Drop index (serial column) failed

[Alvin Peng]

Stado -> create table test(id serial, i int, c char, vc2 varchar(2)) partitioning key id on all;
OK
Stado -> create index idx on test(id);
OK
Stado -> show indexes on test;
+---------------------------------+
| indexname | isunique | columns |
+---------------------------------+
| IDX_SERIAL | NO | id |
| idx | NO | id |
+---------------------------------+
2 row(s).

It shows there are two indexes created. After reading the codes, I know that IDX_SERIAL is created by system. The index "idx" is not really created in underlying databases, while metadata is updated. This is because id is a serial column.

When trying to drop the index "idx", it failed.

Stado -> drop index idx;
SQLException: ERROR: ERROR: index "idx" does not exist

SqlDropIndex.java:
public void prepare() throws Exception {
...
if (columns.size() != 1
                    || columns.get(0) != table.getSerialColumn()) {
...

columns.get(0) != table.getSerialColumn() returns true, which is not the expected result.

The cause is when trying to create the index "idx", metadata is updated, and SyncCreateIndex.refresh() will re-read the table info. Thus, the columnlist will be re-created for the table.
However, the serialcolumn is cached and not updated.

SysTable.java:
...
    // Any table can have at most one serial column - this function
    // will get hold of that
    // particular sys column.
    public SysColumn getSerialColumn() {
        if (serialColumn == null) {
...

[Alvin Peng (pengalvin)]

/src/org/postgresql/stado/metadata/SysTable.java:

void readTableInfo(boolean force) throws XDBServerException {
...
add below line to clear cached data:

          serialColumn = null;