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mmap
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mmap
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mmap
page1 page2 page3 page4
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mmap
page1 page2 page3 page4
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→
→ page_id offset/slot→
CTID (4-bytes)
ROWID (10-bytes)
ROWID (8-bytes)
→→
Header
Page
Data
Page
Data
Page
Data
Page
Data
…
…
→→→
Log File
…INSERT id=1,val=a
INSERT id=2,val=b
DELETE id=4
UPDATE val=X (id=3)
UPDATE val=Y (id=4)
INSERT id=3,val=c
Log File
INSERT id=1,val=a
INSERT id=2,val=b
DELETE id=4
UPDATE val=X (id=3)
UPDATE val=Y (id=4)
INSERT id=3,val=c
…
SELECT * FROM tableWHERE id = 1
Log File
INSERT id=1,val=a
INSERT id=2,val=b
DELETE id=4
UPDATE val=X (id=3)
UPDATE val=Y (id=4)
INSERT id=3,val=c
…id=1
id=2
id=3
id=4
SELECT * FROM tableWHERE id = 1
Log File
id=1,val=aid=2,val=bid=3,val=Xid=4,val=Y
→→
Header
Tuple #4
Tuple #2
Tuple #3
Tuple #1
→→
Header
Tuple #4
Tuple #2
Tuple #3
Tuple #1
Header a b c d e
CREATE TABLE foo (a INT PRIMARY KEY,b INT NOT NULL,c INT,d DOUBLE,e FLOAT
);
INTEGER BIGINT SMALLINT TINYINT→
FLOAT REAL NUMERIC DECIMAL→
VARCHAR VARBINARY TEXT BLOB→
TIME DATE TIMESTAMP→
→ FLOAT REAL DOUBLE
#include <stdio.h>
int main(int argc, char* argv[]) {float x = 0.1;float y = 0.2;printf("x+y = %.20f\n", x+y);printf("0.3 = %.20f\n", 0.3);
}
x+y = 0.300000011920928955080.3 = 0.29999999999999998890
typedef unsigned char NumericDigit;
typedef struct {
int ndigits;
int weight;
int scale;
int sign;
NumericDigit *digits;
} numeric;
typedef unsigned char NumericDigit;
typedef struct {
int ndigits;
int weight;
int scale;
int sign;
NumericDigit *digits;
} numeric;
→→
VARCHAR DATA
Header a b c d e
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