feat: implement LOAD_FILE scalar function for Document AI

[yanxf-git]

Implements BLOB LOAD_FILE(location_name, file_name) that reads a local file via a file:// LOCATION. Registered as T_FUN_SYS_LOAD_FILE=2087.

Adapted from OceanBase commit 28c25842 with seekdb-specific changes:

• Use POSIX open/pread instead of ObExternalDataAccessDriver (not in seekdb)
• Use 1-arg get_tenant_schema_guard (seekdb signature)
• Use 2-arg get_location_schema_by_name (seekdb signature)
• Drop MultimodeAlloctor (not needed for simple file read)
• Use ObString::prefix_match instead of 3-arg compare

Local verification: mysqltest ai_funcs/load_file.test PASS

Task Description

Solution Description

Passed Regressions

Upgrade Compatibility

Other Information

Release Note

[CLAassistant]

All committers have signed the CLA.

[LINxiansheng]

Document AI & IK Custom Dictionary Score

Document AI Functions Score
===========================
score: 50.00 / 100
load_file: 50 / 50
ai_split_document: 0 / 50

IK Custom Dictionary Score
==========================
score: 0.00 / 100
ik_custom_dict: 0 / 100

FTS Large Benchmark Score

FTS Large Benchmark Score
=========================
score: 0.00 / 100
mean_improvement: -2.32%
full_score_improvement: 50.00%

build_improvement: -2.34%
  build_ik_all_sec: baseline=35.2836, current=36.057, improvement=-2.19%
  build_ik_content_sec: baseline=28.3764, current=28.903, improvement=-1.86%
  build_beng_en_sec: baseline=14.7578, current=15.198, improvement=-2.98%
tokenize_improvement: -0.97%
  tokenize_ik_avg_ms: baseline=0.76478, current=0.7554, improvement=1.23%
  tokenize_beng_avg_ms: baseline=0.42262, current=0.436, improvement=-3.17%
query_improvement: -3.64%
  query_cn_avg_ms: baseline=16.6628, current=17.3785, improvement=-4.30%
  query_beng_avg_ms: baseline=24.3042, current=25.1852, improvement=-3.62%
  query_mixed_avg_ms: baseline=17.5593, current=18.1195, improvement=-3.19%
  query_limit_avg_ms: baseline=16.2334, current=16.7947, improvement=-3.46%

FTS Large Benchmark Report

========================================
FTS Large Benchmark Report
========================================
timestamp:              2026-07-15 08:39:38
label:                  vldb-ci-29399798056-1
git_head:               8143909
git_dirty:              0
rows:                   20000
batch:                  500
rounds:                 3000
query_rounds:           200
samples:                3
warmup:                 30
skip_load:              0
----------------------------------------
select1_avg_ms:         0.2097
select1_stdev_ms:       0.0010
raw_load_sec:           1.610
raw_load_rows_per_sec:  12422.4
build_ik_all_sec:       36.057
build_ik_content_sec:   28.903
build_beng_en_sec:      15.198
build_total_sec:        80.170
----------------------------------------
tokenize_ik_avg_ms:     0.7554
tokenize_ik_median_ms:  0.7556
tokenize_ik_stdev_ms:   0.0008
tokenize_beng_avg_ms:   0.4360
tokenize_beng_median_ms:0.4270
tokenize_beng_stdev_ms: 0.0147
----------------------------------------
query_cn_hits:          8001
query_cn_avg_ms:        17.3785
query_cn_stdev_ms:      0.0148
query_beng_hits:        11000
query_beng_avg_ms:      25.1852
query_beng_stdev_ms:    0.0373
query_mixed_hits:       7332
query_mixed_avg_ms:     18.1195
query_mixed_stdev_ms:   0.0554
query_limit_hits:       20
query_limit_avg_ms:     16.7947
query_limit_stdev_ms:   0.2910
========================================

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