Optimize get_cansim_table_template() with expand_grid

[mountainMath]

Summary

Optimize get_cansim_table_template() by replacing iterative full_join operations with a single tidyr::expand_grid() call.

Before (iterative approach)

result <- tibble(...link="link", COORDINATE="")
for (i in seq_len(nrow(dimensions))) {
  result <- result %>%
    full_join(member, by="...link", relationship="many-to-many") %>%
    mutate(COORDINATE=ifelse(COORDINATE=="", memberId, paste0(COORDINATE, ".", memberId)))
}

After (vectorized approach)

result <- do.call(tidyr::expand_grid, dim_list)
coord_cols <- lapply(member_id_cols, function(col) result[[col]])
result$COORDINATE <- do.call(paste, c(coord_cols, sep="."))

Benchmark Results

Tested with installed package versions (mean of 5 runs each):

Table	Rows	Original	Optimized	Speedup
34-10-0013	50	0.0148s	0.0084s	43%
20-10-0001	660	0.0270s	0.0152s	44%
36-10-0402	13,143	0.0266s	0.0168s	37%
14-10-0287	32,076	0.0482s	0.0294s	39%
13-10-0096	66,528	0.0500s	0.0398s	20%

Correctness Verification

Output verified identical to original on all test tables:

• Column names match: ✓
• Row counts match: ✓
• Data identical (when sorted by COORDINATE): ✓

Table 34-10-0013: Columns identical: TRUE, Data identical (sorted): TRUE
Table 20-10-0001: Columns identical: TRUE, Data identical (sorted): TRUE
Table 14-10-0287: Columns identical: TRUE, Data identical (sorted): TRUE

Test Plan

• All existing tests pass (devtools::test() - 20 tests)
• Output verified identical on multiple tables
• Benchmarked with installed package versions

🤖 Generated with Claude Code