test: migrate aggregation tests from duckdb, part4

[killme2008]

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What's changed and what's your intention?

This PR migrates additional aggregation tests from DuckDB to GreptimeDB’s suite to expand coverage of aggregation functions.

Remaining issues:

1. APPROX_DISTINCT does not accept null, date, or timestamp types. feat: support for null, date, and timestamp types in approx_distinct apache/datafusion#17618
2. corr(2, 2) incorrectly returns 0. fix(agg/corr): return NULL when variance is zero or samples < 2 apache/datafusion#17621
3. STRING_AGG(x, '|') fails with: “Invalid argument error: column types must match schema types, expected LargeUtf8 but found Utf8 at column index 0.” We convert LargeStringArray to StringVector, but build the final record batch with the original Arrow schema, causing schema validation to fail.

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.

[Copilot]

Pull Request Overview

This PR migrates additional aggregation test cases from DuckDB to GreptimeDB's test suite as part of the ongoing effort to improve test coverage for aggregation functions.

• Migrates 19 new test files covering various aggregate functions (string_agg, stddev, regression, min_max, median, etc.)
• Updates one existing result file with an error case for copy database operations
• Adds minor formatting improvement to one existing test file

Reviewed Changes

Copilot reviewed 34 out of 34 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/cases/standalone/common/copy/copy_database_from_fs_parquet.result	Updates test results with table not found errors for split_test table
tests/cases/standalone/common/aggregate/uddsketch.sql	Adds blank line for formatting consistency
tests/cases/standalone/common/aggregate/string_agg.sql	Migrates STRING_AGG function tests from DuckDB
tests/cases/standalone/common/aggregate/string_agg.result	Test results showing column type mismatch errors for STRING_AGG
tests/cases/standalone/common/aggregate/stddev.sql	Migrates standard deviation function tests
tests/cases/standalone/common/aggregate/stddev.result	Results for stddev_samp, stddev_pop, var_samp, var_pop functions
tests/cases/standalone/common/aggregate/regression.sql	Migrates regression analysis function tests
tests/cases/standalone/common/aggregate/regression.result	Results for regression slope, intercept, R2, and related functions
tests/cases/standalone/common/aggregate/min_max.sql	Migrates MIN/MAX aggregate function tests
tests/cases/standalone/common/aggregate/min_max.result	Results for MIN/MAX with various data types
tests/cases/standalone/common/aggregate/median.sql	Migrates MEDIAN aggregate function tests
tests/cases/standalone/common/aggregate/median.result	Results for median calculations with different data types
tests/cases/standalone/common/aggregate/first_last.sql	Migrates FIRST_VALUE and LAST_VALUE function tests
tests/cases/standalone/common/aggregate/first_last.result	Results for first/last value functions with ORDER BY
tests/cases/standalone/common/aggregate/covar.sql	Migrates covariance function tests
tests/cases/standalone/common/aggregate/covar.result	Results for COVAR_POP and COVAR_SAMP functions
tests/cases/standalone/common/aggregate/corr.sql	Migrates correlation coefficient function tests
tests/cases/standalone/common/aggregate/corr.result	Results for CORR function with various data patterns
tests/cases/standalone/common/aggregate/bool_agg.sql	Migrates boolean aggregation function tests
tests/cases/standalone/common/aggregate/bool_agg.result	Results for BOOL_AND and BOOL_OR functions
tests/cases/standalone/common/aggregate/bit_operations.sql	Migrates bitwise aggregation function tests
tests/cases/standalone/common/aggregate/bit_operations.result	Results for BIT_AND, BIT_OR, and BIT_XOR functions
tests/cases/standalone/common/aggregate/avg.sql	Migrates AVG aggregate function tests
tests/cases/standalone/common/aggregate/avg.result	Results for average calculations with type coercion errors
tests/cases/standalone/common/aggregate/array_agg.sql	Migrates array aggregation function tests
tests/cases/standalone/common/aggregate/array_agg.result	Results for ARRAY_AGG with ORDER BY and DISTINCT
tests/cases/standalone/common/aggregate/approx_percentile_cont_with_weight.sql	Migrates weighted approximate percentile tests
tests/cases/standalone/common/aggregate/approx_percentile_cont_with_weight.result	Results for weighted percentile calculations
tests/cases/standalone/common/aggregate/approx_percentile_cont.sql	Migrates approximate percentile function tests
tests/cases/standalone/common/aggregate/approx_percentile_cont.result	Results for APPROX_PERCENTILE_CONT function
tests/cases/standalone/common/aggregate/approx_median.sql	Migrates approximate median function tests
tests/cases/standalone/common/aggregate/approx_median.result	Results for APPROX_MEDIAN function
tests/cases/standalone/common/aggregate/approx_distinct.sql	Migrates approximate distinct count tests
tests/cases/standalone/common/aggregate/approx_distinct.result	Results for APPROX_DISTINCT function

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[Copilot]

Pull Request Overview

Copilot reviewed 33 out of 33 changed files in this pull request and generated 1 comment.

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[killme2008]

Ready to review.

Remaining issues:

1. APPROX_DISTINCT does not accept null, date, or timestamp types. feat: support for null, date, and timestamp types in approx_distinct apache/datafusion#17618
2. corr(2, 2) incorrectly returns 0. fix(agg/corr): return NULL when variance is zero or samples < 2 apache/datafusion#17621
3. STRING_AGG(x, '|') fails with: Invalid argument error: column types must match schema types, expected LargeUtf8 but found Utf8 at column index 0. We convert LargeStringArray to StringVector, but build the final record batch with the original Arrow schema, causing schema validation to fail. @evenyag We should remove all vector and data type conversions in the read path.

@discord9 @waynexia

[fengjiachun]

LGTM