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Comment:Document the SQLITE_QUERY_PLANNER_LIMIT and SQLITE_QUERY_PLANNER_LIMIT_INCR compile-time options.
Timelines: family | ancestors | descendants | both | trunk
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SHA3-256: 55fce17e3c1bc014657664e941ec8c996e5fd141e0864b67096e78c5aafe02b2
User & Date: drh 2018-09-24 12:40:44
Context
2018-09-26
15:19
Merge changes from the 3.25 branch. check-in: 2e3a732177 user: drh tags: trunk
2018-09-24
12:40
Document the SQLITE_QUERY_PLANNER_LIMIT and SQLITE_QUERY_PLANNER_LIMIT_INCR compile-time options. check-in: 55fce17e3c user: drh tags: trunk
2018-09-21
10:16
Fix a harmless typo in the json documentation. check-in: 2bdb2d7e21 user: drh tags: trunk
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  Setting SQLITE_POWERSAFE_OVERWRITE to 1 causes SQLite to assume that
  application-level writes cannot changes bytes outside the range of
  bytes written even if the write occurs just before a power loss.
  With SQLITE_POWERSAFE_OVERWRITE set to 0, SQLite assumes that other
  bytes in the same sector with a written byte might be changed or 
  damaged by a power loss.
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COMPILE_OPTION {SQLITE_REVERSE_UNORDERED_SELECTS} {
  This option causes the [PRAGMA reverse_unordered_selects] setting to be
  enabled by default.  When enabled, [SELECT] statements that lack an
  ORDER BY clause will run in reverse order.<p>
  This option is useful for detecting when applications (incorrectly)
  assume that the order of rows in a SELECT without an ORDER BY clause







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  Setting SQLITE_POWERSAFE_OVERWRITE to 1 causes SQLite to assume that
  application-level writes cannot changes bytes outside the range of
  bytes written even if the write occurs just before a power loss.
  With SQLITE_POWERSAFE_OVERWRITE set to 0, SQLite assumes that other
  bytes in the same sector with a written byte might be changed or 
  damaged by a power loss.
}

COMPILE_OPTION {SQLITE_QUERY_PLANNER_LIMIT=<i>N</i>} {
  As part of the query planning process, SQLite enumerates all usable
  combinations of indexes and WHERE-clause constraints.  For certain
  pathological queries, the number of these index-and-constraint combinations
  can be very large, resulting in slow performance by the query planner.
  The SQLITE_QUERY_PLANNER_LIMIT value (in conjunction with the
  related [SQLITE_QUERY_PLANNER_LIMIT_INCR] setting) limits the number 
  of index-and-constraint combinations that the query planner will 
  consider, in order to prevent the query planner from using excess
  CPU time.  The default value for SQLITE_QUERY_PLANNER_LIMIT is set
  high enough so that is never reached for real-world queries.  The
  query planner search limit only applies to queries that are deliberately
  crafted to use excess planning time.
}

COMPILE_OPTION {SQLITE_QUERY_PLANNER_LIMIT_INCR=<i>N</i>} {
  The [SQLITE_QUERY_PLANNER_LIMIT] option sets an initial baseline value
  for the maximum number of index-and-constraint combinations that the
  query planner consider.  The baseline query planner limit is increased
  by SQLITE_QUERY_PLANNER_LIMIT_INCR prior to processing each table of a
  join so that each table is guaranteed to be able to propose at least
  some index-and-constraint combinations to the optimizer even if prior
  tables of the join have exhausted the baseline limit.  The default
  value for both this compile-time option and the
  [SQLITE_QUERY_PLANNER_LIMIT] option are set high enough so that they should
  never be reached for real-world queries.
}

COMPILE_OPTION {SQLITE_REVERSE_UNORDERED_SELECTS} {
  This option causes the [PRAGMA reverse_unordered_selects] setting to be
  enabled by default.  When enabled, [SELECT] statements that lack an
  ORDER BY clause will run in reverse order.<p>
  This option is useful for detecting when applications (incorrectly)
  assume that the order of rows in a SELECT without an ORDER BY clause