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Commit 7682a734 authored by Bradley C. Kuszmaul's avatar Bradley C. Kuszmaul
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Get rid of some junk. 

git-svn-id: file:///svn/tokudb@3571 c7de825b-a66e-492c-adef-691d508d4ae1
parent 53731aa7
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#if !defined(OMT_H)
#define OMT_H
#ident "Copyright (c) 2007 Tokutek Inc. All rights reserved."
// Order Maintenance Array (OMT)
//
// Maintains a collection of totally ordered values, where each value has an integer weight.
// The OMT is a mutable datatype.
//
// The Abstraction:
//
// An OMT is a vector of values, $V$, where $|V|$ is the length of the vector.
// The vector is numbered from $0$ to $|V|-1$.
// Each value has a weight. The weight of the $i$th element is denoted $w(V_i)$.
//
// We can create a new OMT, which is the empty vector.
//
// We can insert a new element $x$ into slot $i$, changing $V$ into $V'$ where
// $|V'|=1+|V|$ and
//
// V'_j = V_j if $j<i$
// x if $j=i$
// V_{j-1} if $j>i$.
//
// We can specify $i$ using a kind of function instead of as an integer.
// Let $b$ be a function mapping from values to nonzero integers, such that
// the signum of $b$ is monotically increasing.
// We can specify $i$ as the minimum integer such that $b(V_i)>0$.
//
// We look up a value using its index, or using a Heaviside function.
// For lookups, we allow $b$ to be zero for some values, and again the signum of $b$ must be monotonically increasing.
// When lookup up values, we can look up
// $V_i$ where $i$ is the minimum integer such that $b(V_i)=0$. (With a special return code if no such value exists.)
// (Rationale: Ordinarily we want $i$ to be unique. But for various reasons we want to allow multiple zeros, and we want the smallest $i$ in that case.)
// $V_i$ where $i$ is the minimum integer such that $b(V_i)>0$. (Or an indication that no such value exists.)
// $V_i$ where $i$ is the maximum integer such that $b(V_i)<0$. (Or an indication that no such value exists.)
//
// When looking up a value using a Heaviside function, we get the value and its index.
//
// We can also split an OMT into two OMTs, splitting the weight of the values evenly.
// Find a value $j$ such that the values to the left of $j$ have about the same total weight as the values to the right of $j$.
// The resulting two OMTs contain the values to the left of $j$ and the values to the right of $j$ respectively.
// All of the values from the original OMT go into one of the new OMTs.
// If the weights of the values don't split exactly evenly, then the implementation has the freedom to choose whether
// the new left OMT or the new right OMT is larger.
//
// Performance:
// Insertion and deletion should run with $O(\log |V|)$ time and $O(\log |V|)$ calls to the Heaviside function.
// The memory required is O(|V|).
//
// The programming API:
typedef struct value *OMTVALUE; // A slight improvement over using void*.
typedef struct omt *OMT;
int toku_omt_create (OMT *omtp);
// Effect: Create an empty OMT. Stores it in *omtp.
// Requires: omtp != NULL
// Returns:
// 0 success
// ENOMEM out of memory (and doesn't modify *omtp)
// Performance: constant time.
int toku_omt_create_from_sorted_array(OMT* omtp, OMTVALUE *values, u_int32_t numvalues);
// Effect: Create a OMT containing values. The number of values is in numvalues.
// Stores the new OMT in *omtp.
// Requires: omtp != NULL
// Requires: values != NULL
// Returns:
// 0 success
// ENOMEM out of memory (and doesn't modify *omtp)
// Performance: time=O(numvalues)
// Rational: Normally to insert N values takes O(N lg N) amortized time.
// If the N values are known in advance, are sorted, and
// the structure is empty, we can batch insert them much faster.
// Hack: Can be temporarily implemented in O(numvalues * lg numvalues)
// by wrapping toku_omt_create and repeated toku_omt_insert_at
// until we have time to implement properly.
void toku_omt_destroy(OMT *omtp);
// Effect: Destroy an OMT, freeing all its memory.
// Does not free the OMTVALUEs stored in the OMT.
// Those values may be freed before or after calling toku_omt_destroy.
// Also sets *omtp=NULL.
// Requires: omtp != NULL
// Requires: *omtp != NULL
// Rationale: The usage is to do something like
// toku_omt_destroy(&s->omt);
// and now s->omt will have a NULL pointer instead of a dangling freed pointer.
// Rationale: Returns no values since free() cannot fail.
// Rationale: Does not free the OMTVALUEs to reduce complexity.
// Performance: time=O(toku_omt_size(*omtp))
u_int32_t toku_omt_size(OMT V);
// Effect: return |V|.
// Requires: V != NULL
// Performance: time=O(1)
int toku_omt_iterate(OMT omt, int (*f)(OMTVALUE, u_int32_t, void*), void*v);
// Effect: Iterate over the values of the omt, from left to right, calling f on each value.
// The second argument passed to f is the index of the value.
// The third argument passed to f is v.
// The indices run from 0 (inclusive) to toku_omt_size(omt) (exclusive).
// Requires: omt != NULL
// Requires: f != NULL
// Returns:
// If f ever returns nonzero, then the iteration stops, and the value returned by f is returned by toku_omt_iterate.
// If f always returns zero, then toku_omt_iterate returns 0.
// Requires: Don't modify omt while running. (E.g., f may not insert or delete values form omt.)
// Performance: time=O(i+\log N) where i is the number of times f is called, and N is the number of elements in omt.
// Rational: Although the functional iterator requires defining another function (as opposed to C++ style iterator), it is much easier to read.
int toku_omt_insert_at(OMT omt, OMTVALUE value, u_int32_t index);
// Effect: Increases indexes of all items at slot >= index by 1.
// Insert value into the position at index.
// Requires: omt != NULL
// Requires: value != NULL
//
// Returns:
// 0 success
// ERANGE if index>toku_omt_size(omt)
// ENOMEM
// On error, omt is unchanged.
// Performance: time=O(\log N) amortized time.
// Rationale: Some future implementation may be O(\log N) worst-case time, but O(\log N) amortized is good enough for now.
int toku_omt_insert(OMT omt, OMTVALUE value, int(*h)(OMTVALUE, void*v), void *v, u_int32_t* index);
// Effect: Insert value into the OMT.
// If there is some i such that $h(V_i, v)=0$ then returns DB_KEYEXIST.
// Otherwise, let i be the minimum value such that $h(V_i, v)>0$.
// If no such i exists, then let i be |V|
// Then this has the same effect as
// oma_insert_at(tree, value, i);
// i is stored in *index
// Requires: omt != NULL
// Requires: value != NULL
// Requires: index != NULL
// Requires: The signum of h must be monotonically increasing.
// Returns:
// 0 success
// DB_KEYEXIST the key is present (h was equal to zero for some value)
// ENOMEM
// On nonzero return, omt is unchanged.
// On nonzero non-DB_KEYEXIST return, *index is unchanged.
// Performance: time=O(\log N) amortized.
// Rationale: Some future implementation may be O(\log N) worst-case time, but O(\log N) amortized is good enough for now.
int toku_omt_delete_at(OMT omt, u_int32_t index);
// Effect: Delete the item in slot index.
// Decreases indexes of all items at slot >= index by 1.
// Requires: omt != NULL
// Returns
// 0 success
// ERANGE if index>=toku_omt_size(omt)
// On error, omt is unchanged.
// Rationale: To delete an item, first find its index using toku_omt_find, then delete it.
// Performance: time=O(\log N) amortized.
int toku_omt_find_index (OMT V, u_int32_t i, VALUE *v);
// Effect: Set *v=V_i
// Requires: omt != NULL
// Requires: v != NULL
// Returns
// 0 success
// ERANGE if i out of range
// On nonzero return, *v is unchanged.
// Performance: time=O(\log N)
int toku_omt_find(OMT V, int (*h)(VALUE, void*extra), void*extra, int direction, VALUE *value, u_int32_t *index);
// Effect:
// If direction==0 then find the smallest i such that h(V_i,extra)==0.
// If direction >0 then find the smallest i such that h(V_i,extra)>0.
// If direction <0 then find the largest i such that h(V_i,extra)<0.
// store V_i in *value
// store i in *index
// Requires: V != NULL
// Requires: h != NULL
// Requires: value != NULL
// Requires: index != NULL
// Returns
// 0 success
// DB_NOTFOUND no such value is found.
// On nonzero return, *value and *index are unchanged.
// Performance: time=O(\log N)
int toku_omt_split_at(OMT omt, OMT *newoma, u_int32_t index);
// Effect: Create a new OMT, storing it in *newoma.
// The values to the right of index (starting at index) are moved to *newoma.
// Requires: omt != NULL
// Requires: newoma != NULL
// Returns
// 0 success,
// ERANGE if index >= toku_omt_size(omt)
// ENOMEM
// On nonzero return, omt and *newoma are unmodified.
// Performance: time=O(n)
// Rationale: We don't need a split-evenly operation. We need to split items so that their total sizes
// are even, and other similar splitting criteria. It's easy to split evenly by calling toku_omt_size(), and dividing by two.
int toku_omt_merge(OMT leftoma, OMT rightoma, OMT *newoma);
// Effect: Appends leftoma and rightoma to produce a new omt.
// Sets *newoma to the new omt.
// leftoma and rightoma are left unchanged.
// Requires: leftoma != NULL
// Requires: rightoma != NULL
// Requires: newoma != NULL
// Returns 0 on success
// ENOMEM on out of memory.
// On error, nothing is modified.
// Performance: time=O(n) is acceptable, but one can imagine implementations that are O(\log n) worst-case.
#endif /* #ifndef OMT_H */
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