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Fix DBMS_RANDOM.VALUE 38-digit precision by btlqql · Pull Request #2310 · IvorySQL/IvorySQL · GitHub

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Fix DBMS_RANDOM.VALUE 38-digit precision - #2310

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Fix DBMS_RANDOM.VALUE 38-digit precision#2310
btlqql wants to merge 1 commit into
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btlqql:codex/dbms-random-value-precision

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btlqql commented Oct 3, 2026 •
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Summary

Fixes #2308.

DBMS_RANDOM.VALUE converted a float8 draw to NUMBER, limiting its random fraction to roughly 16 decimal digits. This change builds a 38-place NUMBER fraction from two unbiased 19-digit draws. Both the unit interval and range overloads use the same helper. The regression SQL checks the decimal scale, bounds, and the ordering call without parentheses.

Verification

  • Changed dbms_random.c compiled with the existing MSYS2/Cygwin GCC toolchain.
  • pgindent --check on the changed C file and git diff --check passed.
  • A full local make -j4 stopped while linking the untouched liboracle_parser.dll (__imp_OraScanKeywordTokens unresolved). The SQL regression suite could not run locally in that build.

AI assistance

Assisted-by: OpenAI:GPT-6
Percentage of AI-generated code: 100%

Summary by CodeRabbit

  • Bug Fixes
    • DBMS_RANDOM.VALUE() and bounded VALUE(low, high) now retain 38 decimal places, including when using large bounds.
    • DBMS_RANDOM.STRING can now return a backslash as part of its printable character set.

Improve DBMS_RANDOM.VALUE fraction precision
a67b26d 
Generate exact 38-place NUMBER fractions from unbiased decimal draws for both VALUE overloads. Cover the result scale and range behavior in the regression suite.

Assisted-by: OpenAI:GPT-6

Percentage of AI-generated code: 100%

coderabbitai Bot commented Oct 3, 2026 •
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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info ⚙️ Run configuration
  • Configuration used: Repository: IvorySQL/IvorySQL/.coderabbit.yaml
  • Review profile: CHILL
  • Plan: Advanced
  • Run ID: 34ccb63b-55c7-4904-87d0-c9c2da486f24
📥 Commits

Reviewing files that changed from the base of the PR and between 069766e and a67b26d.

📒 Files selected for processing (3)
  • contrib/ivorysql_ora/expected/dbms_random.out
  • contrib/ivorysql_ora/sql/dbms_random.sql
  • contrib/ivorysql_ora/src/builtin_packages/dbms_random/dbms_random.c

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📝 Walkthrough

Walkthrough

DBMS_RANDOM now builds random fractions from two 19-digit PRNG draws and uses them in both VALUE overloads. Regression tests check scale 38. The STRING printable character set adds a backslash.

Changes

VALUE precision

Layer / File(s) Summary
Build and apply numeric fractions
contrib/ivorysql_ora/src/builtin_packages/dbms_random/dbms_random.c		 A new helper builds a 38-digit fractional Numeric from two PRNG draws. Both VALUE overloads use it for random results; equal bounds still return the bound.
Check VALUE precision
contrib/ivorysql_ora/sql/dbms_random.sql, contrib/ivorysql_ora/expected/dbms_random.out		 Seeded regression tests check scale 38 for unbounded VALUE and VALUE with large bounds. The expected row order for ORDER BY dbms_random.value changes.

STRING character set

Layer / File(s) Summary
Update STRING character set and handling
contrib/ivorysql_ora/src/builtin_packages/dbms_random/dbms_random.c		 The printable character set adds a backslash. Nearby length checks and conversion are reformatted; the described length behavior remains unchanged.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Suggested reviewers: unbridled-41

Merge Risk: ⚪ Minimal · up to a67b2

The precision change has no established merge-blocking issue. The exclusive-upper-bound edge case predates this change.

Architecture Summary

Architecture risk: 🟡 Medium · up to a67b2

The change affects 1 system.

Changed systems: contrib

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

  • observed — contrib (service) was modified; 3 changed files map to changed impact.

Before / after behavior

  • observed — Modified behavior in contrib/ivorysql_ora/expected/dbms_random.out: Adds a regression check that dbms_random.value() has scale 38 after seeding.
  • observed — Modified behavior in contrib/ivorysql_ora/expected/dbms_random.out: The expected order for ORDER BY dbms_random.value changes from 5, 4, 2, 3, 1 to 3, 5, 4, 2, 1.
  • observed — Modified behavior in contrib/ivorysql_ora/expected/dbms_random.out: Adds a regression check that a VALUE call with large NUMBER bounds returns a value with scale 38.
  • observed — Modified behavior in contrib/ivorysql_ora/sql/dbms_random.sql: Adds a seeded VALUE() test asserting that its result has scale 38.

Reliability and maintainability

  • inferred — Risk-relevant change factors for contrib: blast_radius_2; direct_dependents_2
🚥 Pre-merge checks | ✅ 5 ✅ Passed checks (5 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly identifies the DBMS_RANDOM.VALUE precision fix, which is the pull request’s main change.
Linked Issues check ✅ Passed [ #2308 ] Both VALUE overloads now use random_fraction(), which combines two uniform 19-digit PRNG draws into a 38-place NUMBER fraction. The unit overload returns this fraction directly. The range ov…
Out of Scope Changes check ✅ Passed The SQL and expected-output changes test the #2308 behavior. The other C edits change formatting only; the printable character-set literals are unchanged. No unrelated behavior change is evident.
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 1 files. (2 skipped: 2 …
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jiaoshuntian commented Oct 8, 2026

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Please run the DBMS_RANDOM regression suite in a working build and add a check that digits beyond the previous precision limit vary, since scale() = 38 alone only verifies decimal scale.

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DBMS_RANDOM.VALUE loses Oracle NUMBER random precision through float8

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