error in the docs for ranking

[fabfabi]

The code snippet in the docs to showcase how to rank produces an error

ranker = xgb.XGBRanker(tree_method="hist",
                       lambdarank_num_pair_per_sample=8, 
                       objective="rank:ndcg", 
                       lambdarank_pair_method="topk")
ranker.fit(X, y, qid=qid)

XGBoostError: [08:38:16] /workspace/src/data/data.cc:532: Check failed: non_dec: qid must be sorted in non-decreasing order along with data.
Stack trace:

to fix it

ranker = xgb.XGBRanker(tree_method="hist",
                       lambdarank_num_pair_per_sample=8, 
                       objective="rank:ndcg", 
                       lambdarank_pair_method="topk")
ranker.fit(X, y, qid=qid[sorted_idx])

[hcho3]

Fixed in #10143

[getsanjeevdubey]

XGBoostError: [08:16:16] /workspace/src/data/data.cc:539: Check failed: non_dec: qid must be sorted in non-decreasing order along with data.
Stack trace:
[bt] (0) /opt/conda/lib/python3.8/site-packages/xgboost/lib/libxgboost.so(+0x22d7cc) [0x7f62199ee7cc]
[bt] (1) /opt/conda/lib/python3.8/site-packages/xgboost/lib/libxgboost.so(+0x4b4468) [0x7f6219c75468]
[bt] (2) /opt/conda/lib/python3.8/site-packages/xgboost/lib/libxgboost.so(+0x4b4850) [0x7f6219c75850]
[bt] (3) /opt/conda/lib/python3.8/site-packages/xgboost/lib/libxgboost.so(XGDMatrixSetInfoFromInterface+0xb2) [0x7f62198f5b42]
[bt] (4) /opt/conda/lib/python3.8/lib-dynload/../../libffi.so.7(+0x69ed) [0x7f62839279ed]
[bt] (5) /opt/conda/lib/python3.8/lib-dynload/../../libffi.so.7(+0x6077) [0x7f6283927077]
[bt] (6) /opt/conda/lib/python3.8/lib-dynload/_ctypes.cpython-38-x86_64-linux-gnu.so(_ctypes_callproc+0x2f3) [0x7f62827f3983]
[bt] (7) /opt/conda/lib/python3.8/lib-dynload/_ctypes.cpython-38-x86_64-linux-gnu.so(+0x10334) [0x7f62827f4334]
[bt] (8) /opt/conda/bin/python(_PyObject_MakeTpCall+0x31e) [0x564c33129ebe]

[getsanjeevdubey]

@hcho3 Please help; Copy pasted the documentation code; still some error;
Python 3.8.10

[trivialfis]

Opened a PR for the fix: #10539 .