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Performance optimization to the lookaside-memory disabling mechanism.

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FossilOrigin-Name: 17ce1c49cb0ed6fdd8c7c33431bc2afa217f1092c99b8dd608890a8e7aec7fb1
This commit is contained in:
drh
2019-10-05 14:39:36 +00:00
parent 228a52d973
commit 31f69626df
10 changed files with 58 additions and 47 deletions
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11
src/sqliteInt.h
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@@ -1271,10 +1271,17 @@ struct Schema {
** is shared by multiple database connections. Therefore, while parsing
** schema information, the Lookaside.bEnabled flag is cleared so that
** lookaside allocations are not used to construct the schema objects.
**
** New lookaside allocations are only allowed if bDisable==0. When
** bDisable is greater than zero, sz is set to zero which effectively
** disables lookaside without adding a new test for the bDisable flag
** in a performance-critical path. sz should be set by to szTrue whenever
** bDisable changes back to zero.
*/
struct Lookaside {
u32 bDisable; /* Only operate the lookaside when zero */
u16 sz; /* Size of each buffer in bytes */
u16 szTrue; /* True value of sz, even if disabled */
u8 bMalloced; /* True if pStart obtained from sqlite3_malloc() */
u32 nSlot; /* Number of lookaside slots allocated */
u32 anStat[3]; /* 0: hits. 1: size misses. 2: full misses */
@@ -1287,6 +1294,10 @@ struct LookasideSlot {
LookasideSlot *pNext; /* Next buffer in the list of free buffers */
};
#define DisableLookaside db->lookaside.bDisable++;db->lookaside.sz=0
#define EnableLookaside db->lookaside.bDisable--;\
db->lookaside.sz=db->lookaside.bDisable?0:db->lookaside.szTrue
/*
** A hash table for built-in function definitions. (Application-defined
** functions use a regular table table from hash.h.)