diff options
Diffstat (limited to 'src/sqliteInt.h')
| -rw-r--r-- | src/sqliteInt.h | 71 |
1 files changed, 60 insertions, 11 deletions
diff --git a/src/sqliteInt.h b/src/sqliteInt.h index 6eb07b7c6..d936b2c30 100644 --- a/src/sqliteInt.h +++ b/src/sqliteInt.h @@ -1297,6 +1297,25 @@ struct Schema { ** 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. +** +** Lookaside buffers are initially held on the pInit list. As they are +** used and freed, they are added back to the pFree list. New allocations +** come off of pFree first, then pInit as a fallback. This dual-list +** allows use to compute a high-water mark - the maximum number of allocations +** outstanding at any point in the past - by subtracting the number of +** allocations on the pInit list from the total number of allocations. +** +** Enhancement on 2019-12-12: Two-size-lookaside +** The default lookaside configuration is 100 slots of 1200 bytes each. +** The larger slot sizes are important for performance, but they waste +** a lot of space, as most lookaside allocations are less than 128 bytes. +** The two-size-lookaside enhancement breaks up the lookaside allocation +** into two pools: One of 128-byte slots and the other of the default size +** (1200-byte) slots. Allocations are filled from the small-pool first, +** failing over to the full-size pool if that does not work. Thus more +** lookaside slots are available while also using less memory. +** This enhancement can be omitted by compiling with +** SQLITE_OMIT_TWOSIZE_LOOKASIDE. */ struct Lookaside { u32 bDisable; /* Only operate the lookaside when zero */ @@ -1307,6 +1326,12 @@ struct Lookaside { u32 anStat[3]; /* 0: hits. 1: size misses. 2: full misses */ LookasideSlot *pInit; /* List of buffers not previously used */ LookasideSlot *pFree; /* List of available buffers */ +#ifndef SQLITE_OMIT_TWOSIZE_LOOKASIDE + LookasideSlot *pSmallInit; /* List of small buffers not prediously used */ + LookasideSlot *pSmallFree; /* List of available small buffers */ + void *pMiddle; /* First byte past end of full-size buffers and + ** the first byte of LOOKASIDE_SMALL buffers */ +#endif /* SQLITE_OMIT_TWOSIZE_LOOKASIDE */ void *pStart; /* First byte of available memory space */ void *pEnd; /* First byte past end of available space */ }; @@ -1318,6 +1343,13 @@ struct LookasideSlot { #define EnableLookaside db->lookaside.bDisable--;\ db->lookaside.sz=db->lookaside.bDisable?0:db->lookaside.szTrue +/* Size of the smaller allocations in two-size lookside */ +#ifdef SQLITE_OMIT_TWOSIZE_LOOKASIDE +# define LOOKASIDE_SMALL 0 +#else +# define LOOKASIDE_SMALL 128 +#endif + /* ** A hash table for built-in function definitions. (Application-defined ** functions use a regular table table from hash.h.) @@ -2692,23 +2724,28 @@ struct Expr { ** also be used as the argument to a function, in which case the a.zName ** field is not used. ** -** By default the Expr.zSpan field holds a human-readable description of -** the expression that is used in the generation of error messages and -** column labels. In this case, Expr.zSpan is typically the text of a -** column expression as it exists in a SELECT statement. However, if -** the bSpanIsTab flag is set, then zSpan is overloaded to mean the name -** of the result column in the form: DATABASE.TABLE.COLUMN. This later -** form is used for name resolution with nested FROM clauses. +** In order to try to keep memory usage down, the Expr.a.zEName field +** is used for multiple purposes: +** +** eEName Usage +** ---------- ------------------------- +** ENAME_NAME (1) the AS of result set column +** (2) COLUMN= of an UPDATE +** +** ENAME_TAB DB.TABLE.NAME used to resolve names +** of subqueries +** +** ENAME_SPAN Text of the original result set +** expression. */ struct ExprList { int nExpr; /* Number of expressions on the list */ struct ExprList_item { /* For each expression in the list */ Expr *pExpr; /* The parse tree for this expression */ - char *zName; /* Token associated with this expression */ - char *zSpan; /* Original text of the expression */ + char *zEName; /* Token associated with this expression */ u8 sortFlags; /* Mask of KEYINFO_ORDER_* flags */ + unsigned eEName :2; /* Meaning of zEName */ unsigned done :1; /* A flag to indicate when processing is finished */ - unsigned bSpanIsTab :1; /* zSpan holds DB.TABLE.COLUMN */ unsigned reusable :1; /* Constant expression is reusable */ unsigned bSorterRef :1; /* Defer evaluation until after sorting */ unsigned bNulls: 1; /* True if explicit "NULLS FIRST/LAST" */ @@ -2723,6 +2760,13 @@ struct ExprList { }; /* +** Allowed values for Expr.a.eEName +*/ +#define ENAME_NAME 0 /* The AS clause of a result set */ +#define ENAME_SPAN 1 /* Complete text of the result set expression */ +#define ENAME_TAB 2 /* "DB.TABLE.NAME" for the result set */ + +/* ** An instance of this structure can hold a simple list of identifiers, ** such as the list "a,b,c" in the following statements: ** @@ -4461,7 +4505,12 @@ void sqlite3CodeRhsOfIN(Parse*, Expr*, int); int sqlite3CodeSubselect(Parse*, Expr*); void sqlite3SelectPrep(Parse*, Select*, NameContext*); void sqlite3SelectWrongNumTermsError(Parse *pParse, Select *p); -int sqlite3MatchSpanName(const char*, const char*, const char*, const char*); +int sqlite3MatchEName( + const struct ExprList_item*, + const char*, + const char*, + const char* +); int sqlite3ResolveExprNames(NameContext*, Expr*); int sqlite3ResolveExprListNames(NameContext*, ExprList*); void sqlite3ResolveSelectNames(Parse*, Select*, NameContext*); |