Composing PSF Libraries

FishStore allows user to compose their own PSF libraries, register and deregister them on the fly. A PSF is a function that maps records to a value domain D. For a record r, we say it satisfy property (f, v) if and only if f(r) = v. For each registered PSF, FishStore will index all records whose f(r) does not evaluate to null.

To compose PSF libraries, user need to define their own PSF functions and compile them in a dynamic linking library (i.e., dll in Windows and .so in Linux/Unix). Generally, FishStore supports two types of PSFs, namely, General PSFs and Inline PSFs. This document will cover how user should define them in C++.

General PSFs

A general PSF maps a set of record fields to a bag of bytes which is represented as NullableStringRef under fishstore::core scope:

struct NullableStringRef {
  bool is_null = true;
  bool need_free = false;
  uint32_t size = 0;
  const char* payload = nullptr;
};

Specifically, is_null indicates if this is a null value, and need_free tells FishStore whether it requires be freed to avoid memory leakage.

Given a particular parser adapter adapter_t, a general PSF should be defined in the following function signature:

fishstore::core::NullableStringRef foo(const std::vector<typename adapter_t::field_t>& fields)}

For more details about parser adapters, please refer to this.

Inline PSFs

FishStore optimize specifically for PSFs with small fixed-size return values (to avoid allocating additional space in optional region). If a PSF returns a value less than 4 types, user can define it as:

fishstore::core::NullableInt foo(const std::vector<typename adapter_t::field_t>& fields)}

where fishstore::core::NullableInt is defined as below:

struct NullableInt {
  bool is_null;
  int32_t value;
};

Examples

In this folder, we provide two examples for PSF libraries:

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