested.
EDIT
#Randy I always check if the database is clean before running the command and in my java program I have a routine to delete all data from a file that fails to be inserted.
select * from myschema.mytable where largenumber = 25485116;
DATETIME LARGENUMBER VALUE FLAG KIND
(no rows, 8 ms)
The only thing that I can think of is that there is a trigger on the table that sets the timestamp to "now". Although that would not explain why you are successful with a few rows, it would explain why the primary key is being violated.