Version and Platform Compatibility / Previous PostgreSQL Versions

array_nulls

• What it does: Controls whether NULL elements are allowed in array input values and how they are interpreted.
• Why it matters: This parameter affects how arrays with NULL values are handled during input and processing. When enabled, unquoted NULL in array input is treated as a true null value. When disabled, NULL is treated as a literal string. This is important for applications that rely on specific array null handling behavior, particularly when migrating from older PostgreSQL versions or other database systems with different array semantics.
• Ideal value & Best Practice: Default on is recommended for new applications. Set to off only if you need backward compatibility with very old PostgreSQL versions (pre-8.2) or have applications that expect the legacy behavior. For most modern applications, keeping this enabled provides better SQL standard compliance.

backslash_quote

• What it does: Controls whether backslash-escaping of single quotes (') is allowed in string literals.
• Why it matters: This parameter addresses a historical compatibility issue with string literal handling. Older PostgreSQL versions allowed backslash escaping in regular strings, but this was non-standard behavior. The SQL standard requires using two single quotes ('') for escaping within strings. This setting helps maintain compatibility with applications written for older PostgreSQL versions or other database systems that use backslash escaping.
• Ideal value & Best Practice: Default safe_encoding (allows except in client encoding that allows backslashes). For new applications, avoid relying on backslash escaping. Set to on only for legacy application compatibility. Use standard SQL quoting (two single quotes) for new development.

escape_string_warning

• What it does: Generates warnings when backslash escapes are used in ordinary string literals.
• Why it matters: This parameter helps identify non-standard string literal usage that may cause compatibility issues. Backslash escapes in regular strings are non-standard SQL and may be interpreted differently in future versions or other database systems. The warnings help developers identify and fix these compatibility issues before they become problems.
• Ideal value & Best Practice: Default on is recommended. Keep enabled to catch potential compatibility issues during development. The warnings help identify code that should use escape string syntax (E'...') or standard SQL quoting instead of backslash escapes.

lo_compat_privileges

• What it does: Enables backward compatibility mode for large object privilege checking, skipping privilege checks for reading or modifying large objects.
• Why it matters: This parameter addresses a significant security change introduced in PostgreSQL 9.0. Prior versions did not have privilege checks for large objects, which could create security vulnerabilities. Enabling this mode disables the security checks added in 9.0, providing compatibility with applications written for older versions but potentially creating security risks.
• Ideal value & Best Practice: Default off is strongly recommended for security. Enable only temporarily during migration from pre-9.0 versions. Always update applications to use proper large object privileges rather than relying on this compatibility mode long-term.

quote_all_identifiers

• What it does: Forces all identifiers to be quoted when generating SQL fragments.
• Why it matters: This parameter affects how PostgreSQL handles identifier case sensitivity and special characters. When enabled, all identifiers are quoted, making them case-sensitive and allowing special characters that would otherwise be invalid. This can be important for compatibility with applications or tools that expect specific quoting behavior.
• Ideal value & Best Practice: Default off is appropriate for most applications. Enable only if you need to preserve case sensitivity in identifiers or have special character requirements. Be aware that quoted identifiers can make SQL code less portable and more difficult to read.

standard_conforming_strings

• What it does: Controls whether ordinary string literals ('...') treat backslashes literally rather than as escape characters.
• Why it matters: This is a crucial parameter for SQL standard compliance and string handling behavior. When enabled, backslashes in strings are treated as literal characters rather than escape sequences. This aligns with SQL standards and improves portability between different database systems. The change was made default in PostgreSQL 9.1.
• Ideal value & Best Practice: Default on is strongly recommended. This provides SQL standard compliance and better portability. Only disable if you need backward compatibility with very old applications that rely on the non-standard behavior. Use escape string syntax (E'...') when you need backslash escapes.

synchronize_seqscans

• What it does: Enables or disables synchronized sequential scans, which allows multiple concurrent scans to synchronize their progress through a table.
• Why it matters: This parameter affects the performance characteristics of sequential table scans. When enabled, concurrent sequential scans on the same table can coordinate to avoid reading the same disk pages multiple times, potentially reducing I/O overhead. However, this synchronization adds some coordination overhead.
• Ideal value & Best Practice: Default on is generally beneficial. Disable only if you experience performance issues with concurrent sequential scans or for testing purposes. For most workloads, the synchronization provides better overall performance by reducing redundant I/O.

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