Name | Effect | Values |
allocation_size | the file unit allocation size, in bytes, must a power-of-two; smaller values decrease the file space required by overflow items, and the default value of 512B is a good choice absent requirements from the operating system or storage device. | an integer between 512B and 128MB; default 512B . |
block_compressor | configure a compressor for file blocks. Permitted values are empty (off) or "bzip2" , "snappy" or custom compression engine "name" created with WT_CONNECTION::add_compressor. See Compressors for more information. | a string; default empty. |
cache_resident | do not ever evict the object's pages; see Cache resident objects for more information. | a boolean flag; default false . |
checksum | configure file block checksums; permitted values are on (checksum all file blocks), off (checksum no file blocks) and uncompresssed (checksum only file blocks which are not compressed for some reason). The uncompressed value is for applications which can reasonably rely on decompression to fail if a block has been corrupted. | a string, chosen from the following options: "on" , "off" , "uncompressed" ; default on . |
colgroups | comma-separated list of names of column groups. Each column group is stored separately, keyed by the primary key of the table. If no column groups are specified, all columns are stored together in a single file. All value columns in the table must appear in at least one column group. Each column group must be created with a separate call to WT_SESSION::create. | a list of strings; default empty. |
collator | configure custom collation for keys. Value must be a collator name created with WT_CONNECTION::add_collator. | a string; default empty. |
columns | list of the column names. Comma-separated list of the form (column[,...]) . For tables, the number of entries must match the total number of values in key_format and value_format . For colgroups and indices, all column names must appear in the list of columns for the table. | a list of strings; default empty. |
dictionary | the maximum number of unique values remembered in the Btree row-store leaf page value dictionary; see File formats and compression for more information. | an integer greater than or equal to 0; default 0 . |
exclusive | fail if the object exists. When false (the default), if the object exists, check that its settings match the specified configuration. | a boolean flag; default false . |
format | the file format. | a string, chosen from the following options: "btree" ; default btree . |
huffman_key | configure Huffman encoding for keys. Permitted values are empty (off), "english" , "utf8<file>" or "utf16<file>" . See Huffman Encoding for more information. | a string; default empty. |
huffman_value | configure Huffman encoding for values. Permitted values are empty (off), "english" , "utf8<file>" or "utf16<file>" . See Huffman Encoding for more information. | a string; default empty. |
internal_item_max | the maximum key size stored on internal nodes, in bytes. If zero, a maximum is calculated to permit at least 8 keys per internal page. | an integer greater than or equal to 0; default 0 . |
internal_key_truncate | configure internal key truncation, discarding unnecessary trailing bytes on internal keys (ignored for custom collators). | a boolean flag; default true . |
internal_page_max | the maximum page size for internal nodes, in bytes; the size must be a multiple of the allocation size and is significant for applications wanting to avoid excessive L2 cache misses while searching the tree. The page maximum is the bytes of uncompressed data, that is, the limit is applied before any block compression is done. | an integer between 512B and 512MB; default 2KB . |
key_format | the format of the data packed into key items. See Format types for details. By default, the key_format is 'u' and applications use WT_ITEM structures to manipulate raw byte arrays. By default, records are stored in row-store files: keys of type 'r' are record numbers and records referenced by record number are stored in column-store files. | a format string; default u . |
key_gap | the maximum gap between instantiated keys in a Btree leaf page, constraining the number of keys processed to instantiate a random Btree leaf page key. | an integer greater than or equal to 0; default 10 . |
leaf_item_max | the maximum key or value size stored on leaf nodes, in bytes. If zero, a size is calculated to permit at least 8 items (values or row store keys) per leaf page. | an integer greater than or equal to 0; default 0 . |
leaf_page_max | the maximum page size for leaf nodes, in bytes; the size must be a multiple of the allocation size, and is significant for applications wanting to maximize sequential data transfer from a storage device. The page maximum is the bytes of uncompressed data, that is, the limit is applied before any block compression is done. | an integer between 512B and 512MB; default 1MB . |
lsm_bloom | create bloom filters on LSM tree chunks as they are merged. | a boolean flag; default true . |
lsm_bloom_bit_count | the number of bits used per item for LSM bloom filters. | an integer between 2 and 1000; default 8 . |
lsm_bloom_config | config string used when creating Bloom filter files, passed to WT_SESSION::create. | a string; default empty. |
lsm_bloom_hash_count | the number of hash values per item used for LSM bloom filters. | an integer between 2 and 100; default 4 . |
lsm_bloom_newest | create a bloom filter on an LSM tree chunk before it's first merge. Only supported if bloom filters are enabled. | a boolean flag; default false . |
lsm_bloom_oldest | create a bloom filter on the oldest LSM tree chunk. Only supported if bloom filters are enabled. | a boolean flag; default false . |
lsm_chunk_size | the maximum size of the in-memory chunk of an LSM tree. | an integer between 512K and 500MB; default 2MB . |
lsm_merge_max | the maximum number of chunks to include in a merge operation. | an integer between 2 and 100; default 15 . |
lsm_merge_threads | the number of thread to perform merge operations. | an integer between 1 and 10; default 1 . |
memory_page_max | the maximum size a page can grow to in memory before being reconciled to disk. The specified size will be adjusted to a lower bound of 50 * leaf_page_max . This limit is soft - it is possible for pages to be temporarily larger than this value. | an integer between 512B and 10TB; default 5MB . |
prefix_compression | configure row-store format key prefix compression. | a boolean flag; default true . |
source | override the default data source URI derived from the object name. | a string; default empty. |
split_pct | the Btree page split size as a percentage of the maximum Btree page size, that is, when a Btree page is split, it will be split into smaller pages, where each page is the specified percentage of the maximum Btree page size. | an integer between 25 and 100; default 75 . |
type | set the data source type. This setting overrides the URI prefix for the data source, if no source configuration setting is provided. | a string, chosen from the following options: "file" , "lsm" ; default file . |
value_format | the format of the data packed into value items. See Format types for details. By default, the value_format is 'u' and applications use a WT_ITEM structure to manipulate raw byte arrays. Value items of type 't' are bitfields, and when configured with record number type keys, will be stored using a fixed-length store. | a format string; default u . |