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Qihan Zhang (张启涵)

A Brief Introduction

My name is Qihan Zhang, an incoming CS PhD student in 2025 Fall. I’m fortunate advised by Professor Ibrahim Sabek and Mengyuan Li. I finished my CS major undergraduate study from UESTC (University of Electronic Science and Technology of China), and I’m fortunate advised by Professor Hancong Duan. My interset lies in Database Systems (especially Query Optimizer), the intersection between AI and DB, the intersection between Security and DB, .etc.

The field of databases is a delicate place: one can both see the elegance and complexity of system design, and glimpse the mundane daily life through the lens of software development. As AI technology continues to evolve rapidly, data serves as both fuel for models and nourishment for the development of databases. I believe this field requires profound accumulation but also maintains its openness and endless possibilities.

The story begins from an afternoon in summer, starting with the definition of data, knowledge, information. The youth drifts into a drowsy slumber. He still believes that the essence of university lies in cultivating virtue, being close to the people, and achieving the ultimate good. Yet today, rat race is alomost everywhere and unavoidable. People use increasingly dazzling exteriors to cover up their fading and anxious hearts. Slowly awakening from sleep, he looks back to find he has walked a long path. Has he grown up? Matured? Or become numb? In any case, there’s no going back.

News

• [Aug 2025] We have a new paper (co-first author) accepted by SIGMOD 2026, which discuss the possibility of using RAG to optimize the query execution plan, the results show great generalizability.

• [Jun 2025] We have a new paper (first author) accepted by VLDB 2025, which discuss the possibility of using lifelong reinforcement learning to optimize the query execution plan.

• [May 2025] I will attend the SoCalDB 2025 and present a poster there!

• [Apr 2025] We have a new workshop paper (co-first author) accepted by aiDM 2025, which co-occurs with the SIGMOD 2025!

• [Mar 2025] I officially join the USC Viterbi School of Engineering as a CS PhD student!

The Myth of Sisyphus

Push the stone along the fixed, irregular and steep mountain road using your mouse or control panel. Once you reach the top, watch it roll back down along the same path to the start, endlessly.

But one must imagine Sisyphus happy. —Albert Camus

The Iron House Metaphor

Imagine an iron house, completely sealed, without any windows or doors.
Inside it, people are sleeping, unaware of their approaching suffocation and death.
They will pass from sleep into death without suffering or sorrow, simply drifting away.
You stand here, conscious, facing this scene. You have two choices:

I hope that Chinese youth can shed negativity and focus on moving forward, without needing to listen to those who surrender and self-destruct. Let those who can take action do so, and let those who can speak voice their thoughts. Even with a spark of passion, shine like fireflies; you can also emit a little light in the darkness without waiting for a torch. —Xun Lu

The Perpetually Young at Heart

You,
At times look at me,
At times look at the clouds.

I feel,
When you look at me, you are far.
When you look at the clouds, you are near.

I, along with countless
Unhatched pebbles,
Am piled together.

The blue stream crawls over,
Swallowing us whole,
Then quietly spitting us out.

There is nothing else—
Only the hope
That grass can stretch
Its shadow a little longer.

The night gave me black eyes,
But I use them to seek the light.

The clouds, gray and heavy,
Can never be washed clean.

We open our umbrellas,
Painting the sky completely black.

In the slowly drifting night,
Two pairs of twin stars
Seem to have no fixed path—
Only drawing near, then drifting apart...

The alley,
Twisting and long,
Has no doors,
No windows.

With an old key in hand,
I tap against the heavy wall.

Passing through solemn rocks,
I walk toward the shore.

"Speak," I say,
"I understand the language of the world."

The sea laughs,
Showing me
Birds that swim,
Fish that fly,
Sands that sing.

Yet to that eternal question,
It offers no reply.

In the evening glow,
You press your lips tightly together:
"Just fifteen minutes left."
So now, the tragedy begins.

"To be apart for ten years, a hundred years!"
"To be separated by a thousand miles, ten thousand miles!"
Suddenly, you flash a playful smile,
Revealing the truth of your youth.

"Forgot a line."
"Hmm, definitely forgot a line."
We never figured it out,
And the sun quietly slipped into rest.

Sunlight,
A sudden flash in the sky,
Quickly buried by dark clouds.

Torrential rain washes over,
The negatives of my soul.

After the rain,
A plain of water,
A stretch of silence.

Countless insect wings
No longer hum.

On the swollen, aching earth
Of purslane,
Water striders chase trembling ripples.

Petals—rosy red, pale blue—
Cling desperately to broken branches,
While foam trades stolen colors
In secret.

The little willow tree, far away,
With its hair tangled,
Sees itself for the first time—
Why is it not happy?

In the spring,
You wave your handkerchief gently—
Is it to send me away,
Or to call me back?

No, it is neither.
It is for nothing, for no reason.
Like petals drifting in water,
Like dew resting upon a flower...

Only shadows understand,
Only the wind can feel.
Only the butterfly startled by a sigh
Still flutters amidst the blossoms of the heart.

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I Am a Willful Child

I am a willful child— I want to paint windows everywhere on the earth, So that all eyes long used to darkness May learn to grow accustomed to light.

Perhaps I am a child spoiled by my mother— I am headstrong, I hope Every moment May glow with the beauty of colored crayons. I hope To draw upon my beloved white pages, To sketch a clumsy kind of freedom, To paint an eye that will never cry, A piece of sky, A feather and leaf that belong to that sky, A pale green evening, and an apple.

I want to paint the morning, To paint a smile The dew can behold, To paint the youngest loves That know no sorrow, To paint my imagined beloved— She has never seen dark clouds, Her eyes are the color of a clear, bright sky, She always watches me, Always watches, Never suddenly turning away.

I want to paint distant landscapes, To paint a clean horizon and trembling ripples, To paint countless happy little rivers, To paint hills Soft with pale fuzz. I will set them close together, Let them fall in love, Let every quiet consent, Every silent thrill of spring, Become a birthday bloom.

I also want to paint the future— I have never seen her, nor can I, Yet I know she is beautiful. I will paint her autumn coat, Paint the burning candles and maple leaves, Paint all those hearts snuffed out For love of her. I will paint a wedding, Paint each holiday that wakes too early— Adorned with glossy candy wrappers And illustrations from a northern fairy tale.

I am a willful child, I want to wipe away all misfortune, I want to fill the earth with windows, So all eyes accustomed to darkness May learn to love the light.

I want to paint the wind, To paint ranges of mountains ever higher, To paint the longing of eastern peoples, To paint the sea— Boundless, brimming with joyful sound.

At last, in a corner of the page, I still want to paint myself— To paint a koala, Sitting in Victoria’s dusky forests, Quiet atop a branch, Lost in thought. He has no home, No distant heart, Only a bounty of berry-like dreams, And very large, very gentle eyes.

I am hoping, I am imagining, But I do not know why I have never been given crayons, Never gained a single colored moment. I have only myself, My fingers, and my wounds. I must tear those beloved blank pages, Let them search for butterflies, Let them vanish from today.

I am a child, A child spoiled by the mother of dreams. I am willful. ——Cheng Gu, one of Chinese Misty Poets.