Many hyperlinks are disabled.
Use anonymous login
to enable hyperlinks.
Overview
Comment: | Documentation for SQLITE_ENABLE_SORTER_REFERENCES. |
---|---|
Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA3-256: |
183931a12198f95b0808cc1bc77c2b26 |
User & Date: | drh 2018-05-04 16:43:30.723 |
Context
2018-05-08
| ||
13:35 | Mention the cell-overwrite optimization on the change log. (check-in: d324d1a30e user: drh tags: trunk) | |
2018-05-04
| ||
16:43 | Documentation for SQLITE_ENABLE_SORTER_REFERENCES. (check-in: 183931a121 user: drh tags: trunk) | |
05:03 | Update the speed-and-size spreadsheet. (check-in: 0fdc011d0b user: drh tags: trunk) | |
Changes
Changes to pages/compile.in.
︙ | ︙ | |||
1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 | This option causes SQLite to include support for the [rtree | R*Tree index extension]. } COMPILE_OPTION {SQLITE_ENABLE_SESSION} { This option enables the [session extension]. } COMPILE_OPTION {SQLITE_ENABLE_STMT_SCANSTATUS} { This option enables the [sqlite3_stmt_scanstatus()] interface. The [sqlite3_stmt_scanstatus()] interface is normally omitted from the build because it imposes a small performance penalty, even on statements that do not use the feature. } | > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 | This option causes SQLite to include support for the [rtree | R*Tree index extension]. } COMPILE_OPTION {SQLITE_ENABLE_SESSION} { This option enables the [session extension]. } COMPILE_OPTION {SQLITE_ENABLE_SORTER_REFERENCES} { This option activates an optimization that reduces the memory required by the sorter at the cost of doing additional B-tree lookups after the sort has occurred. <p> The default sorting procedure is to gather all information that will ultimately be output into a "record" and pass that complete record to the sorter. But in some cases, for example if some of the output columns consists of large BLOB values, the size of the each record can be large, which means that the sorter has to either use more memory, and/or write more content to temporary storage. <p> When SQLITE_ENABLE_SORTER_PREFERENCES is enabled, the records passed to the sorter often contain only a [ROWID] value. Such records are much smaller. This means the sorter has much less "payload" to deal with and can run faster. After sorting has occurred, the ROWID is used to look up the output column values in the original table. That requires another search into the table, and could potentially result in a slowdown. Or, it might be a performance win, depending on how large the values are. <p> Even when the SQLITE_ENABLE_SORTER_PREFERENCES compile-time option is on, sorter references are still disabled by default. To use sorter references, the application must set a sorter reference size threshold using the [sqlite3_config]([SQLITE_CONFIG_SORTERREF_SIZE]) interface at start-time. <p> Because the SQLite developers do not know whether the SQLITE_ENABLE_SORTER_PERFERENCES option will help or hurt performance, it is disabled by default at this time (2018-05-04). It might be enabled by default in some future release, depending on what is learned about its inpact on performance. } COMPILE_OPTION {SQLITE_ENABLE_STMT_SCANSTATUS} { This option enables the [sqlite3_stmt_scanstatus()] interface. The [sqlite3_stmt_scanstatus()] interface is normally omitted from the build because it imposes a small performance penalty, even on statements that do not use the feature. } |
︙ | ︙ |